JP2013214353A - Magnetic recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide solution means that realizes multilayer recording and multi-value recording in a magnetic recording device.SOLUTION: A magnetic recording device comprises: a magnetic storage medium including a plurality of recording layers having magnetic resonance frequencies different from one another; a magnetic recording head for writing information to the magnetic recording medium; and a magnetic reproduction head for reading the information from the magnetic recording medium. The magnetic recording head includes a high-frequency oscillation element magnetically assisting writing of the information with respect to at least one layer of the plurality of recording layers. The high-frequency oscillation element is configured so as to selectively change magnetization of at least one layer of the recording layers by applying a high frequency thereto. The high frequency is substantially equal to the magnetic resonance frequency of at least one layer of the recording layers.

Description

  The present invention relates to a magnetic recording apparatus capable of multi-value recording.

  The progress in increasing the density and capacity of magnetic recording devices (Hard Disk Drive) has greatly contributed to the progress of not only PCs and servers, but also portable music / video players and video recorders. The widespread use of magnetic recording devices greatly depends on whether a large capacity can be realized. The technical key point for realizing large capacity is how to achieve high density recording.

As an index of recording density, the number of bits per square inch, that is, a unit of bit / inch ² (bpsi) is used. Up to now, the recording density has been improved by reducing the size per bit. When such a technique for reducing the bit size is used, when the recording density reaches several Tbpsi, the size of one side per bit becomes 10 nm or less.

  However, it is obvious that there is a limit to continuously reducing the size of 1 bit by extending the conventional technology. An example of the reason is shown below.

  In order to read a small bit, the element size of the magnetic head must be reduced, but the element size depends on the minimum line width limit of the lithography technique. Even if the lithography technology advances, if the bit size is reduced, there will be a problem of thermal fluctuation of the medium, making it difficult to hold bit information. Further, even if a medium made of a material having high magnetic anisotropy can be realized, it is difficult to invert the bits by the magnetic head, that is, to perform recording. Furthermore, when one bit is 10 nm or less, the total number of atoms forming one bit decreases, and it becomes difficult to show the original characteristics of the material. In other words, even a highly magnetic anisotropy material that is feasible at about 20-30 nm is likely to become unusable in the region of 10 nm or less.

  As described above, in the technique of continuously reducing the size of 1 bit with the current extension technology, the limit of the density increase of the magnetic recording apparatus comes and the limit of the storage device comes.

  As described above, it is obvious that the physical limit is reached only by increasing the density by reducing the bit size. As a high-density method that does not rely only on bit miniaturization, it is conceivable to perform multi-value recording / multi-layer recording. Multi-level / multi-layer recording is a technique already performed in a semiconductor memory. If this can be realized also in magnetic recording, even in the same occupied area as the conventional 1 bit / 1 pattern, an improvement in recording density can be realized by using multiple values or multiple layers.

  However, in magnetic recording, it is not easy to realize multilevel recording / multilayer recording more than semiconductor memory.

  First, considering the situation of multilayer recording, in a semiconductor memory, a state in which electrical wiring is connected to each multilayered element is realized, and a current is selectively passed to the wiring to each element. By doing so, multilayer recording can be realized. Although it is difficult to realize multilayer wiring from the viewpoint of microfabrication technology, the selection of each element becomes possible in principle due to the presence of electrical wiring.

  However, in the magnetic recording apparatus, there is no concept of magnetic wiring between the magnetic head and the medium, and there is only a space. In such a situation, it is impossible to select each bit by wiring. If an attempt is made to write to a bit that is far from the head, information is simultaneously written to a bit that is closer than that bit. As a result, selective writing cannot be performed. In other words, assuming a situation in which a magnetic recording medium is written to a medium composed of a plurality of recording layers, in such a situation, when recording is performed on the lower recording layer, recording is also performed on the upper recording layer. As a result, it becomes impossible to selectively perform recording on the upper layer and the lower layer of the multilayer recording. That is, multilayer recording is a very difficult problem in principle in magnetic recording.

  Considering the situation of multi-level recording in addition to multi-layer recording, in the magnetic recording apparatus, the information of the recording bits of the medium identifies “1” and “0” upward and downward on the film surface. In order to overcome this state and perform multilevel recording, it is necessary to realize a state in which there is magnetization in the film surface, a state in which there is magnetization inclined 45 degrees from the film surface perpendicular, and the like. However, it is extremely difficult for such a tilted magnetization state and a magnetization state in the film surface to exist stably, and there is no concrete realization method at this stage. Under such circumstances, it is extremely difficult to realize multi-level recording in a magnetic recording apparatus.

  Based on this recognition, the present invention overcomes the limit of recording density improvement that has been relied only on the miniaturization of the bit size so far, and has achieved multilayer recording and multi-value recording in a magnetic recording apparatus that has not been realized so far. The object is to provide a solution to realize.

  The magnetic recording apparatus of the embodiment includes a magnetic storage medium including a plurality of recording layers each having a different magnetic resonance frequency, a magnetic recording head for writing information to the magnetic recording medium, and the magnetic recording medium from the magnetic recording medium A magnetic reproducing head for reading information. The magnetic recording head includes a high-frequency oscillation element that magnetically assists writing of the information to at least one of the recording layers, and the high-frequency oscillation element applies a high frequency to the at least one recording layer. When applied, the magnetization is selectively changed, and the high frequency is substantially equal to the magnetic resonance frequency of the at least one recording layer.

It is a figure which shows the magnetization state (recording state) of "0" and "1" in the magnetic recording medium of the conventional magnetic recording apparatus. It is a figure which shows the recording state in the magnetic recording medium of the magnetic recording device of embodiment. It is a figure which shows the recording state of each recording layer in the magnetic recording medium of the magnetic recording device of embodiment. It is a figure which shows schematic structure in an example of the magnetic recording medium of the magnetic recording device of embodiment. It is a figure which shows schematic structure in the other example of the magnetic recording medium of the magnetic recording device of embodiment. It is a figure which shows schematic structure in the other example of the magnetic recording medium of the magnetic recording device of embodiment. It is a figure which shows schematic structure in the further another example of the magnetic recording medium of the magnetic recording device of embodiment. It is explanatory drawing which shows roughly the recording system in the magnetic head in the magnetic recording device of embodiment. It is a figure which shows roughly the whole structure in an example of the magnetic head used with the magnetic recording device of embodiment. It is a figure which shows schematically the whole structure in the other example of the magnetic head used with the magnetic recording device of embodiment. It is a figure which shows schematically the whole structure in the other example of the magnetic head used with the magnetic recording device of embodiment. It is a figure which shows schematically the whole structure in the further another example of the magnetic head used with the magnetic recording device of embodiment. It is a block diagram which shows roughly an example of the high frequency oscillation element used with the magnetic recording device of embodiment. It is a block diagram which shows roughly the other example of the high frequency oscillation element used with the magnetic recording device of embodiment. It is a block diagram which shows roughly the other example of the high frequency oscillation element used with the magnetic recording device of embodiment. It is a block diagram which shows schematically the further another example of the high frequency oscillation element used with the magnetic recording device of embodiment. It is a block diagram which shows roughly the other example of the high frequency oscillation element used with the magnetic recording device of embodiment. It is a block diagram which shows roughly the other example of the high frequency oscillation element used with the magnetic recording device of embodiment. It is a figure which shows schematic structure of the magnetic recording / reproducing apparatus containing the magnetic head used by embodiment. It is a figure which shows schematic structure of the magnetic head assembly incorporated in the magnetic recording / reproducing apparatus shown in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Principle of multi-layer recording / multi-value recording)
First, the principle of multilayer recording / multi-value recording of the magnetic recording apparatus according to this embodiment will be described in comparison with the prior art.

<Playback>
FIG. 1 is a diagram showing magnetization states (recording states) of “0” and “1” in a magnetic recording medium of a conventional magnetic recording apparatus. As shown in FIG. 1, in the magnetic recording medium, values of “1” and “0” are recorded corresponding to the upward and downward bits of the magnetization surface. In this case, “1” can be recorded corresponding to the upward magnetization state of the film surface, and “0” can be recorded corresponding to the downward magnetization state of the film surface. It is also possible to record with “0” corresponding to the state, and with “1” corresponding to the magnetization state facing down the film surface.

  Here, each bit is not only a continuous film medium, but also a Discrete Track Media (Discrete Track Media: DTM) in which each track is divided by a non-magnetic material, as used in the current medium as standard. The principle is the same not only for each track but also for Bit Patterned Media (BPM) in which each bit is divided by a non-magnetic material.

  A magnetoresistive element is currently used for reproduction in which this state is detected by a magnetic head. A magnetoresistive element is an element that changes depending on the state of an external magnetic field depending on whether the resistance is high or low. The CIP-GMR (current-in-plane giantmagnetoresistive) has been widely used so far. Magnetoresistive elements using any of the principles, such as CMR-GMR (current-perpendicular-to-plane) film, which is a candidate for the future, as well as TMR (tunneling magnetoresistive) film that has recently been used, The principle that resistance is changed by an external magnetic field does not change. Therefore, as shown in the figure, it is possible to discriminate between “1” and “0” states by identifying the high resistance state and the low resistance state of the magnetoresistive effect element.

  FIG. 2 is a diagram showing a recording state on the magnetic recording medium of the magnetic recording apparatus of the present embodiment. As shown in FIG. 2, in order to realize the multi-valued recording state of the magnetic recording medium, even if the magnetization state of the magnetic recording medium is upward, the magnetization amount is strong and weak (left side in FIG. 2), Similarly, in the downward magnetization state, two states are realized: a strong state and a weak state (right side in FIG. 2). The realization of such a magnetized state (recorded state) will be described in detail below.

  When the remanent magnetization state of the magnetic recording medium has realized a state in which the strength is different in the perpendicular magnetization state, the state in which the external magnetic field is different can be realized as viewed from the magnetoresistive effect element. Then, there are multiple values of the magnetic field applied to the magnetoresistive effect element, and the resistance value of the magnetoresistive effect element changes according to each magnetic field. According to the plurality of resistance values of the magnetoresistive effect element, in the case of FIG. 2, four values of “0”, “1”, “2”, “3” can be identified.

  Such a four-value determination based on resistance is impossible when the resistance change amount of the magnetoresistive effect element is small. However, the resistance change amount of the magnetoresistive effect element, that is, an element having a large MR change ratio (magnetoresistance ratio). This is possible. For example, it can be realized by using a magnetoresistive effect element using a principle such as the above-described CIP-GMR film, TMR and CPP-GMR film. However, any film may be used as long as the resistance is largely changed by an external magnetic field. Furthermore, a magnetoresistive effect element using any principle may be used, such as a new principle MR element whose resistance changes according to a completely different principle.

  Changing the strength of the remanent magnetization state of the perpendicular magnetization state as shown in FIG. 2 cannot be realized only by the conventional medium structure. In order to realize such a magnetization state, a device is required on the medium side. The basic concept is shown in FIG.

  What is shown in FIG. 3A is a state in which the strength of the residual magnetization state differs for each bit. A concrete structure for realizing this is shown in FIG. 3B shown below. An important requirement is that the magnetic recording layer consisting of a hard film recorded as bits consists of multiple layers, and each magnetic recording layer is separated by a magnetic separation layer so that recording can be performed independently on each magnetic recording layer. It is that you are. The magnetic separation layer can be made of a material containing a nonmagnetic element. As an example, at least one element selected from the group consisting of Ru, Pd, Ir, and Pt can be included.

  Further explanation will be given using an example in which the magnetic recording layer is composed of two layers as shown in FIG. 3B. In the upper recording layer and the lower recording layer, the respective magnetizations are upward and downward. Therefore, a total of four states exist. At this time, if the magnetic film thickness Mrδ (Mr: residual magnetization, δ: film thickness of the magnetic recording layer) of the upper and lower magnetic recording layers is made the same, [magnetic recording layer upper layer: ↑] & [magnetic recording layer lower layer: The state of [↓] and the state of [Upper magnetic recording layer: ↓] & [Lower magnetic recording layer: ↑] are both zero when viewed from the top of the medium. There is no difference between the two states.

  Therefore, the [magnetic recording layer upper layer: ↑] & [magnetic recording layer lower layer: ↓] state and [magnetic recording layer upper layer: ↓] & [magnetic recording layer lower layer: ↑] state remain as viewed from above the medium. In order to make the magnetization states different, it is necessary to set Mrδ in the upper layer of the medium recording unit and Mrδ in the lower layer of the medium recording unit to be different. It does not matter which of the upper layer and the lower layer, Mrδ is increased. In the figure, the upper layer is thinner, the lower layer is thicker, and the upper layer Mrδ is set smaller and the lower layer Mrδ is set larger. By doing so, it becomes possible to realize a four-valued residual magnetization state as shown in the figure.

  Under such a basic concept, by using three or more magnetic recording layers, it is possible to realize eight values that are further multi-valued. FIG. 3 (c) shows a three-layer state. The magnetic recording layer is formed of three layers, and each layer is divided by a nonmagnetic magnetic separation layer. Furthermore, Mrδ of each layer is set to a different value. By doing so, it becomes possible to realize an eight-valued state as shown in FIG. Even when the octal value is reached, the reproduction method using the magnetoresistive effect element is exactly the same as in FIG. 2. The resistance value is divided into eight values, and the eight values are discriminated depending on which resistance value is indicated. This is possible with the playhead.

  In such a recording medium, the film forming the recording medium is a continuous medium formed two-dimensionally uniformly on the entire surface of the disk, a discrete track medium in which each track is divided by a nonmagnetic material, and each track. In addition, any bit patterned medium in which each bit is divided by a nonmagnetic material may be used. FIG. 4 shows the case of a continuous medium, FIG. 5 shows the case of a Discrete Track medium, and FIG. 6 shows the case of a Bit Patterned medium.

  In the case of a continuous film medium, the recording layer is uniformly formed over almost the entire surface of the disk as the medium film, and the place that functions as a bit is determined by whether or not it is recorded by the recording head and functions as a recording bit. The parts not to be formed are made of the same material. Here, the portions that do not function as recording bits are not shown in the figure, but between the tracks and between the bits of the same track are also formed of the same material as the recorded bit portion. On the other hand, in the case of Discrete media, each track is separated by a non-magnetic material (the non-magnetic material is not shown), and in the case of Bit Patterned media, not only between each track, The bit of the same track is also divided by a nonmagnetic material (the nonmagnetic material is not shown). From the reproduction principle, any of the above-described medium structures may be used, but from the recording principle, there may be a merit depending on each of the medium structures. This will be described later.

  Further, in the figure, only the magnetic recording layer and the magnetic separation layer that magnetically divides each recording layer are shown, but it goes without saying that a protective film or lubricant (lubricant) is formed on the uppermost magnetic recording layer. ) Is formed. Further, on the lower layer side of the lowermost magnetic recording layer, a backing magnetic layer and the like necessary for perpendicular magnetic recording are formed via a nonmagnetic underlayer. An example showing the medium structure on the lower layer side than the magnetic recording layer is shown in FIG.

  In the example shown in FIG. 7, the magnetic recording layers 1, 2, and 3 are laminated with each other via the magnetic separation layers 4 and 5, and the magnetic recording layer 3 has a lower layer for crystal control of the magnetic recording layer. A recording layer base layer 6 is formed. As the underlayer 6, it is desirable to use a nonmagnetic material in order to magnetically divide from the underlying magnetic layer 7 located in the lower layer. A backing magnetic layer 7 is used as a lower layer of the recording layer underlayer 6. The backing magnetic layer 7 is a layer that assumes the function of the other magnetic pole when the recording head is used as one magnetic pole in perpendicular magnetic recording, and a soft magnetic material is used. Further, an underlying layer 8 for the backing magnetic layer for controlling the crystallinity of the backing magnetic layer 7 is used under the backing magnetic layer 7. In the lower layer, a glass substrate, an aluminum substrate or the like is used as a medium substrate (not shown).

<Record>
Next, a method for realizing the multi-value recording state as shown in the drawing with the recording head will be described. The state as shown in FIG. 3 cannot be realized as long as a conventional recording head is used. When a magnetic field is applied by a conventional recording head, the direction of the magnetic field applied to all the layers is the same, so that recording can be performed only in the same direction for all the recording medium layers having a multilayer structure. Specifically, when a recording medium layer having a two-layer structure as shown in FIG. 3B is used, even if recording is performed on the lower magnetic recording layer, a magnetic field is applied to the upper recording medium layer in the same direction. Therefore, a magnetic field is always applied to the upper layer in the same direction as the lower layer, and the magnetization is fixed. In this case, the meaning of the substantial multilayer structure disappears, and it is impossible to perform multi-value recording as shown in FIG.

  Therefore, FIG. 8 shows specific realization means. In the magnetic recording head shown in FIG. 8, high-frequency assist recording is performed using a high-frequency oscillation element having a variable oscillation frequency in addition to the recording magnetic pole. In this case, it is possible to selectively record on each magnetic recording layer regardless of the vertical position of the magnetic recording layer. The principle will be described below.

First, the principle of high-frequency assist recording, which is a known technique, will be described. The high frequency assisted recording is Jian-Gang Zhu et al, CMU, B6 “Microwave Assisted Magnetic Recording for 1 Terabit / in ² Density and Beyond”, The 18 ^th International Conference on Magnetic Recording Heads and Systems, May 21-23, 2007, Minneapolis , MN, USA, by applying a direct current perpendicular to the film surface to a laminated film consisting of at least a magnetic layer / non-magnetic layer / magnetic layer using a spin torque effect, the high frequency Oscillation is generated, and the high frequency is used as an energy assist source to reduce the magnetic field to be written on the recording medium. By using a value close to the magnetic resonance frequency of the recording medium as the frequency of the high-frequency assist magnetic field, the assist effect for reducing the reversal magnetic field is increased, and the magnitude of the external magnetic field required for reversal can be reduced. .

  The inventors have found that multi-value recording can be realized by adding the following device to high-frequency assist recording for the purpose of reducing the writing magnetic field. First, in a medium composed of a plurality of recording layers which is a precondition for multilevel recording as shown in FIG. 3, the magnetic resonance frequency of each magnetic recording layer is set to be changed. By doing so, the energy assist effect by the high frequency signal can be obtained only for a specific medium with respect to the high frequency magnetic field generated from the high frequency oscillation element of the recording head, and the other medium has no energy assist effect. .

  In the present embodiment, as shown in FIG. 8, a high-frequency oscillation element is disposed in the vicinity of the recording magnetic pole. Almost simultaneously with the generation of the write magnetic field from the recording magnetic pole, a high frequency assist magnetic field having a specific frequency is generated from the high frequency oscillation element. Then, in a medium composed of a plurality of recording layers, an assist effect by a high frequency signal can be obtained only for a specific recording layer. More specifically, an energy assist effect is obtained by oscillating a high-frequency signal substantially equal to the magnetic resonance frequency of a specific magnetic recording layer from the recording head, and the magnitude of the magnetic field from the recording magnetic pole is only the magnetic field. Even a value smaller than the magnetic field required for writing can be written to the magnetic recording layer.

  Here, if the materials of a plurality of recording layers are the same, an assist effect by a high-frequency signal is obtained in any recording layer, and it becomes impossible to perform recording only on a specific layer. In the present embodiment related to FIG. 8, by irradiating a high frequency assist magnetic field f2 in the vicinity of the magnetic resonance frequency f2 ′ of the magnetic recording layer 2, an energy assist effect is given only to the magnetic recording layer 2 and at the same time a write magnetic field. Writing (magnetization reversal) can be performed with H. This write magnetic field H is not sufficient to reverse the magnetization of the magnetic recording layers 1 to 3 with such a magnetic field, so that no magnetization reversal occurs in the magnetic recording layers 1 and 3.

  The writing to the magnetic recording layers 1 and 3 can be performed in the same manner as the magnetic recording layer 2. When writing the magnetic recording layer 1, a high frequency magnetic field f1 corresponding to the ferromagnetic resonance frequency f1 'of the magnetic recording layer 1 is oscillated from the high frequency oscillation element, and a writing magnetic field H is applied from the recording magnetic pole. When writing to the magnetic recording layer 3, a high frequency magnetic field f3 'corresponding to the ferromagnetic resonance frequency f3' of the magnetic recording layer 3 is oscillated from the high frequency oscillation element, and a writing magnetic field H is applied from the recording magnetic pole.

  Here, the most straightforward design philosophy is to set the high frequency magnetic fields f1 to f3 to values substantially equal to the corresponding ferromagnetic resonance frequencies f1 'to f3'. By doing so, energy from the high-frequency signal can be efficiently applied to the medium layer, and ferromagnetic resonance can be generated. However, if the high frequency magnetic fields f1 to f3 are set within a range of ± 1 GHz or less with respect to the corresponding ferromagnetic resonance frequencies f1 ′ to f3 ′, the recording operation using the ferromagnetic resonance as described above is performed. Is possible.

  Further, even if the high frequency magnetic fields f1 to f3 and the ferromagnetic resonance frequencies f1 'to f3' are not equal values, it is possible to produce an energy assist effect. Specifically, the frequency is (1/2) × f1 ′ times the ferromagnetic resonance frequency f1 ′, or an integer multiple of (1/2) × f1 ′ such as n × (1/2) × f1 ′. An energy assist effect can also be obtained by applying a high frequency. The same applies to f2 and f3.

  Here, in order to change the magnetic resonance frequency (the above-described ferromagnetic resonance frequency) of each magnetic recording layer, that is, the switching magnetic field, it is most efficient to change the material of the magnetic recording layer. As is well known, it is known that the magnetic resonance frequency of a magnetic material increases as the anisotropic magnetic field of the magnetic material increases.

  As can be seen from this equation, in order to change the magnetic resonance frequency, it is necessary to change the magnetic anisotropy energy of the ferromagnetic material. The magnetic anisotropy energy can be changed by, for example, stacking another ferromagnetic layer to be stacked on the magnetic recording layer, or the type and concentration of the additive element added to the ferromagnetic material.

  The magnetic resonance frequencies of the plurality of recording layers are preferably different by at least 1 GHz. Thereby, for example, selective recording on the magnetic recording layer using the above-described difference in magnetic resonance frequency can be easily performed.

  Further, in order to have each of the plurality of recording layers as described above have magnetic resonance frequencies different from each other by 1 GHz or more, the plurality of recording layers are made of a group consisting of Co, Fe, Ni, and Pt. It is preferable that at least one element selected is included, and the content of the element is different from each other by 5 atomic% or more in each of the plurality of recording layers.

  Further, as can be seen from the above principle, an important function required as a high-frequency oscillation element is that the oscillation frequency can be arbitrarily changed. As for the variable frequency range, it is important that when a high-frequency oscillation element with a specific frequency is applied to the medium, only a specific medium causes ferromagnetic resonance and no other magnetic recording layer causes ferromagnetic resonance. It is. Specifically, it is preferable that the oscillation frequency be variable on the order of 1 GHz or more. A specific example of such a high-frequency oscillation element will be described later.

<Magnetic recording medium>
The type of magnetic recording medium that performs the above-described multi-layer recording / multi-value recording is not particularly limited as long as it has a plurality of recording layers so as to exhibit different amounts of magnetization according to recording of different information as the whole medium. For example, a continuous film medium in which the recording layer is uniformly formed on almost the entire surface of the disk can be used. However, not only the discrete track medium in which each track is divided by a nonmagnetic material, but also each track. It is preferable to use a Bit Patterned medium in which each bit is divided by a nonmagnetic material.

  When a high frequency magnetic field is applied to such Discrete Track media and Bit Patterned media, the periphery is divided by a non-magnetic material, so that magnetic resonance can be efficiently concentrated only on the recording bit part. There is a case. In these media, the recording part is made of a metal layer, and the bits between the non-recording parts are made of an insulating layer. Therefore, a high-frequency magnetic field is efficiently applied to the metal layer, which is the recording part, and high-frequency energy is efficiently recorded. This is because it can be applied to the bit portion. Note that the forms of the continuous film medium, the discrete track medium, and the bit patterned medium are as shown in FIGS.

(Overall structure of magnetic head)
Next, the overall structure of the magnetic head used in the magnetic recording apparatus of this embodiment will be described. 9 to 12 schematically show the configuration of the magnetic head.

  In the magnetic head shown in FIG. 9, a reproducing unit 10 configured to sandwich the magnetoresistive effect element 11 between an upper shield 12 and a lower shield 13, a recording magnetic pole 21, and a yoke 22 to which the rear end of the recording magnetic pole 21 is connected, In addition, the recording unit is configured to include a coil 23 that winds the recording magnetic pole 21 and generates a predetermined recording magnetic field with respect to the recording magnetic pole 21, and a high-frequency oscillation element 25 that is disposed between the recording magnetic pole 21 and the yoke 22. 20 and so on. The reproducing unit 10 and the recording unit 20 are located adjacent to each other.

  The magnetic head shown in FIG. 10 differs from the magnetic head shown in FIG. 9 in that the high-frequency oscillation element 25 is arranged outside the recording magnetic pole 21 in the recording unit 20, and is the same in other points. In the magnetic head shown in FIG. 11, the upper shield 12 of the reproducing unit 10 also serves as the yoke 22 of the recording unit 20, and the other configuration is the same as that of the magnetic head shown in FIG. In the magnetic head shown in FIG. 12, the magnetoresistive effect element 11 in the reproducing unit 10 also serves as the high-frequency oscillation element 25 in the recording unit 20.

  As will be described later, since the magnetoresistive effect element and the high-frequency oscillation element have substantially the same film configuration, the magnetoresistive effect element 11 can also be used as the high-frequency oscillation element 25 as shown in FIG. As a result, the time required for manufacturing the magnetic head can be greatly reduced, and the yield can be improved. In this case, the magnetoresistive effect element 11 is energized with a predetermined drive current so as to exhibit the original reproducing element function during reproduction, but functions as a high-frequency oscillation element serving as a high-frequency assist source during recording. Therefore, a predetermined drive current is energized. In this case, the current value to be energized at the time of reproduction is different from that at the time of recording, and when it is used as a high-frequency oscillation element at the time of recording, a design that requires a larger current value.

  In addition, the magnetic head of any other configuration can be used as long as it can perform the above-described multi-layer recording / multi-value recording and reproduction without being limited to the above embodiment.

(High frequency generator)
Next, the high-frequency oscillation element used in the magnetic recording apparatus of this embodiment will be specifically described. FIG. 13 is a schematic configuration diagram illustrating an example of the high-frequency oscillation element.

  In the high-frequency oscillation device 25 shown in FIG. 13, between the lower electrode 251 and the upper electrode 260, the base layer 252, the pinning layer 253, the first pinned layer 254, the magnetic coupling layer 255, the second pinned layer 256, the spacer layer 257, The free layer 258 and the cap layer 259 are sequentially stacked. The pinning layer 253 to the free layer 258 constitute a vertical energization type spin valve structure, and the lower electrode 251 and the upper electrode 260 are electrodes for energizing the spin valve structure in the stacking direction (vertical direction). It is composed.

  The first pinned layer 254 is pinned by a pinning layer 253, and the second pinned layer 256 is antiferromagnetically coupled to the first pinned layer 254 via the magnetic coupling layer 255, so-called synthetic antiferro ( (Or synthetic anti-ferri) structure.

  In the high-frequency oscillation element 25 shown in FIG. 13, the three-layer structure of the second pinned layer 256, the spacer layer 257, and the free layer 258 generates high-frequency oscillation by the above-described spin torque effect by energization, and the high frequency is generated as an energy assist source. As described above, the magnetic field for writing to the recording medium is reduced.

  For the lower electrode 251 and the upper electrode 260, NiFe, Cu or the like having a relatively low electric resistance can be used.

  The underlayer 252 can be divided into, for example, a buffer layer and a seed layer. The buffer layer is a layer for reducing the roughness of the surface of the lower electrode 251. The seed layer is a layer for controlling the crystal orientation and crystal grain size of the spin valve film formed thereon. As the buffer layer, Ta, Ti, W, Zr, Hf, Cr or an alloy thereof can be used, and the thickness is about 2 to 10 nm, preferably about 3 to 5 nm. The seed layer has an fcc structure (face-centered cubic structure), an hcp structure (hexagonal close-packed structure), or a bcc structure (body-centered cubic structure: body-centered cubic structure). A metal layer such as Ru, NiFe or the like is preferable. The thickness of the seed layer can be, for example, 1 to 5 nm, preferably 5 to 3 nm.

  The pinning layer 253 has a function of fixing magnetization by imparting unidirectional anisotropy to the first pinned layer 254 formed thereon. As a material for the pinning layer 253, an antiferromagnetic material such as PtMn, PdPtMn, IrMn, or RuRhMn can be used. Further, the optimum thickness varies depending on the material, but is on the order of several nm to several tens of nm, for example.

The first pinned layer 254 and the second pinned layer 256 are made of a ferromagnetic material such as CoFe or NiFe. The magnetic coupling layer 255 is made of a non-ferromagnetic material such as Ru or Cu. The first pinned layer 254, the magnetic coupling layer 255, and the second pinned layer 256 are, for example, Co ₉₀ Fe ₁₀ 3.5 nm / Ru / (Fe ₅₀ Co ₅₀ [1 nm] / Cu [0.25 nm]) × 2 / Fe _50. Co ₅₀ [1 nm]).

The spacer layer 257 is made of oxide, nitride, oxynitride, or the like. For example, there may be both an amorphous structure such as Al ₂ O ₃ and a crystal structure such as MgO. In order to exhibit a function as a spacer layer, 1 to 3.5 nm is preferable, and a range of 1.5 to 3 nm is more preferable. Further, Ti, Hf, Mg, Zr, V, Mo, Si, Cr, Nb, Ta, W, B, C, V, and the like can be added as additive elements. The addition amount of these additive elements can be appropriately changed within a range of about 0% to 50%. As an example, about 2 nm of Al ₂ O ₃ can be used as the spacer layer 257.

For the spacer layer 257, instead of Al oxide such as Al ₂ O ₃ , Ti oxide, Hf oxide, Mg oxide, Zr oxide, Cr oxide, Ta oxide, Nb oxide, Mo oxidation Materials, Si oxides, V oxides, and the like can also be used. Even in the case of these oxides, the above-described materials can be used as additive elements. Further, the amount of the additive element can be appropriately changed within a range of about 0% to 50%.

The free layer 258 expresses a spin torque effect. For example, the free layer 258 has a two-layer structure of Co ₉₀ Fe ₁₀ [1 nm] / Ni ₈₃ Fe ₁₇ [3.5 nm] using NiFe by inserting CoFe into the interface. Can be mentioned. In this case, it is preferable to provide a CoFe alloy at the interface with the spacer layer 257 rather than a NiFe alloy. Moreover, as the free layer 258, a CoFe layer or Fe layer having a thickness of 1 to 2 nm and an ultrathin Cu layer having a thickness of about 0.1 to 0.8 nm may be alternately stacked.

  The cap layer 259 has a function of protecting the spin valve film. The cap layer 259 can have, for example, a plurality of metal layers, for example, a two-layer structure (Cu [1 nm] / Ru [10 nm]) of a Cu layer and a Ru layer. As the cap layer 259, a Ru / Cu layer in which Ru is disposed on the free layer 258 side or the like can also be used. In this case, the film thickness of Ru is preferably about 0.5 to 2 nm. The cap layer 259 having this configuration is particularly desirable when the free layer 258 is made of NiFe. This is because Ru has a non-solid relationship with Ni, so that magnetostriction of the interface mixing layer formed between the free layer 258 and the cap layer 259 can be reduced.

  FIG. 14 is a schematic configuration diagram showing another example of the high-frequency oscillation element used in the magnetic recording apparatus of the present embodiment. In the high-frequency oscillation element 25 shown in FIG. 14, the spacer 257 has an insulating layer 257A and a current path 257B, and further has a lower metal layer 257C and an upper metal layer 257D, compared to the high-frequency oscillation element 25 shown in FIG. In other respects, the other configurations are the same. Therefore, in the following, only the spacer 258 will be described in detail, and description of other components will be omitted.

The insulating layer 257A is made of oxide, nitride, oxynitride, or the like. The insulating layer 257A can have both an amorphous structure such as Al ₂ O ₃ and a crystal structure such as MgO. In order to exhibit the function as the spacer layer, the thickness is preferably 1 to 3.5 nm, and more preferably 1.5 to 3 nm.

As a typical insulating material used for the insulating layer 257A, there are a material using Al ₂ O ₃ as a base material and a material obtained by adding an additive element thereto. Examples of additive elements include Ti, Hf, Mg, Zr, V, Mo, Si, Cr, Nb, Ta, W, B, C, and V. The addition amount of these additive elements can be appropriately changed within a range of about 0% to 50%. As an example, about 2 nm of Al ₂ O ₃ can be used as the insulating layer 257A. Also, instead of Al oxide such as Al ₂ O ₃ , Ti oxide, Hf oxide, Mg oxide, Zr oxide, Cr oxide, Ta oxide, Nb oxide, Mo oxide, Si oxide A material, V oxide, or the like can also be used. Even in the case of these oxides, the above-described materials can be used as additive elements. Further, the amount of the additive element can be appropriately changed within a range of about 0% to 50%.

  The current path 257B is a path (path) through which a current flows perpendicularly to the film surface of the spacer layer 257, and is for constricting the current. It functions as a conductor that allows current to pass in the direction perpendicular to the film surface of the insulating layer 257A, and can be composed of, for example, a metal layer such as Cu. In other words, the spacer layer 257 has a current confinement structure (CCP structure) and can increase the spin torque effect by the current confinement effect. Examples of the material forming the current path 257B (CCP) include Au, Ag, Al, Ni, Co, Fe, or an alloy layer including at least one of these elements, in addition to Cu. The diameter of the current path 257B is on the order of several nm, specifically, 1 nm or more and 10 nm or less.

The upper metal layer 257D forms part of a broader spacer layer. The free layer 258 formed thereon has a function as a barrier layer for protecting the spacer layer 257 from being oxidized in contact with the oxide of the spacer layer 257 and a function for improving the crystallinity of the free layer 258. For example, when the material of the insulating layer 257A is amorphous (for example, Al ₂ O ₃ ), the crystallinity of the metal layer formed thereon is deteriorated, but the layer that improves the fcc crystallinity (for example, By arranging the (Cu layer) (the film thickness may be about 1 nm or less), the crystallinity of the free layer 258 can be remarkably improved.

  Note that the upper metal layer 257D is not necessarily provided. In addition, the lower metal layer 257C is a layer that is a base for producing the current path 257B, and is made of the same material as the current path 257B.

In the high-frequency oscillation element 25 having the configuration shown in FIG. 14, for example, as disclosed in Japanese Patent Application Laid-Open No. 2007-124340, the current density in the current path 257B exceeds 10 ⁸ A / cm ² due to the current confinement effect. This is because an effect is likely to occur. That is, the current path 257B functions as a trigger for the spin transfer effect. When such a spin transfer effect occurs, high-frequency oscillation can be executed more easily. That is, not only the positioning as a high-frequency oscillation element for multi-value recording and multi-layer recording but also a case where such a current path 257B, that is, an element having a nano-current path structure is suitable for a use as a high-frequency oscillation element for high-frequency assist recording. There is.

  FIG. 15 is a modification of the high-frequency oscillation element 25 shown in FIG. In the example shown in FIG. 14, the spacer layer having the nano-current path structure is provided as a single layer. However, in the high-frequency oscillation element 25 shown in FIG. 15, two spacer layers having the nano-current path structure are provided. Specifically, a third pinned layer 262 is newly provided, and a pair (two layers) of spacer layers 257 are provided so as to sandwich the third pinned layer 262. In the high-frequency oscillator 25 shown in FIG. 15, since the spacer layer 257 having a two-layer nanocurrent path structure is provided, the current confinement effect is further increased and the above-described spin transfer effect is likely to occur. Therefore, high-frequency oscillation can be performed more easily.

  In the high frequency oscillation element 25 shown in FIG. 15, the specific configuration of the spacer layer 257 has the same configuration as that of the high frequency oscillation element 25 shown in FIG. Other configurations except the spacer layer 257 are the same as those of the high-frequency oscillation element 25 shown in FIG.

  The number of spacer layers is not limited to the single layer and the two layers as described above, and may be three or more.

  FIG. 16 is a schematic configuration diagram showing another example of the high-frequency oscillation element used in the magnetic recording apparatus of the present embodiment. In the high-frequency oscillation element 25 shown in FIG. 16, compared with the high-frequency oscillation element 25 shown in FIG. 13, an insulating layer is formed between the lower electrode 251 and the upper electrode 260 on the side surface of the laminated structure of the base layer 252 to the cap layer 259. The difference is that the hard bias layer 264 is formed via the H.263, and the other configurations are the same.

  In the case of a high frequency oscillation element, in order to oscillate a high frequency, it is necessary to increase the magnetic anisotropy of the layer to be a free layer. That is, it is necessary to use the magnetic layer in a magnetically hard state, that is, in a state where a magnetic field bias is applied. Therefore, as shown in FIG. 16, by forming a hard bias layer 264 through an insulating layer 263 on the side surface of the laminated structure of the base layer 252 to the cap layer 259, the free layer 258 is magnetically hard and magnetized. It can be made difficult to rotate.

  In the case of a magnetoresistive effect element, the hard bias layer does not apply a very strong bias magnetization because the primary purpose is to direct the magnetic domain of the free layer in a single direction. Applies a relatively strong bias magnetization to magnetically harden the free layer 258 as described above. This is used for the same purpose as that disclosed in Japanese Patent Application Laid-Open No. 2007-124340.

  The hard bias layer 264 can be made of, for example, CoPt, CoCrPt, CoCr, and FePt.

  FIG. 17 is a schematic configuration diagram showing still another example of the high-frequency oscillation element used in the magnetic recording apparatus of the present embodiment. The high-frequency oscillation element 25 shown in FIG. 17 is different in that a pair of current wirings 265 are provided on the side surface side of the laminated structure of the high-frequency oscillation element 25 shown in FIG. 13, and the other configurations are the same.

  In the high-frequency oscillation element 25 configured as shown in FIG. 17, the magnetic field strength applied to the free layer 258 can be controlled using the current magnetic field from the pair of current wires 265. This is used for the same purpose as that disclosed in Japanese Patent Application Laid-Open No. 2007-124340. Therefore, by adjusting the intensity of the magnetic field to be applied by appropriately controlling the magnitude of the current magnetic field, the frequency of the oscillation high frequency can be easily increased to the order of several tens of GHz.

  FIG. 18 shows a modification of the high-frequency oscillation device shown in FIG. In the high-frequency oscillation element 25 shown in FIG. 16, the pair of current wirings 265 are provided on the side surface side of the laminated structure of the high-frequency oscillation element 25, but in the high-frequency oscillation element 25 shown in FIG. It is provided above the laminated structure (upper electrode 260). Even in this case, the magnetic field strength applied to the free layer 258 can be controlled using the current magnetic field from the current wiring 266, and the magnetic field strength applied by appropriately controlling the magnitude of the current magnetic field. By adjusting, the frequency of the oscillation high frequency can be easily increased to the order of several tens of GHz.

  Although not particularly illustrated, the current wiring can be provided below the laminated structure (lower electrode 251) of the high-frequency oscillation element 25, or a pair of current wirings can be provided above and below the laminated structure. it can.

(Magnetoresistive element)
Next, the magnetoresistive effect element used in the magnetic recording apparatus of this embodiment will be described. As described above, as the magnetoresistive effect element, a magnetoresistive effect element using a principle such as a CIP-GMR film, a TMR film, and a CPP-GMR film can be used.

  The magnetoresistive effect element using the CPP-GMR film adopts the configuration shown in FIGS. 13 to 15 described in the high-frequency oscillation element. Further, the characteristics required for each component (each layer) are the same as those of the high-frequency oscillation element. However, the three-layer structure of the second pinned layer 256, the spacer layer 257, and the free layer 258 functions as a so-called magnetoresistive effect film, exhibits a magnetoresistive effect instead of causing high-frequency oscillation by the spin torque effect, and performs magnetic recording. It functions to detect the intensity of the magnetic field from the medium, detect the magnitude of the magnetization, and read the written information.

  Also, the magnetoresistive effect element can be provided with a hard bias layer on the side surface of the basic laminated structure, similarly to the high-frequency oscillation element shown in FIG. In this case, since the hard bias layer has a primary purpose of directing the magnetic domain of the free layer in a single direction, the hard layer is different from the hard bias layer of the high-frequency oscillation element in order to make the free layer 258 magnetically hard. Apply relatively weak bias magnetization.

  Note that magnetoresistive elements using the principles of the CIP-GMR film and the TMR film are already widely used, and can be appropriately selected from these. For example, the configuration of the magnetoresistive effect element using the principle of the TMR film can be obtained by configuring the spacer layer 257 with an insulating film such as MgO in the high-frequency oscillation element configured as shown in FIG.

(Hard disk and head gimbal assembly)
9 to 12 can be incorporated in a recording / reproducing integrated magnetic head assembly (HGA) and mounted on a magnetic recording / reproducing apparatus. FIG. 20 is a diagram showing a schematic configuration of a magnetic head assembly incorporated in the magnetic recording / reproducing apparatus shown in FIG.

  The magnetic recording / reproducing apparatus 300 of this embodiment is an apparatus using a rotary actuator. In the figure, a magnetic disk 370 is mounted on a spindle 310 and is rotated in the direction of arrow A by a motor (not shown) that responds to a control signal from a drive device control unit (not shown). The magnetic recording / reproducing apparatus 300 of this embodiment may include a plurality of magnetic disks 370.

  A head slider 320 for recording / reproducing information stored in the magnetic disk 370 is attached to the tip of a thin film suspension 330. The head slider 320 has a magnetic head including the magnetoresistive effect element according to any one of the above-described embodiments mounted near its tip.

  When the magnetic disk 370 rotates, the medium facing surface (ABS) of the head slider 320 is held with a predetermined flying height from the surface of the magnetic disk 370. Alternatively, a so-called “contact traveling type” in which the slider contacts the magnetic disk 370 may be used.

  The suspension 330 is connected to one end of the actuator arm 340. A voice coil motor 350, which is a kind of linear motor, is provided at the other end of the actuator arm 340. The voice coil motor 350 includes a drive coil (not shown) wound around a bobbin portion, and a magnetic circuit including a permanent magnet and a counter yoke arranged so as to sandwich the coil.

  The actuator arm 340 is held by ball bearings (not shown) provided at two positions above and below the spindle 360, and can be freely rotated and slid by a voice coil motor 350.

  A magnetic head assembly 400 shown in FIG. 20 shows a state where the head gimbal assembly ahead of the actuator arm 340 is viewed from the disk side. The magnetic head assembly 400 includes the actuator arm 340, and a suspension 330 is provided at one end of the actuator arm 340. Is connected. A head slider 320 including the magnetic head according to any one of the above-described embodiments is attached to the tip of the suspension 330. The suspension 330 has a lead wire 410 for writing and reading signals, and the lead wire 410 and each electrode of the magnetic head incorporated in the head slider 320 are electrically connected. In the figure, 420 is an electrode pad of the assembly 400.

  According to the magnetic recording / reproducing apparatus and magnetic head assembly of the present embodiment, the magnetic head including the above-described high-frequency oscillation element is provided. Can be realized.

  As mentioned above, although several embodiment of this invention was described, these embodiment was posted as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

1, 2, 3 Magnetic recording layers 4, 5 Magnetic separation layer 6 Recording underlayer 7 Backing magnetic layer 8 Backing layer underlayer 10 Reproducing portion 11 Magnetoresistive element 12 Upper shield 13 Lower shield 20 Recording portion 21 Recording magnetic pole 22 Yoke 23 Coil 25 High frequency oscillation element

Claims (18)

A magnetic storage medium comprising a plurality of recording layers each having a different magnetic resonance frequency;
A magnetic recording head for writing information to the magnetic recording medium;
A magnetic reproducing head for reading the information from the magnetic recording medium,
The magnetic recording head includes a high-frequency oscillation element that magnetically assists writing of the information to at least one of the recording layers,
The high-frequency oscillation element is configured to selectively change its magnetization by applying a high frequency to the at least one recording layer,
The magnetic recording apparatus according to claim 1, wherein the high frequency is substantially equal to a magnetic resonance frequency of the at least one recording layer.   The magnetic reproducing head detects a magnetic field strength caused by a total magnetization amount of the plurality of recording layers in the magnetic recording medium, and based on the detected magnetic field strength, the information recorded on the magnetic recording medium is recorded. The magnetic recording apparatus according to claim 1, wherein reading is performed.   2. The magnetic recording apparatus according to claim 1, wherein magnetic resonance frequencies of the plurality of recording layers are different from each other by at least 1 GHz.   The plurality of recording layers each include at least one element selected from the group consisting of Co, Fe, Ni, and Pt, and the contents of the elements are different from each other by 5 atomic% or more in each of the plurality of recording layers. The magnetic recording apparatus according to claim 1.   The magnetic recording apparatus according to claim 1, wherein each of the plurality of recording layers is magnetically separated by a magnetic separation layer containing a nonmagnetic element.   The magnetic memory device according to claim 5, wherein the magnetic separation layer includes at least one element selected from the group consisting of Ru, Pd, Ir, and Pt.   The magnetic recording apparatus according to claim 1, wherein each track of the magnetic storage medium is separated by a nonmagnetic material.   2. The magnetic recording apparatus according to claim 1, wherein the oscillation frequency of the high-frequency oscillation element is set within a range of ± 1 GHz or less with respect to a magnetic resonance frequency of the at least one recording layer.   When the oscillation frequency of the high-frequency oscillation element is f and the magnetic resonance frequency of the at least one recording layer is f ′, the relationship f = n × f ′ / 2 (n: integer) is satisfied. The magnetic recording apparatus according to claim 1, wherein the magnetic recording apparatus is characterized in that:   The magnetic recording apparatus according to claim 1, wherein the high-frequency oscillation element can vary the oscillation frequency on the order of 1 GHz or more.   The high-frequency oscillation element includes a laminated structure including at least a magnetization fixed layer, a spacer layer, and a free layer, and a pair of electrodes formed at both ends of the laminated structure and energized in a direction perpendicular to the film surface. The magnetic recording apparatus according to claim 1, wherein:   The spacer layer has an insulating layer and a plurality of metal layers penetrating the insulating layer in the thickness direction, and the metal layer functions as a metal path for passing a current between the magnetization pinned layer and the free layer. The magnetic recording apparatus according to claim 11, wherein:   The insulating layer includes at least one selected from the group consisting of Al, Ti, Hf, Mg, Zr, V, Mo, Si, Cr, Nb, Ta, W, B, C, and V, and the plurality of metal layers The magnetic storage device according to claim 12, comprising: at least one selected from the group consisting of Cu, Au, Ag, Al, Fe, Co, and Ni.   The magnetic recording apparatus according to claim 12, wherein each of the plurality of metal layers has a diameter of 1 nm to 10 nm.   The magnetic recording apparatus according to claim 10, wherein the high-frequency oscillation element is interposed between two hard magnetic layers.   The magnetic recording apparatus according to claim 10, wherein the high-frequency oscillation element includes a free layer and a current wiring for applying a current magnetic field to the free layer.   The magnetic recording apparatus according to claim 1, wherein the high-frequency oscillation element functions as a magnetoresistive effect element in the magnetic reproducing head.   18. The high-frequency oscillation element is characterized in that a current value to be energized when used as the magnetoresistive effect element is smaller than a current value to be energized when used as an original high-frequency oscillation element. The magnetic recording apparatus described in 1.

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