JP2006277807A - Magnetoresistance effect element and magnetic head equipped with this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetoresistance effect element which is increased in magnetic resistance change by satisfying both of increase in spin dependent interface scattering and increase in spin dependent bulk scattering. <P>SOLUTION: A magnetoresistance effect element (10) is equipped with a magnetoresistance effect film (13), and an upper electrode and a lower electrode impressing sense current in the direction perpendicular to the above magnetoresistance effect film. The magnetoresistance effect film includes; a 1st magnetic layer (20) from which the magnetization direction changes with external magnetic fields; a 2nd magnetic layer (16) to which the direction of magnetization is fixed to the above external magnetic field; and a non-magnetic intermediate layer (18) which separates magnetically the above 1st magnetic layer and a 2nd magnetic layer. At least one of the 1st and 2nd magnetic layers consists of ferromagnetic materials to which impurity elements are added, and the addition of the impurity elements are set so that it may become high bulk side in layer and may rather than the interface side to the non-magnetic intermediate layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetoresistive effect element, and more particularly, to a magnetoresistive effect element having a CPP (Current Perpendicular to Plane) structure using a so-called spin valve film and causing a sense current to flow in the film thickness direction, and such a magnetoresistive effect element. The present invention relates to a magnetic head provided.

  In recent years, a giant magnetoresistive (GMR) effect element having a multilayer structure film in which a nonmagnetic metal layer such as Cu is sandwiched between two ferromagnetic layers has been developed. GMR uses spin-dependent scattering in a ferromagnetic layer or at an interface. That is, when the magnetization directions of the two magnetic layers are aligned, conduction electrons having a spin in a certain direction are difficult to be scattered and the resistance is low, but when the magnetization directions are antiparallel, the conduction electrons are easily scattered and the resistance is reduced. It takes advantage of the property that becomes higher.

  In a magnetoresistive effect element using a spin valve film having a multilayer structure, an antiferromagnetic material is brought close to one of the two ferromagnetic layers to fix the spin direction (pinned layer), The other magnetic layer is configured such that the magnetization direction easily changes with respect to an external magnetic field (free layer). The direction and magnitude of the external magnetic field can be detected based on the change in the element resistance by utilizing the property that the element resistance changes depending on the relative angle of the magnetization direction between the two magnetic layers.

  Such a magnetoresistive effect element is applied to a magnetic sensor, a reproducing head of a hard disk drive, and the like and put into practical use.

  In a conventional magnetoresistive effect element using a spin valve film, a magnetoresistive effect of a CIP (Current In Plane) structure that detects a change in resistance in the film surface direction by flowing a sense current in the film surface direction of the spin valve film. Devices are known.

  On the other hand, a magnetoresistive effect of a CPP (Current Perpendicular to Plane) structure that senses a change in resistance in the film thickness direction by passing a sense current in the film thickness direction of the spin valve film as a magnetoresistive effect element with higher density and higher sensitivity. The device is drawing attention. A magnetoresistive effect element having a CPP structure has a feature that the element output increases as the size decreases, and is promising as a highly sensitive reproducing head in a high-density magnetic recording apparatus.

  Unlike a CIP structure, a spin valve element with a CPP structure passes a sense current through each film surface, so in addition to the spin-dependent interface scattering resistance at the magnetic / nonmagnetic interface, which was the main cause of the resistance change of the CIP structure element. By selecting a magnetic material having a large spin-dependent bulk scattering resistance and increasing the film thickness, it is possible to increase the resistance change amount.

  As a magnetic material suitable for increasing the resistance change amount by increasing the bulk scattering resistance, a so-called impurity scattering effect in which a nonmagnetic element typified by copper (Cu) is added to a general CoFe-based magnetic material is used. Materials.

  However, such a ferromagnetic material containing a nonmagnetic element also has a drawback in that the spin-dependent interface scattering resistance at the interface with the nonmagnetic intermediate layer is small. It has been difficult to improve both the interface scattering and the device performance.

  In order to solve such problems, a thin film insertion layer formed of a material having a large spin-dependent interface scattering is interposed between a nonmagnetic intermediate layer such as Cu and a free layer, or between a nonmagnetic intermediate layer and a pinned layer. A configuration has been proposed in which the amount of change in resistance is increased by insertion (see, for example, Patent Document 1).

  FIG. 1 is a diagram illustrating a configuration example of a magnetoresistive effect element that increases a resistance change amount by a thin film insertion layer. The spin valve type element is provided with an upper electrode 152 and a lower electrode 154 for allowing a sense current to flow in a direction perpendicular to the film surface, and an antiferromagnetic layer 114 and a magnetization pinned on the lower electrode 154 through an underlayer 112. A layer (pinned layer) 116, a nonmagnetic intermediate layer 118, and a magnetization free layer (free layer) 120 are stacked, and are connected to the upper electrode 152 via a protective layer 122.

  As shown in FIG. 1A, the thin film insertion layers 132 and 134 formed of a material having a large spin-dependent interface scattering are free from the interface between the nonmagnetic intermediate layer 118 and the pinned layer 116 and the nonmagnetic intermediate layer 118. Inserted at the interface of layer 120.

  As shown in FIG. 1B, the thin film insertion layer 132 has at least two kinds of metals of Co, Fe, and Ni as a base element, and Cr, Ti, Mn, Cu, Au, Ag, B, C, N, Impurities such as O and F are added at 0.1 atomic% to 30 atomic%.

In this configuration, the concentration of the added impurity is set higher on the interface side with the nonmagnetic intermediate layer 118 than on the bulk side in the pinned layer 116.
JP 2003-60263 A

  In view of the background art described above, the present invention is a CPP magnetoresistive element having a spin valve structure, in which both an increase in spin-dependent interface scattering and an increase in spin-dependent bulk scattering are achieved, and the magnetoresistive effect element has a large resistance change amount. It is an issue to provide.

  In order to solve the above problems, in the present invention, the ferromagnetic layer constituting the pinned layer or free layer of the spin valve element is made of a ferromagnetic material containing an impurity element such as a nonmagnetic element, and the impurity element The concentration distribution is given in the film thickness direction so that the content (atomic%) is larger on the bulk side in the layer than on the interface side with the nonmagnetic intermediate layer.

  Specifically, for example, when using a system in which a non-magnetic element such as Cu is added to a CoFe-based ferromagnetic layer, a Cu-added element is present near the interface between the CoFe-based ferromagnetic layer and the non-magnetic intermediate layer. A film configuration in which the Cu additive element is present from a position away from the interface by a certain distance does not exist. Alternatively, even if the Cu additive element is present near the interface, the concentration is configured to be lower than the content of the Cu additive element on the bulk side.

As a first aspect of the present invention, a magnetoresistance effect element having a large magnetoresistance change is provided. Magnetoresistive element is
A first magnetic layer whose magnetization direction is changed by an external magnetic field, a second magnetic layer whose magnetization direction is fixed with respect to the external magnetic field, and the first magnetic layer and the second magnetic layer are magnetically coupled. A magnetoresistive film including a nonmagnetic intermediate layer to be separated;
An upper electrode and a lower electrode for applying a sense current in a direction perpendicular to the magnetoresistive film;
And at least one of the first and second magnetic layers is made of a ferromagnetic material to which an impurity element is added, and the amount of the impurity element added is greater in the layer than on the interface side with the nonmagnetic intermediate layer. It is set to be higher on the bulk side.

  With such a configuration, it is possible to increase the magnetoresistance change of the spin valve element having the CPP structure.

  In a favorable configuration example, the impurity element is a nonmagnetic element, and the addition amount of the nonmagnetic element on the interface side is 5 atomic% or less.

  The region where the amount of impurity element added is set lower than the bulk side is preferably within 2 nm from the interface with the nonmagnetic intermediate layer.

  On the other hand, the amount of the impurity element added on the bulk side in the layer is, for example, 5 to 20 atomic%.

  According to a second aspect of the present invention, there is provided a magnetic head comprising the magnetoresistive effect element described above and an inductive conversion element that converts a change in magnetoresistance of the magnetoresistive effect element detected by the sense current into an induced voltage. provide.

  As a third aspect of the present invention, a magnetic disk device is provided. The magnetic disk device includes a magnetic recording medium, a magnetic head provided on the second side, and an actuator arm that drives the magnetic head to a desired position on the magnetic recording medium.

  Both the spin-dependent bulk scattering resistance inside the ferromagnetic layer and the spin-dependent interface scattering resistance at the interface with the nonmagnetic intermediate layer can be kept high.

  By increasing the amount of resistance change in the portion that performs spin-dependent conduction, the output of the CPP type magnetoresistive element can be increased.

  Furthermore, high sensitivity and high output of the magnetic head using the CPP type magnetoresistive effect element can be realized.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings.

FIG. 2 illustrates a CPP (Current Current) according to an embodiment of the present invention.
1 is a schematic configuration diagram of a magnetoresistive element 10 having a (Perpendicular to Plane) structure. This magnetoresistive element 10 is used as a part of a magnetic sensor (or reproducing head element) of a magnetic head, for example.

  The magnetoresistive effect element 10 includes a magnetoresistive effect film 13, and an upper electrode 24 and a lower electrode 11 that supply a sense current in a direction perpendicular to the magnetoresistive effect film 13. The magnetoresistive effect film 13 is laminated on the lower electrode 11 via the base layer 12 and has a free layer (first magnetic layer) 20 whose magnetization direction changes when an external magnetic field is applied, and a magnetization layer that is magnetized against the external magnetic field. The pinned layer (second magnetic layer) 16 whose direction is fixed, the nonmagnetic intermediate layer 18 positioned between these two magnetic layers (the free layer 20 and the pinned layer 16), and the magnetization direction of the pinned layer 16 The antiferromagnetic layer 14 for pinning is included.

  In FIG. 2, for simplicity, a single pinned layer 16 and a nonmagnetic intermediate layer 18 are stacked, but a second nonmagnetic intermediate layer and a ferromagnetic layer are further stacked above the free layer 20. May be.

  The free layer 20 is a ferromagnetic material that exhibits magnetic soft magnetism, and is made of a material that is based on Fe, Co, and Ni and to which an impurity such as a nonmagnetic element (for example, Cu) is added.

  Similarly to the free layer 20, the pinned layer 16 is also composed of a ferromagnetic material to which impurities are added. However, the magnetization direction is fixed by the antiferromagnetic layer 14 so as to be magnetically hard. .

  The free layer 20 and the pinned layer 16 have low impurity addition layers 19 and 17 that contribute to a change in magnetoresistance in the magnetic layer with a predetermined thickness from the interface with the nonmagnetic intermediate layer 18, respectively. In the low impurity addition layers 19 and 17, the amount of the impurity addition element is set lower than the bulk portion in the layer, and in this sense, it can be called an additive element reduction region in the magnetic layer. In the example of FIG. 2, both the free layer 20 and the pinned layer 16 have the additive element reduction region, but the additive element reduction region may be set in only one of them.

  The free layer 20 and the pinned layer 16 which are magnetic layers are formed of a ferromagnetic material to which impurities such as nonmagnetic elements are added, and the added elements are reduced on the interface side with the nonmagnetic intermediate layer 18 as compared with the bulk side in the layer. By providing the region, the change in magnetoresistance can be increased.

  As a specific example, a spin valve structure film having the following configuration was produced using a DC magnetron sputtering method, and a resistance change amount was measured.

  An anti-ferromagnetic layer 14 of IrMn is formed on the underlying buffer layer 12, and a laminated structure reaching the upper protective cap film 22 is Buffer / IrMn / CoFe / Ru / CoFeCu / CoFe (low impurity addition layer) / A spin valve structure of Cu (nonmagnetic intermediate layer) / CoFe / CoFeCu / CoFe (free layer) / Cu (nonmagnetic intermediate layer) / CoFe / CoFeCu / Ru / CoFe / IrMn / Cap is formed.

  Of the pinned layer or the free layer, the thickness of CoFe on the interface side in contact with the Cu nonmagnetic intermediate and the thickness of CoFeCu on the bulk side are changed. At this time, the layer thicknesses of the pinned layer and the free layer are constant. Thereby, a region including the nonmagnetic Cu additive element and a region not including the nonmagnetic Cu additive element are set in the film thickness direction.

  The spin valve film is subjected to vacuum heat treatment in a magnetic field to enhance the pinned layer magnetization pinning force by the IrMn antiferromagnetic layer.

Above and below the spin-valve film, copper (Cu) laminated low resistance terminal to the base, by photolithography, 4 terminals with varying junction area of the spin valve film to 0.1μm ² ~1μm ² Formed in structural elements. Using a four-terminal method, resistance change characteristics of the CPP element at room temperature were measured by applying an external magnetic field of ± 1000 Oe.

  FIG. 3 shows the position where the nonmagnetic Cu-added element starts to exist from the interface of the Cu intermediate layer in the CoFe-based ferromagnetic layer, and the magnetoresistance change ΔRA of the CPP element (that is, the magnetoresistance change ΔR and the junction area A). It is a graph which shows the relationship with (product). FIG. 3B is an enlarged view of the first three points in FIG.

  The point a in FIG. 3B shows the case where the entire ferromagnetic layer is made of a CoFeCu material. The point b in FIG. 3B is a configuration in which a CoFeCu bulk film containing a Cu additive element starts from a position of 0.5 nm from the Cu intermediate layer interface, and the point c is a position of 1 nm from the Cu intermediate layer interface. In this configuration, the bulk film starts.

  FIG. 4 is a schematic diagram showing the film configuration at these three points. In FIG. 4A, the Cu intermediate layer 18 and the CoFeCu constituting the bulk of the pinned layer 16 are in contact with each other without including the low impurity addition amount layer 17 as the Cu additive element reduction region. In FIG. 4B, a CoFe low impurity addition layer 17 containing no Cu additive element is inserted at a thickness of 0.5 nm on the interface side with the Cu intermediate layer 18. In FIG. 4C, a CoFe low impurity addition amount layer 17 that does not contain a Cu addition element is inserted with a thickness of 1 nm.

  Further, the content of the Cu-added element on the bulk side is 10 atomic% with respect to 90 atomic% of CoFe.

  As is apparent from the graph of FIG. 3A, ΔRA increases in the range where the nonmagnetic Cu additive element is not present in the range of 0.1 nm to 2.0 nm from the Cu intermediate layer interface. If the starting position of the nonmagnetic Cu additive element further enters the bulk side of the ferromagnetic layer, ΔRA decreases conversely, making it meaningless to provide a Cu additive element reduction region (low impurity addition amount layer) at the interface.

  That is, by setting an additive element reduction region that does not contain a Cu additive element or contains a Cu additive element at a lower concentration (5 atomic% or less) than the bulk side within a range of 2 nm or less in the vicinity of the interface of the Cu intermediate layer. Change can be improved.

  In the example shown in FIG. 3 and FIG. 4, the amount of Cu additive element in the low impurity addition layer (addition element reduction region) 17 is zero, but it may be in a range smaller than the addition amount of the non-magnetic element on the bulk side. For example, a Cu additive element may be added to the low impurity addition layer 17 in a range of 5 atomic% or less, for example.

  At the interface with the Cu intermediate layer 18, the spin-dependent interface scattering resistance increases as the concentration of the nonmagnetic additive element in the CoFe ferromagnetic layer is lower. On the other hand, inside the CoFe-based ferromagnetic layer (bulk side), the Cu-added element concentration is high, and the effect of increasing the spin-dependent bulk scattering resistance can be obtained.

  From these results, the concentration of the nonmagnetic Cu additive element is set low (5 atomic% or less) within 2 nm from the interface with the Cu intermediate layer 18, preferably within the range of 0.5 nm to 1 nm. In the region entering the bulk side, it can be seen that it is desirable to obtain a higher ΔRA by setting the concentration of the nonmagnetic Cu additive element to a higher value, for example, 5 to 20 atomic%.

  Further, in the CoFe ferromagnetic material, the atomic ratio of Co and Fe is preferably 40 to 60% in order to obtain a high ΔRA.

  In the above-described example, the example in which the concentration change of the Cu-added element is changed in the film thickness direction in the CoFe-based ferromagnetic layer is not limited to this example, but the ferromagnetic layer includes Co, Fe, Ni, Any ferromagnetic material based on these alloys or a combination of non-magnetic elements called magnetic semiconductors may be used. Further, the same effect can be obtained by using an arbitrary nonmagnetic element such as Cr, Ti, Ta, Pt, Au, Ag, or Ta as the impurity element to be added.

  FIG. 5 is a schematic configuration diagram of a magnetic disk device 50 using the above-described magnetoresistance effect element. The magnetic disk device 50 includes a magnetic disk 51 that is a recording medium, a spindle 52 that is mounted with the magnetic disk 51 and is rotated by a drive mechanism (not shown), and a magnetic head assembly 53 that reads and writes the magnetic disk 51. . The magnetic head assembly 53 reads a magnetic field generated on the magnetic disk 51 or magnetically writes information on the magnetic disk 51, and an actuator arm 57 that drives the magnetic head 60 to a desired position on the magnetic disk 51. And a suspension 55 for holding the magnetic head 60 at the tip.

  FIG. 6 is a schematic configuration diagram of the magnetic head 60 shown in FIG. The magnetic head 60 includes a head slider (base) 61 that runs over the magnetic disk 51 in a state of being very close to the disk surface, rails 62 and 63 that form an air bearing surface with respect to the disk surface, and a coil 64. And a recording head element 66 for writing information to the magnetic disk 51 and a reproducing head element (magnetic sensor) 65 for reading information recorded on the magnetic disk 51. The main part of the reproducing head element 65 has a structure shown in FIGS.

  The reproducing head element 65 detects the time change of the magnetic field leaking from the magnetic disk 51 moving relative to the magnetic head 60 by the magnetoresistive effect element 10 (FIG. 2), and inductively converts the resistance change into a voltage. Get the output.

  The recording head element 66 applies a current to the write coil 64 to generate a magnetic flux having a direction and strength corresponding to the signal, and forms a magnetic domain corresponding to the signal on a track (not shown) of the magnetic disk 51. To write.

  Since the magnetic head 60 according to the present embodiment uses a magnetoresistive effect element having a large magnetoresistance change, the output of the head can be increased.

Finally, the following notes are disclosed regarding the above description.
(Additional remark 1) The 1st magnetic layer from which a magnetization direction changes with an external magnetic field, the 2nd magnetic layer with which the magnetization direction was fixed with respect to the said external magnetic field, and the said 1st magnetic layer and a 2nd magnetic layer A magnetoresistive film including a nonmagnetic intermediate layer for magnetically separating
An upper electrode and a lower electrode for applying a sense current in a direction perpendicular to the magnetoresistive film;
And at least one of the first and second magnetic layers is made of a ferromagnetic material to which an impurity element is added,
The magnetoresistive effect element is characterized in that the additive amount of the impurity element is set to be higher on the bulk side in the layer than on the interface side with the nonmagnetic intermediate layer.
(Additional remark 2) The said impurity element is a nonmagnetic element, The addition amount of the said nonmagnetic element in the said interface side is 5 atomic% or less, The magnetoresistive effect element of Additional remark 1 characterized by the above-mentioned.
(Supplementary note 3) The magnetoresistive effect element according to supplementary note 1, wherein the region where the amount of the impurity element added is set lower than the bulk side is within a range of 2 nm from the interface with the nonmagnetic intermediate layer. .
(Supplementary note 4) The magnetoresistive effect element according to supplementary note 1, wherein an addition amount of the impurity element on the bulk side in the layer is 5 to 20 atomic%.
(Additional remark 5) The said 1st and 2nd magnetic layer is comprised with the material which added the nonmagnetic addition element to the material based on Co, Fe, Ni, and these alloys. Additional remark 1 characterized by the above-mentioned. 2. The magnetoresistive effect element described in 1.
(Appendix 6) The magnetoresistive effect element according to any one of Appendixes 1 to 5,
A magnetic head comprising: an inductive conversion element that converts a change in magnetoresistance of the magnetoresistive effect element detected by the sense current into an induced voltage.
(Additional remark 7) The magnetic head of Additional remark 6 further provided with the recording head element which generate | occur | produces the intensity | strength and the magnetic flux of a direction according to an input signal.
(Appendix 8) Magnetic recording medium;
The magnetic head according to appendix 6 or 7,
And an actuator arm that drives the magnetic head to a desired position on the magnetic recording medium.

It is a figure which shows the structural example of the well-known magnetoresistive effect element which increases resistance variation. It is a schematic block diagram of the magnetoresistive effect element of the CPP structure which concerns on one Embodiment of this invention. It is a graph which shows the relationship between resistance variation | change_quantity and the position from the Cu intermediate | middle layer interface where a nonmagnetic addition element begins to exist in a ferromagnetic layer. It is a figure which shows the film | membrane structural example in 3 points | pieces of FIG.3 (b). FIG. 3 is a schematic configuration diagram of a magnetic disk device including a magnetic head using the magnetoresistive effect element shown in FIG. 2. FIG. 6 is a schematic diagram of the magnetic head of FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Magnetoresistive element 11 Lower electrode 12 Underlayer 13 Magnetoresistive film (spin valve film)
14 Antiferromagnetic layer 16 Pinned layer (second magnetic layer)
17, 19 Low impurity addition layer 18 Nonmagnetic intermediate layer 20 Free layer (first magnetic layer)
22 Protective layer 24 Upper electrode 50 Magnetic disk device 60 Magnetic head 65 Reproducing head element (magnetic sensor)
66 Recording head element

Claims (5)

A first magnetic layer whose magnetization direction is changed by an external magnetic field, a second magnetic layer whose magnetization direction is fixed with respect to the external magnetic field, and the first magnetic layer and the second magnetic layer are magnetically coupled. A magnetoresistive film including a nonmagnetic intermediate layer to be separated;
An upper electrode and a lower electrode for applying a sense current in a direction perpendicular to the magnetoresistive film;
And at least one of the first and second magnetic layers is made of a ferromagnetic material to which an impurity element is added,
The magnetoresistive effect element is characterized in that the additive amount of the impurity element is set to be higher on the bulk side in the layer than on the interface side with the nonmagnetic intermediate layer.   2. The magnetoresistive element according to claim 1, wherein the impurity element is a nonmagnetic element, and the amount of the nonmagnetic element added on the interface side is 5 atomic% or less.   2. The magnetoresistive element according to claim 1, wherein the region in which the amount of the impurity element added is set lower than the bulk side is within a range of 2 nm from the interface with the nonmagnetic intermediate layer.   The magnetoresistive effect element according to claim 1, wherein the addition amount of the impurity element on the bulk side in the layer is 5 to 20 atomic%. The magnetoresistive effect element according to any one of claims 1 to 4,
A magnetic head comprising: an inductive conversion element that converts a change in magnetoresistance of the magnetoresistive effect element detected by the sense current into an induced voltage.

Images