JP2005072608A - Magnetoresistance effect element, magnetic head, and magnetic reproducing equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manetoresistance effect element having an improved electronic reflective layer at free layer side which can get a magnetoresistive increase effect, a magnetic head, and magnetic reproducing equipment. <P>SOLUTION: The element comprises magnetic adhesive layer having a ferromagnetic film in which the direction of magnetization is substantially adhered in one direction, magnetic free layer having a ferromagnetic film in which the direction of magnetization changes in accordance with external magnetic field, and non-magnetism interlayer arranged between the above-mentioned magnetic adhesive layer and magnetic free layer. Further, the element is characterized in that high conductive layer having a conductivity higher than those of the above-mentioned magnetic adhesive layer and magnetic free layer is laminated at the opposite side in comparison to the above-mentioned non-magnetism interlayer when seeing from the above-mentioned magnetic free layer side, and a layer which is formed by irradiating ionized gas having the main component of oxide of element different from a main element constituting this high conductive layer to the high conductive layer is laminated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnetoresistive effect element, a magnetic head, and a magnetic reproducing apparatus. More specifically, the present invention relates to a magnetoresistive effect element using a spin valve film provided with an electron reflecting layer, and this magnetoresistive effect element. The present invention relates to a magnetic head used and a magnetic reproducing apparatus equipped with the magnetic head.

  With the invention of a magnetic head using a giant magnetoresistive effect (GMR) by a spin-valve (SV) film, the magnetic recording density has been greatly improved in recent years. SV is a non-magnetic layer (referred to as “spacer layer” or “non-magnetic intermediate layer”) sandwiched between two metallic ferromagnetic layers, and one ferromagnetic layer (“pinned layer” or “magnetization”). The magnetization of the other ferromagnetic layer (referred to as “free layer” or “magnetization free layer”) is recorded while the magnetization of the fixed layer is fixed by a bias magnetic field or the like. By changing relative to the pinned layer according to the magnetic field from the medium, a huge magnetoresistance can be obtained (Phys. Rev. B., Vol. 45, 806 (1992), J. Appl. Phys., Vol. 69, 4774 (1991) etc.).

  Until now, various ideas have been made to improve the sensitivity of the magnetic head using the SV film. Among them, a specular spin-valve (SPSV) film that improves the magnetoresistive change rate by using specular reflection of electrons as a method for improving the magnetoresistive change rate of the SV film is 50 gigabits. Much attention has been paid as a technology for realizing a recording density of at least square inch (Gbpsi).

  In SPSV, an oxide layer is stacked on a free layer or a pinned layer, and electron reflection at the interface is used to extend the mean free path to obtain a larger magnetoresistance effect (WFEgelhoff et al. J. Appl. Phys. 78 (1), 1 July 1995). So far, in order to use SPSV as a practical device, a structure in which an oxide layer of several nanometers is inserted into a pinned layer, a structure in which an oxide layer is stacked on a free layer, and the like have been proposed.

  As the electron reflecting layer on the free layer side, MR (MagnetoResistance) improvement results have been reported in a structure in which Ta, Fe, Ni, and Al oxides are directly stacked on the free layer magnetic layer. In addition, even in an SV film using a spin filter structure (Spin Filter: SF), the effect of increasing MR by an electron reflecting layer has been reported.

  SF is a structure in which a high-conductivity layer is laminated on a free layer, which is advantageous in designing a bias point for output of a magnetic head, and is indispensable in a magnetic head compatible with high recording density. In this SF structure, an MR improvement effect has been reported in a structure in which a Ta oxide is formed on a Cu highly conductive layer. A structure in which 10 nm of NiO is formed on a Cu high-conductivity layer has also been reported.

  However, among these oxides, oxides such as Ta, Fe, and Al are amorphous (amorphous) or a mixed phase in which the crystal structure is dispersed. In such a case, the electron reflection effect is reduced, and a sufficient increase in MR cannot be obtained. Further, in terms of heat resistance, these fine structures are likely to cause diffusion and transformation, leading to deterioration of MR characteristics. NiO cannot be said to have sufficiently good film quality unless it has a thickness of about 10 nm, and MR enhancement due to the electron reflection effect is small.

  As the recording density increases, the total thickness of the SV film is required to be thinner, and the electron reflection layer reaching 10 nm as described above is difficult to use in the device from this viewpoint.

  Furthermore, when producing a magnetic head mounted with an SV film, alumina is formed as insulating layers above and below the SV film. If alumina is simply formed on an amorphous oxide, oxygen from the oxide to the alumina is formed. As a result, a partial oxygen deficiency state occurs in the electron reflecting layer or a portion that is reduced to metal appears.

Further, milling is performed in the process of processing into a magnetic head, but it is generally necessary to stack Ta metal on the top of several nm as a protective film. However, in this case as well, O ₂ is absorbed by the Ta metal, a part of the electron reflecting layer is reduced, and an oxygen deficient part or a reduced metal part appears in the electron reflecting layer. These are a major cause of reducing the electron reflection effect, leading to a reduction in output, and a cause of deterioration in long-term heat resistance.

  As described above, the conventional structure in which the oxide electron reflective layer is laminated on the free layer side has improved MR, but has many problems and is difficult to put into practical use as a device for practical use.

  The present invention has been made based on the recognition of such a problem, and an object of the present invention is to propose a structure for improving the electron reflection layer on the free layer side that can obtain an MR enhancement effect. That is, a structure of an electron reflection layer that can provide a high electron reflection effect, a magnetoresistive effect element that can maintain good characteristics even when mounted on a magnetic head structure as a device for practical use, and a magnetic device equipped with the magnetoresistive effect element An object is to provide a head and a magnetic reproducing apparatus.

  In order to achieve the above object, a first magnetoresistance effect element of the present invention includes a magnetization fixed layer having a ferromagnetic film in which the magnetization direction is fixed substantially in one direction, and the magnetization direction in an external magnetic field. A magnetization free layer having a ferromagnetic film that changes in response, a nonmagnetic intermediate layer provided between the magnetization pinned layer and the magnetization free layer, and the nonmagnetic intermediate layer as viewed from the magnetization free layer A high-conductivity layer having higher conductivity than the magnetization pinned layer and the magnetization free layer, and a high-conductivity layer provided on the opposite side of the magnetization free layer as viewed from the high-conductivity layer. A magnetoresistive effect element comprising: a non-magnetic crystal layer which contains a compound of an element different from the main element to be formed as a main component, is substantially non-magnetic, and is substantially crystalline. .

  An SF (spin filter) structure in which a high-conductivity layer is stacked on a magnetization free layer is an indispensable configuration for designing a bias point, and at the same time, includes a nonmagnetic crystal layer and a free layer that also function as an electron reflection layer. It is necessary to stop the diffusion and obtain good soft magnetic properties of the free layer. The nonmagnetic crystal layer laminated thereon needs to change abruptly in order to obtain good electron reflection, and from this point of view, it is desirable to be crystalline. In addition, if a mixed layer in which a plurality of phases are mixed is present, the electron potential distribution at the interface is distributed, so that sufficient electron reflection characteristics cannot be obtained. For this reason, it is desirable that it is a single phase.

  Here, the nonmagnetic crystal layer includes B, Si, Ge, W, Nb, Mo, P, V, Sb, Zr, Ti, Zn, Pb, Zr, Cr, Sn, Ga, Fe, Co, and rare earth metal. It is desirable that at least one of these oxides be the main component.

  These have higher binding energy with oxygen than Cu (copper), which is mainly used as a high-conductivity electronic layer, and are easy to oxidize, so that stable oxides are easily obtained, and oxygen diffusion at the interface with Cu It is because it is hard to occur.

  In these magnetoresistive elements, the nonmagnetic crystal layer is desirably 5 nm or less. This is because if it is too thick, it comes out of a range that satisfies the demand for thinning, which comes from the demand for high magnetic recording density. On the other hand, when the thickness is 0.5 nm or less, it becomes difficult to obtain a uniform film quality by heat treatment or the like, and the electron reflection characteristics are deteriorated. Therefore, it is desirable that it is 0.5 nm or more.

  On the other hand, the second magnetoresistance effect element of the present invention includes a magnetization pinned layer having a ferromagnetic layer whose magnetization direction is substantially pinned in one direction, and a ferromagnetic layer whose magnetization direction changes according to an external magnetic field. A magnetization free layer having a layer, a nonmagnetic intermediate layer provided between the magnetization pinned layer and the magnetization free layer, and provided on the opposite side of the nonmagnetic intermediate layer as viewed from the magnetization free layer, A high-conductivity layer having a higher conductivity than the magnetization pinned layer and the magnetization free layer, and a main element constituting the high-conductivity layer provided on the opposite side of the magnetization free layer as viewed from the high conductivity layer A first compound layer containing a compound of an element as a main component; and a second compound layer provided on the side opposite to the highly conductive layer as viewed from the first compound layer. To do.

  Here, the “compound” means, for example, an oxide, nitride, boride, carbide or the like.

  Here, in the case where the first compound layer is an oxide of the same material as the highly conductive layer, since the oxidation energy is the same, oxygen diffusion tends to occur in the electron reflecting layer. Therefore, it is desirable that the oxide is a different substance. At this time, it is desirable to provide a diffusion barrier layer in order to prevent mainly the diffusion of oxygen between the protective layer or the insulating layer stacked on the first compound layer.

The first compound layer includes B, Si, Ge, Ta, W, Nb, Al, Mo, P, V, As, Sb, Zr, Ti, Zn, Pb, Al, Sb, Th, Be, Zr, Cd, Sc, La, Y, Pt, Cr, Sn, Ga, Cu, In, Th, Rh, Pd, Pb, Mg, Li, Zn, Ba, Ca, Sr, Mn, Fe, Co, Ni, The main component is an oxide of the first element selected from the sequence of elements Cd and Rb,
The second compound layer can form an oxide more stably when the main component is an oxide of an element located after the first element in the order of the elements.

  This is because, in the above-mentioned order, the later the position, the lower the binding energy with oxygen and the less the oxidation, so that it can function as a barrier that stops the diffusion of oxygen in the oxide layer closest to the highly conductive layer.

  In these magnetoresistive elements, the electron reflection layer is desirably 5 nm or less. This is because if it is too thick, it comes out of a range that satisfies the demand for thinning, which comes from the demand for high magnetic recording density. On the other hand, when the thickness is 0.5 nm or less, it becomes difficult to obtain a uniform film quality by heat treatment or the like, and the electron reflection characteristics are deteriorated. Therefore, it is desirable that it is 0.5 nm or more.

  In addition, the thickness of the magnetization free layer should be as thin as possible in order to effectively contribute to the MR improvement of the electron reflection effect. Specifically, the thickness is desirably 5 nm or less. However, if the thickness is too thin, the MR effect is significantly reduced due to the difference in mean free path between up-spin electrons and down-spin electrons, so that the thickness is preferably 1 nm or more. In addition, the magnetization free layer may be a Co alloy or a laminated structure of Co alloy and Ni alloy, but in order to obtain an electron reflection effect, electron scattering that does not contribute to MR can be avoided when the laminated interface is small. Therefore, it is preferable to use a single-layer Co alloy.

On the other hand, the third magnetoresistance effect element of the present invention includes a magnetization fixed layer having a ferromagnetic film in which the magnetization direction is substantially fixed in one direction, and a ferromagnetic material whose magnetization direction changes in accordance with an external magnetic field. A magnetization free layer having a film, and a nonmagnetic intermediate layer provided between the magnetization pinned layer and the magnetization free layer,
On the side opposite to the nonmagnetic intermediate layer as viewed from the magnetization free layer, a highly conductive layer having higher conductivity than the magnetization pinned layer and the magnetization free layer is laminated,
A feature is that a layer formed by irradiating an ionized gas with an oxide of an element different from the main element constituting the highly conductive layer as a main component is laminated on the highly conductive layer.

The fourth magnetoresistance effect element of the present invention includes a magnetization fixed layer having a ferromagnetic film in which the magnetization direction is substantially fixed in one direction, and a ferromagnetic material in which the magnetization direction changes according to an external magnetic field. A magnetization free layer having a film, and a nonmagnetic intermediate layer provided between the magnetization pinned layer and the magnetization free layer,
On the opposite side of the magnetization free layer from the non-magnetic intermediate layer, a highly conductive layer having higher conductivity than the magnetization pinned layer and the magnetization free layer is laminated, and the highly conductive layer includes the highly conductive layer. The main component is an oxide of an element different from the main element, and a layer formed by irradiating a plasma gas is laminated.

  In these magnetoresistive elements, it is necessary to adjust the thickness of the highly conductive layer in order to obtain a current magnetic field required for adjusting the bias point. Therefore, the thickness is desirably 3 nm or less. More preferably, it is 2 nm or less. On the other hand, when the thickness is 0.5 nm or less, diffusion of oxygen or the like occurs between the layer acting as the electron reflection layer and the soft magnetic characteristics are hindered. In particular, when the electron reflection layer has a magnetic order such as an antiferromagnetic material, there is a possibility that magnetic coupling may occur. Therefore, 0.5 nm or more is necessary, and preferably 0.8 nm or more is desirable. .

On the other hand, the fifth magnetoresistance effect element of the present invention includes a magnetization pinned layer having a ferromagnetic film whose magnetization direction is substantially fixed in one direction, and a ferromagnetic material whose magnetization direction changes according to an external magnetic field. A magnetization free layer having a film, a nonmagnetic intermediate layer provided between the magnetization pinned layer and the magnetization free layer, and provided on the opposite side of the nonmagnetic intermediate layer as viewed from the magnetization free layer, Cu A metal layer mainly composed of at least one of Au, Ag, Ru, Ir, Re, Rh, Pt, Pd, Al, Os, and Ni;
It is provided on the side opposite to the magnetization free layer as viewed from the metal layer, contains a compound of an element different from the main element constituting the highly conductive layer as a main component, is substantially non-magnetic, and substantially A non-magnetic crystal layer made of crystalline,
It is provided with.

  The sixth magnetoresistance effect element according to the present invention includes a magnetization pinned layer having a ferromagnetic layer in which the magnetization direction is substantially pinned in one direction, and a ferromagnetic layer whose magnetization direction changes according to an external magnetic field. A magnetization free layer having a layer, a nonmagnetic intermediate layer provided between the magnetization pinned layer and the magnetization free layer, and provided on the opposite side of the nonmagnetic intermediate layer as viewed from the magnetization free layer, Cu , Au, Ag, Ru, Ir, Re, Rh, Pt, Pd, Al, Os and Ni as a main component, and the magnetization free layer as viewed from the metal layer, A first oxide layer provided on the opposite side; and a second oxide layer provided on the opposite side to the highly conductive layer as viewed from the first oxide layer. To do.

  In any of the above magnetoresistive effect elements, the electron reflection effect can be further enhanced by forming the electron reflection layer in the magnetization fixed layer in the magnetization fixed layer. That is, since the electronic mirror reflection occurs on both sides, the same structure as the magnetic multilayer film can be obtained in a pseudo manner.

  In the above structure, the pinned layer and the magnetic layer of the pinned layer can be combined with a structure called a synthetic antiferromagnetic structure in which Ru (ruthenium) is formed between the ferromagnetic layers. Can increase stability.

  In these SV films, an Mn-based antiferromagnetic material such as PtMn, IrMn, NiMn, FeMn, RhMn, and RuMn can be used as the exchange bias film of the pinned layer.

  These magnetoresistive elements are effective in both the bottom type SV in which the antiferromagnetic film is formed below the pinned layer and the top type SV in which the antiferromagnetic film is formed above the pinned layer in the stacking order. is there.

  The magnetoresistive element described above can be used as a magnetic head for reading recorded data on a medium in a magnetic recording / reproducing apparatus. It can also be used as an MRAM (magnetic random access memory).

  As described above, according to the present invention, it is possible to obtain good electron reflection characteristics, good heat resistance, and reliability by using a crystalline oxide as the electron reflection layer on the free layer side.

  Further, according to the present invention, oxygen diffusion can be further suppressed by forming the electron reflecting layer on the free layer side to have a laminated structure of two or more layers.

  As a result, a magnetic recording / reproducing technique having a recording density of 50 Gbpsi or higher can be realized, and the industrial merit is great.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a conceptual diagram showing a cross-sectional configuration of a main part of a magnetoresistive effect element according to a first embodiment of the present invention. That is, the magnetoresistive effect element according to the present embodiment includes an underlayer 11, an antiferromagnetic layer 12, a pinned layer 13, a nonmagnetic intermediate layer 14, a free layer 15, a highly conductive layer 16, and an electron reflecting layer on a substrate (not shown). The layer 17 and the protective layer 20 are stacked in this order.

  In the present embodiment, the electron reflecting layer 17 provided on the free layer 15 side is not amorphous but is formed of a substantially crystalline single layer. The crystalline single layer means that the electron reflecting layer 17 is made of a single crystal or a polycrystal. For example, it means that it is not a mixed layer in which fine crystal grains are scattered in an amorphous state. is there.

  Thus, by making the electron reflection layer 17 provided outside the free layer 15 a single crystalline layer, it is possible to improve the electron reflection characteristics and at the same time to stabilize it thermally. That is, if a single crystalline layer is used, a steep potential distribution can be formed at the interface with the highly conductive layer 16, and electrons can be effectively reflected.

  Further, if the electron reflecting layer 17 is amorphous or a mixed layer of amorphous and fine crystal grains, diffusion and phase transformation are likely to occur at a high temperature, and the atomic composition distribution at the interface with the highly conductive layer 16 loses steepness. It becomes easy. As a result, the potential distribution also loses steepness and the electron reflection characteristics deteriorate.

  On the other hand, according to the present embodiment, by making the electron reflecting layer 17 a single crystalline layer, atomic diffusion and phase transformation are less likely to occur even in a high temperature state. It can be stabilized. As a result, high electron reflection characteristics can be maintained.

  Here, whether or not it is “crystalline” can be determined from a lattice image obtained by TEM (transmission electron microscopy) observation. That is, if an ordered arrangement is observed in the lattice image, it can be determined that the crystal is crystalline.

  Alternatively, when a spot-like pattern is observed in the electron beam diffraction image, it can be determined that the irradiation range of the electron beam is substantially a single crystal and is “crystalline”. When a ring-shaped pattern is obtained in the electron beam diffraction image, it can be determined that the irradiation range of the electron beam is in a polycrystalline state and is “crystalline”.

Desirable materials constituting the electron reflecting layer 17 are B, Si, Ge, W, Nb, Mo, P, V, Sb, Zr, Ti, Zn, Pb, Zr, Cr, Al, Sn, Ga, Fe. , An oxide containing at least one selected from rare earth metals. Of these, non-magnetic oxides are desirable. The term “non-magnetic” as used herein means “paramagnetism”, “antiferromagnetism” or “diamagnetism”, and means no spontaneous magnetization. Among these, thermally stable oxides mainly composed of SiO ₂ , W—O, Nb—O, Mo—O, V—O, TiO, Cr ₂ O ₃ , Fe ₂ O ₃ , and Al ₂ O ₃ are It is also desirable from the viewpoint of heat resistance.

  Whether or not they are “non-magnetic” can be determined by measuring the magnetization of a bulk or thin film of the same composition from the results obtained by composition analysis such as EDX (Energy Dispersive X-ray spectroscopy). it can.

  As a material of the protective layer 20 provided on the electron reflecting layer 17, Ta (tantalum) or mainly amorphous (amorphous) alumina as an insulating layer is laminated. Since these materials contain elements such as Ta and Al that are easily oxidized, oxygen is easily absorbed from the electron reflecting layer 17. However, according to the present embodiment, a sufficiently stable oxide can be obtained by making the electron reflecting layer 17 “crystalline”. As a result, oxygen diffusion from the electron reflecting layer 17 to the protective layer 20 can be suppressed.

  A method of forming an oxide of the electron reflecting layer 17 can be created by introducing oxygen into the chamber, creating by an oxidation treatment containing radical oxygen, or irradiating with ionized gas. In particular, by using an active state reaction gas, an oxide having higher stability and a stable crystal structure can be formed. At this time, the reaction gas itself may be ionized and irradiated, or argon, xenon, or neon may be ionized and irradiated into the chamber from another place.

  At this time, if the influence of the reaction gas reaches the highly conductive layer, the thermal stability is deteriorated and the MR is deteriorated. Therefore, the reaction must be stopped at the interface with the highly conductive layer. Therefore, it is easier to form a chemically strong treatment using an active gas and at the same time a weak strength.

  Alternatively, the film can be formed by sputtering, but at this time, the film formed by ion beam sputtering is easier to control than the film formed by RF sputtering, so that a good crystalline film can be obtained.

  The film thickness of the electron reflecting layer 17 needs to be 0.5 nm or more in order to obtain thermal stability and uniform film quality. On the other hand, when the electron reflecting layer 17 is formed to a thickness of 5 nm or more, it becomes difficult to insert the electron reflecting layer 17 at a distance between shields corresponding to high-density recording when a magnetic head is formed. For this reason, the thickness of the electron reflecting layer 17 is desirably 5 nm or less.

  In addition, the film thickness of the free layer 15 should be as thin as possible in order to effectively contribute to the MR improvement of the electron reflection effect. Specifically, the thickness is desirably 5 nm or less. However, if the thickness is too thin, the MR effect is significantly reduced due to the difference in mean free path between up-spin electrons and down-spin electrons, so that the thickness is preferably 1 nm or more.

  The free layer 15 may be a Co alloy or a laminated structure of a Co alloy and a Ni alloy, but in order to obtain an electron reflection effect, electron scattering that does not contribute to MR can be avoided when the laminated interface is smaller. Therefore, it is preferable to use a single-layer Co alloy.

  On the other hand, the pinned layer 13 may have a structure having an electron reflecting layer (not shown) in the pinned layer 13 or may have a synthetic antiferromagnetic structure at the same time. When a synthetic antiferromagnetic structure is not used, a ferromagnetic layer (not shown) may be formed as a bias adjustment layer below the antiferromagnetic exchange bias film 12. The synthetic antiferromagnetic structure may be bonded using Ru (ruthenium), or an electron reflecting layer itself (not shown) may be responsible for antiferromagnetic coupling. This can be obtained by controlling the film thickness of an oxide antiferromagnetic material or an oxide ferrimagnetic material.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.
FIG. 2 is a conceptual diagram showing a cross-sectional configuration of a main part of the magnetoresistive effect element according to the present embodiment. That is, on the substrate (not shown), the underlayer 11, the antiferromagnetic layer 12, the pinned layer 13, the nonmagnetic intermediate layer 14, the free layer 15, the highly conductive layer 16, the first electron reflecting layer 17, the second layer The electron reflecting layer 18 and the protective layer 20 are stacked in this order. That is, in this configuration, two or more electron reflecting layers 17 and 18 are provided on the free layer side.

  In the present embodiment, a chemically stable electron reflecting effect can be obtained by appropriately selecting the materials of the two electron reflecting layers. That is, by stacking two or more materials having different binding energies with oxygen, oxygen diffusion can be suppressed and a good electron reflection interface can be maintained.

In concrete terms, the first electron-reflecting layer 17 close to the free layer 15, than the second electron-reflecting layer 18 farther from the free layer 15 is composed of an oxide of easily oxidizable elements. In this way, the second electron reflecting layer 18 functions as a barrier that prevents oxygen from diffusing from the first electron reflecting layer 17 to the protective layer 20.

  That is, as the material of the protective layer 20 formed on the electron reflecting layers 17 and 18, Ta (tantalum), or mainly amorphous (amorphous) alumina as an insulating layer is laminated. Since these materials contain elements such as Ta and Al that are easily oxidized, oxygen is easily absorbed from the electron reflection layer in the vicinity. On the other hand, according to the present embodiment, even if oxygen diffusion from the second electron reflective layer 18 close to the protective layer 20 to the protective layer 20 occurs, the first electron reflective layer 17 to the second electron reflective layer 17 Oxygen does not easily flow out to the electron reflecting layer 18. This is because the first electron reflecting layer 17 contains an element that is more easily oxidized. That is, the second electron reflecting layer 18 acts as a “barrier” against oxygen diffusion, and the outflow of oxygen from the first electron reflecting layer 17 can be effectively prevented.

  More specifically, the first electron reflecting layer 17 includes B, Si, Ge, Ta, W, Nb, Al, Mo, P, V, As, Sb, Zr, Ti, Zn, Pb, Al, and Sb. , Th, Be, Zr, Cd, Sc, La, Y, Pt, Cr, Sn, Ga, Cu, In, Th, Rh, Pd, Pb, Mg, Li, Zn, Ba, Ca, Sr, Mn, Fe , Co, Ni, Cd, and Rb, and the second electron reflecting layer 18 is formed of an oxide of a substance containing a first element selected from the group consisting of the first element. It is assumed that the layer 17 is made of an oxide including a second element selected from elements arranged on the right side of the first element included in the layer 17.

  In the arrangement of the above elements, as it goes from the left to the right, the binding energy with oxygen becomes lower and the oxidation becomes difficult. That is, as described above, if the first electron reflecting layer 17 is formed of the oxide of the element on the left side, the electron reflecting layer 17 becomes more stable than the second electron reflecting layer 18, and the second electron The reflective layer 18 functions as a barrier that prevents diffusion of oxygen.

  As described above, Ta, amorphous alumina, or the like is formed as the protective layer 20, but if amorphous alumina is formed directly on the electron reflecting layer 18, oxygen absorption is intense. It is good to laminate alumina.

  When the first electron reflecting layer 17 closest to the high conductive layer 16 is crystalline as in the first embodiment, even better electron reflecting characteristics can be obtained, but the structure for preventing oxygen diffusion as in this embodiment. If it is taken, good characteristics can be stably obtained to some extent even in an amorphous state.

  Specific combinations of the first electron reflecting layer 17 and the second electron reflecting layer 18 outside the first electron reflecting layer 17 include Ta oxide for the former, Ni oxide for the latter, Ta oxide for the former, and Al oxide for the latter. Alternatively, good characteristics can be obtained by using a composition mainly composed of either Cr oxide for the former, Ni oxide for the latter, Al oxide for the former, or Ni oxide for the latter.

  Examples of a method of forming these oxides include a method of forming by an oxidation treatment containing radical oxygen, a method of forming by irradiating a gas containing ionized oxygen, and the like. Alternatively, the film can be formed by sputtering. At this time, the film formed by ion beam sputtering is easier to control than the film formed by RF sputtering, so that a film with good crystallinity can be obtained.

  The film thicknesses of the electron reflecting layers 17 and 18 are desirably 0.5 nm or more in order to obtain thermal stability and uniform film quality. On the other hand, if the thickness is 5 nm or more, it becomes difficult to insert the magnetic head at a distance between shields corresponding to high-density recording when the magnetic head is formed. For this reason, it is desirable to make it 5 nm or less.

  In addition, the film thickness of the free layer 15 should be as thin as possible in order to effectively contribute to the MR improvement of the electron reflection effect. Specifically, the thickness is desirably 5 nm or less. However, if the thickness is too thin, the MR effect is significantly reduced due to the difference in mean free path between up-spin electrons and down-spin electrons, so that the thickness is preferably 1 nm or more.

  The free layer 15 may be a Co alloy or a laminated structure of a Co alloy and a Ni alloy, but in order to obtain an electron reflection effect, electron scattering that does not contribute to MR can be avoided when the laminated interface is smaller. Therefore, it is preferable to use a single-layer Co alloy.

  On the other hand, the pinned layer 13 may have a structure having an electron reflecting layer (not shown), and may be a synthetic antiferromagnetic structure at the same time. When a synthetic antiferromagnetic structure is not used, a ferromagnetic layer (not shown) may be formed as a bias adjustment layer under the antiferromagnetic layer 12 serving as an antiferromagnetic exchange bias film. The synthetic antiferromagnetic structure may be coupled using Ru, or an electron reflection layer (not shown) may be responsible for antiferromagnetic coupling. This can be obtained by controlling the film thickness of an oxide antiferromagnetic material or an oxide ferrimagnetic material.

  In the specific examples described above, the case where the electron reflecting layer has a two-layer structure is illustrated, but the present invention is not limited to this, and the electron reflecting layer may have a three-layer structure or more.

  FIG. 3 is a conceptual diagram illustrating the configuration when the electron reflection layer has a three-layer configuration. That is, in the spin valve element shown in the figure, the first electron reflecting layer 17, the second electron reflecting layer 18, and the third electron reflecting layer 19 are laminated in this order on the highly conductive layer 16. Here, the relationship between the first electron reflecting layer 17 and the second electron reflecting layer 18 is the same as that described above with reference to FIG. That is, the first electron reflecting layer 17 is formed as an oxide of an element that is more easily oxidized.

  On the other hand, the third electron reflecting layer 19 may be formed of an oxide of an element that is more easily oxidized than the second electron reflecting layer 18, and conversely, than the second electron reflecting layer 18, You may form with the oxide of the element which is harder to oxidize.

  When the third electron reflecting layer 19 is formed of an element that is easily oxidized, the third electron reflecting layer 19 itself becomes a stable oxide, and oxygen outflow from the third electron reflecting layer 19 to the protective layer 20 is suppressed. be able to. As a result, the lower first and second electron reflecting layers 17 and 18 can also act as an oxygen diffusion barrier.

  On the other hand, when the third electron reflecting layer 19 is formed of an element that is difficult to oxidize, oxygen easily flows out from the electron reflecting layer 19 to the protective layer 20. However, similar to the mechanism described above with reference to FIG. 2, the first and second electron reflecting layers 17 and 18 contain elements that are more easily oxidized. Oxygen outflow to the third electron reflecting layer 19 is less likely to occur. That is, the third electron reflecting layer 19 can act as an oxygen diffusion barrier with respect to the first and second electron reflecting layers 17 and 18.

  Although FIG. 3 illustrates the case where the electron reflecting layer has a three-layer structure, the present invention includes a structure in which the electron reflecting layer has a multilayer structure of four layers or more. In any of these cases, the relationship described above with reference to FIG. 2 may be maintained between the electron reflecting layer closest to the free layer 15 and the electron reflecting layer adjacent thereto.

  As described above, according to this embodiment, the electron reflecting layer on the free layer has a multilayer structure, and the electron reflecting layer closest to the free layer is oxidized with an element that is more easily oxidized than the electron reflecting layer adjacent thereto. By forming with an object, stable electron reflection characteristics can be realized.

(Third embodiment)
FIG. 4 is a conceptual diagram showing the cross-sectional configuration of the main part of the magnetic head of the present invention. That is, the alumina gap layer 102 is formed on the substrate 101, and the magnetoresistive effect element SV of the present invention is selectively provided thereon. As the magnetoresistive effect element SV, any of the elements described above with reference to the first to second embodiments is used. A pair of bias layers 103 and 103 are provided at both ends of the magnetoresistive effect element SV in order to bias the magnetization of the free layer. The bias layer 103 is made of a ferromagnetic material or an antiferromagnetic material.

  Further, a pair of electrodes 104 and 104 for supplying a sense current are provided at both ends of the magnetoresistive effect element SV, and an alumina gap layer 105 and a head protection film 106 are formed thereon.

  Here, the distance between the shields can be about 50 nm to 100 nm, and the track width can be about 0.15 to 0.3 microns.

(Example)
Examples of the present invention will be described below.

An SV film having the following configuration was prepared by sputtering, and the MR characteristics were compared.

Ta3nm (underlayer) / NiFeCr3nm (underlayer) /
PtMn 10 nm (antiferromagnetic layer) / CoFe 1.5 nm (pinned layer) /
Ru 0.9 nm (pinned layer) / CoFe 0.5 nm (pinned layer) /
Fe oxide 1.5 nm (electron reflecting layer) / CoFe 2 nm (pinned layer) /
Cu 2 nm (nonmagnetic intermediate layer) / CoFe 2 nm (free layer) /
Cu 1 nm (highly conductive layer) / X (electron reflective layer) /
Amorphous alumina 100nm

The SV film is oxidized by various oxidation methods to form a 1 nm thick Fe oxide or Cr oxide as the electron reflection layer X, and the product of EXAFS (Extended X-ray Absoption Fine Structure) is formed. The types and their abundance ratios and the crystallinity were observed by cross-sectional TEM. The results are summarized below.

Sample X Oxidation method Composition
(Thickness 1nm) (After heat treatment in vacuum at 270 ℃ for 10 hours)

Example 1 Fe oxide Oxygen ion irradiation 30 seconds FeO: Fe2O3: Fe3O4
= 0.5: 8.5: 1.5
Example 2 Fe oxide Oxygen radical irradiation 30 seconds FeO: Fe2O3: Fe3O4
= 0.5: 8.5: 1.5
Example 3 Ion beam sputtering of Fe oxide Fe2O3 FeO: Fe2O3: Fe3O4
= 0.5: 8.5: 1.5
Example 4 Cr oxide Oxygen ion irradiation 30 seconds Cr: Cr2O3 = 0: 10
Example 5 Cr oxide Oxygen radical irradiation 30 seconds Cr: Cr2O3 = 0: 10

Comparative Example 1 Fe oxide Natural oxidation FeO: Fe2O3: Fe3O4
= 5: 1: 4
Comparative Example 2 Fe oxide Oxygen ion irradiation 15 seconds FeO: Fe2O3: Fe3O4
= 0.5: 1.5: 8.5
Comparative Example 3 Cr oxide Natural oxidation Cr: Cr2O3 = 0.5: 9.5

Here, in Examples 1 and 2 and Comparative Examples 1 and 2, when forming the Fe material of the electron reflecting layer X, first, metal Fe was formed to a thickness of 1 nm, and then an oxidation treatment was performed.

In the case of natural oxidation, the oxidation treatment was performed in an atmosphere of the order of 10 ⁻⁶ Torr. In the case of ion irradiation, 1 sccm of Ar (argon) and 5 sccm of O ₂ (oxygen) were introduced into plasma, and the acceleration voltage was 50 eV.

Oxygen radical irradiation was performed by introducing 1 sccm of Ar and 5 sccm of O ₂ into plasma, and introduced by a differential pressure from an irradiation port separated from the substrate by 10 to 15 cm.

In the ion beam sputtering, an Fe ₂ O ₃ target was sputtered with Ar. Also, 1 sccm of oxygen was mixed with Ar.

The results of evaluating the MR characteristics of these samples are summarized below.

Sample After annealing at 270 ° C for 10 hours After 270 ° C for 30 hours

Example 1 16% 16.1%
Example 2 15.8% 16%
Example 3 15.7 16%
Example 4 16.5% 16.5%
Example 5 16.3% 16.4%
Comparative Example 1 12% 10%
Comparative Example 2 15% 14%
Comparative Example 3 13.5% 14%

While Comparative Example 1 was only 12%, Comparative Example 2 and Examples 1 to 3 showed large values of 15% or more. This is considered to be because, in Comparative Example 1, various phases of Fe oxide are mixed, and the electron potential varies, so that good electron reflection cannot be obtained. Even in the cross-sectional TEM, the comparative example 1 was observed in an amorphous form everywhere, while in the comparative examples 2 and 1-3, it was observed that the oxide layer itself was epitaxially grown. As described above, it was found that the oxide forms a clear crystal lattice by performing the oxidation treatment with energy. It was also found that this improves the MR.

On the other hand, when the magnetization measurement of Comparative Example 2 was attempted, a clear difference in spontaneous magnetization was observed compared to the Example, and the difference was 5% of the total magnetization. From this, it was found that the bias point is shifted. This is because a large amount of Fe ₃ O ₄ which is a ferrimagnetic component is contained.

On the other hand, in the example, as a result of the magnetization measurement, no significant difference was observed from the case where no Fe oxide was formed. Therefore, it was possible to adjust the bias point according to the thickness design. In addition, Cr ₂ O ₃ is an antiferromagnetic material. In this case, too, in the case of natural oxidation, a mixed state with a metal phase is formed, and the crystal lattice image contains a lot of amorphous components. It was found that the electron reflection effect was slightly suppressed.

  On the other hand, with oxygen radical irradiation and ion irradiation, it was found that the film had good crystallinity even in cross-sectional TEM. Good MR characteristics were also obtained. Further, all the corundum oxides of alloys selected from Co, Fe, Ni and Cr showed good MR characteristics. Further, those obtained by adding 5% or less of Si, Mg, Al, B, etc. also showed good MR characteristics and heat resistance.

Next, the following structure was created as a configuration of X.

Sample composition

Example 6 Ta oxide 2 nm / NiO 2 nm / Ta 3 nm
Example 7 Ta oxide 2 nm / Al ₂ O ₃ 2 nm / Ta ₃ nm
Example 8 Ta oxide 2 nm / NiO 2 nm
Example 9 Ta oxide 2 nm / Al ₂ O ₃ 2 nm

Comparative Example 4 Ta oxide 2 nm / 3Ta
Comparative Example 5 Ta oxide 2 nm
Comparative Example 6 NiO 2 nm / Ta oxide 2 nm / Ta 3 nm
Comparative Example 7 Al ₂ O ₃ 2 nm / Ta oxide 2 nm / Ta ₃ nm
Comparative Example 8 NiO 2 nm / Ta oxide 2 nm
Comparative Example 9 Al ₂ O ₃ 2 nm / Ta oxide 2 nm

All the oxide layers were formed by forming a metal layer and oxidizing it by ion beam irradiation. The results of these MR measurements are shown below.

Sample After annealing at 270 ° C for 10 hours After 270 ° C for 30 hours

Example 6 15% 14.9%
Example 7 15.1% 14.9%
Example 8 15.3% 15.3%
Example 9 15.3% 15.2%

Comparative Example 4 11% 9.8%
Comparative Example 5 14.2% 11.9%
Comparative Example 6 11.1% 10%
Comparative Example 7 14.3% 13%
Comparative Example 8 11.4% 10.1%
Comparative Example 9 14.8% 13.5%

In Comparative Example 4, the MR of both types of annealing is 4-5% smaller than that of the Example, because the oxygen in the Ta oxide layer easily diffuses into the protective film Ta, which is the same kind of metal. This is because oxygen deficient portions or metal Ta is deposited at the interface with the Cu layer (highly conductive layer).

EDX observation revealed that oxygen was greatly reduced after annealing from the interface. On the other hand, in Examples 6 and 7, MR is about 15%, and the heat resistance is greatly improved. This is because NiO, Al ₂ O _{3 and the} like function as an oxygen diffusion barrier. EDX observation showed that the interface oxygen did not change before and after annealing.

  In Comparative Example 5, the layer X is an amorphous Ta oxide, so that it exhibits good characteristics when annealed for a short time. However, oxygen is transferred to and from amorphous alumina because it is amorphous when heat-resistant for a long time. Therefore, the electron potential at the Ta oxide interface changes and the characteristics deteriorate.

  In Comparative Examples 6 and 8, since NiO was formed at the interface, good electron reflection characteristics could not be obtained. It was difficult to obtain good film quality with NiO having a film thickness of about 2-5 nm, and it was confirmed in this example that it was growing in an island shape at the interface with Cu.

  Comparative Examples 7 and 9 show good characteristics when annealed for a short time, and retain some characteristics even when annealed for a long time. However, the characteristics are slightly inferior to those of Examples 7 and 9. This is because even in Comparative Examples 7 and 9, the diffusion of oxygen is suppressed as a whole by laminating the oxide layer, but since Ta has a higher binding energy to oxygen than Al, some oxygen is oxidized by Ta. This is thought to be caused by the fact that the interface state has been changed by being sucked into the object.

  In all of these comparative examples, it was found that diffusion of metal atoms occurred between the oxide layers or between the oxide and the protective film or the insulating film amorphous alumina by annealing at 270 ° C. for 50 hours. . On the other hand, in all the examples, there was no significant change in the characteristics even after the similar annealing, and it was found that there was no problem if the diffusion was about 2-3%.

  Moreover, those obtained by adding 5% or less of Si, Mg, Al, B, etc. to these oxides also showed good heat resistance. In particular, in the oxide in contact with the Cu layer, as a result of analysis by EDX, it was found that the diffusion of oxygen to the oxide layer laminated on the outer side was further suppressed.

  As described above, it has been found that a structure in which layers having different binding energies with oxygen are stacked efficiently suppresses oxygen diffusion.

  The magnetoresistive element and the magnetic head of the present invention have been described above with reference to specific examples.

  Next, the magnetic reproducing apparatus of the present invention will be described. The magnetoresistive effect element and the magnetic head of the present invention described above can be incorporated into a magnetic head assembly integrated with a recording / reproducing apparatus and mounted on a magnetic reproducing apparatus, for example.

  FIG. 5 is a perspective view of a main part illustrating the schematic configuration of such a magnetic recording / reproducing apparatus. That is, the magnetic recording / reproducing apparatus 150 of the present invention is an apparatus using a rotary actuator. In the figure, a magnetic disk 200 for longitudinal recording or perpendicular recording is mounted on a spindle 152 and 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). In the magnetic disk 200, a head slider 153 that records and reproduces information stored in the magnetic disk 200 is attached to the tip of a thin film suspension 154. Here, the head slider 153 has, for example, a magnetic head using any one of the above-described magnetoresistive elements mounted near the tip thereof.

  When the magnetic disk 200 rotates, the medium facing surface (ABS) of the head slider 153 is held with a predetermined flying height from the surface of the magnetic disk 200.

  The suspension 154 is connected to one end of an actuator arm 155 having a bobbin portion for holding a drive coil (not shown). A voice coil motor 156, which is a kind of linear motor, is provided at the other end of the actuator arm 155. The voice coil motor 156 is composed of a drive coil (not shown) wound around the bobbin portion of the actuator arm 155, and a magnetic circuit composed of a permanent magnet and a counter yoke arranged so as to sandwich the coil.

  The actuator arm 155 is held by ball bearings (not shown) provided at two locations above and below the fixed shaft 157, and can be freely rotated and slid by a voice coil motor 156.

  FIG. 6 is an enlarged perspective view of the magnetic head assembly ahead of the actuator arm 155 as viewed from the disk side. That is, the magnetic head assembly 160 has an actuator arm 151 having, for example, a bobbin portion that holds a drive coil, and a suspension 154 is connected to one end of the actuator arm 155.

  A head slider 153 is attached to the tip of the suspension 154, and a reproducing magnetic head using any one of the magnetoresistive elements described above is mounted on the tip. A recording head may be combined. The suspension 154 has a lead wire 164 for writing and reading signals, and the lead wire 164 and each electrode of the magnetic head incorporated in the head slider 153 are electrically connected. In the figure, reference numeral 165 denotes an electrode pad of the magnetic head assembly 160.

  Here, a predetermined flying height is set between the medium facing surface (ABS) of the head slider 153 and the surface of the magnetic disk 200. The magnetic reproducing apparatus of the present invention may be a “floating traveling type” which operates in a state where the slider 153 floats a predetermined distance from the surface of the magnetic disk 200. The slider 153 and the magnetic disk 200 are positively contacted in reverse. Further, the “contact traveling type” for traveling may be used.

  The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples.

  For example, the magnetoresistive effect element of the present invention is not limited to those illustrated in FIGS. 1 to 3, and the layer configuration, the thickness and material of each layer are appropriately selected by those skilled in the art, and are the same as those of the present invention. The effect can be obtained similarly. Further, regarding the material constituting each layer, the elements of the layer are adjacent to each other depending on the temperature, ambient gas, etc. of the atmosphere in which the element is introduced during the process of the process during or after the element deposition. It is also possible to diffuse into other layers. Even if such diffusion occurs, it can be said that this is within the scope of the present invention if the entire structure of the present invention can be substantially confirmed in the finally obtained device.

  Further, the material and shape of each element constituting the magnetic head are not limited to those described above as specific examples, and the same effects can be obtained by using all the ranges that can be selected by those skilled in the art.

  In addition, the magnetic reproducing apparatus may perform only reproduction or may perform recording / reproduction, and the medium is not limited to the hard disk, and any other medium such as a flexible disk or a magnetic card may be used. A magnetic recording medium can be used. Further, a so-called “removable” type device in which the magnetic recording medium is removable from the device may be used.

It is a conceptual diagram showing the principal part cross-section structure of the magnetoresistive effect element concerning the 1st Embodiment of this invention. It is a conceptual diagram showing the principal part cross-section structure of the magnetoresistive effect element concerning the 2nd Embodiment of this invention. It is the conceptual diagram which illustrated the structure at the time of making an electron reflection layer into 3 layer structure. It is a conceptual diagram showing principal part sectional structure of the magnetic head of this invention. It is a principal part perspective view which illustrates schematic structure of the magnetic recording / reproducing apparatus by this invention. 5 is an enlarged perspective view of the magnetic head assembly ahead of the actuator arm 155 as viewed from the disk side. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Underlayer 12 Antiferromagnetic layer 13 Pin layer 14 Nonmagnetic intermediate layer 15 Free layer 16 High conductive layer 17 First electron reflecting layer 1 8 Second electron reflecting layer 19 Third electron reflecting layer 20 Protective layer 150 Magnetic Recording device 151 Magnetic disk 153 Head slider 154 Suspension 155 Actuator arm 156 Voice coil motor 157 Fixed shaft

Claims (7)

A magnetization pinned layer having a ferromagnetic film in which the magnetization direction is substantially pinned in one direction;
A magnetization free layer having a ferromagnetic film whose magnetization direction changes according to an external magnetic field;
A nonmagnetic intermediate layer provided between the magnetization pinned layer and the magnetization free layer;
With
On the side opposite to the nonmagnetic intermediate layer as viewed from the magnetization free layer, a highly conductive layer having higher conductivity than the magnetization pinned layer and the magnetization free layer is laminated,
A magnetic layer comprising a layer formed by irradiating an ionized gas with an oxide of an element different from a main element constituting the high conductive layer as a main component. Resistive effect element. A magnetization pinned layer having a ferromagnetic film in which the magnetization direction is substantially pinned in one direction;
A magnetization free layer having a ferromagnetic film whose magnetization direction changes according to an external magnetic field;
A nonmagnetic intermediate layer provided between the magnetization pinned layer and the magnetization free layer;
With
On the side opposite to the nonmagnetic intermediate layer as viewed from the magnetization free layer, a highly conductive layer having higher conductivity than the magnetization pinned layer and the magnetization free layer is laminated,
The highly conductive layer is formed by laminating a layer formed by irradiating a plasma gas with an oxide of an element different from the main element constituting the highly conductive layer as a main component. Magnetoresistive effect element.   A magnetic head comprising the magnetoresistive effect element according to claim 1.   A magnetic reproducing apparatus comprising the magnetic head according to claim 3 and capable of reading magnetic information stored in a magnetic recording medium. Sequentially stacking a first magnetic layer, a nonmagnetic intermediate layer, and a second magnetic layer;
Forming a highly conductive layer having higher conductivity than the first and second magnetic layers on the second magnetic layer;
Forming a layer mainly composed of an oxide of an element different from the main element constituting the highly conductive layer on the highly conductive layer;
A method of manufacturing a magnetoresistive effect element comprising:   6. The method of manufacturing a magnetoresistive effect element according to claim 5, wherein the oxide-based layer is formed by irradiating the highly conductive layer with ionized gas.   6. The method of manufacturing a magnetoresistive effect element according to claim 5, wherein the oxide-based layer is formed by irradiating the highly conductive layer with a plasma gas.

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