JP2012199496A - Spin conduction element and magnetic head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spin conduction element with improved spin injection efficiency, and a magnetic head.SOLUTION: The inventors have found a new magnetic sensor 1 which comprises a channel layer 10 constituted of Si, ferromagnetic layers 20A and 20B formed on the channel layer 10, and tunnel layers 22A and 22B formed so as to be interposed between the channel layer 10 and the ferromagnetic layers 20A and 20B, and for which the tunnel layers 22A and 22B are constituted of an alkali earth oxide of NaCl structure (BaO, for instance) and a part of alkali earth ions (Ba ions, for instance) of the alkali earth oxide is replaced with a different kind of alkali earth ions (Mg ions, for instance).

Description

  The present invention relates to a spin transport element and a magnetic head.

  Recently, the phenomenon of spin conduction in semiconductors has attracted much attention. In particular, silicon is a material that is the center of today's main semiconductor products. If silicon-based spintronics can be realized, new functions can be added to silicon devices without abandoning existing technologies.

  For example, there is a spin-MOSFET disclosed in Patent Document 1 below. Recently, in the following Non-Patent Document 1, the spin conduction phenomenon in silicon at room temperature has been proved, and movement toward application has begun. One of the reasons why the spin conduction phenomenon at room temperature has not been observed until recently is one of the causes that the temperature dependence of the spin injection efficiency into silicon rapidly decreases with increasing temperature (the following non-patent document) 2 and 3). Furthermore, there is a problem of output necessary for application. As shown in the following Patent Documents 1 to 7, the voltage generated by spin accumulation and conduction is 1 mV or less even at a low temperature, and the output needs to be improved in the future for practical application products. .

Note that Al ₂ O ₃ (Non-Patent Document 4), SiO ₂ (Non-Patent Document 5), MgO (Non-Patent Document 6) are used as tunnel layer materials (tunnel materials) formed on the silicon channel layer for spin injection. ) Have been conventionally known, and all are representative substances in spintronics.

JP 2004-111904 A

T. Suzuki et.al., Applied Physics Express 4 (2011), 023003 T. Sasaki et.al., Applied Physics Letter 96 (2010), 122101 T. Sasaki et.al., Applied Physics Letter 98 (2011), 012508 Erveet.al., Applied Physics Letter 91 (2007), 212109 C. H.Li et.al., Applied Physics Letter 95 (2009), 172102 T. Sasaki et.al., Applied Physics Express 2 (2009), 053003 F. J. Jedema Nature London 416 (2002), 713

  Any of the tunnel materials described above is in a stable amorphous state, but it is difficult to epitaxially grow on silicon because the lattice constant is 9% or more different from that of silicon of the channel layer material (channel material) or an amorphous film. Even if epitaxial growth can be realized, since the difference in lattice constant is large, it is necessary to form a metastable state by forming a lattice mismatch near the growth interface. In such a case, there is a possibility that spins are scattered at a portion where lattice mismatch occurs, and spin injection is not efficiently performed.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a spin transport element and a magnetic head with improved spin injection efficiency.

  In order to improve the spin injection efficiency, the inventors focused on the difference in lattice constant between the channel material and the tunnel material. In order to remove the lattice mismatch due to the difference in lattice constant, it is necessary to select a tunnel material having a lattice constant close to that of the channel material. In order to further eliminate the lattice mismatch, it is conceivable that the ions in the tunnel material having a lattice constant close to that of the channel material are partially replaced with ions having different ion radii to make the channel material closer to the lattice constant.

  Therefore, the inventors include a channel layer made of Si, a ferromagnetic layer stacked on the channel layer, and a tunnel layer formed so as to be interposed between the channel layer and the ferromagnetic layer. And the tunnel layer is made of an alkaline earth oxide having a NaCl structure, and a part of the alkaline earth ions of the alkaline earth oxide is replaced with a different kind of alkaline earth ion. I found a new element.

  In this spin transport device, even if the alkaline earth ions of the alkaline earth oxide of the NaCl structure constituting the tunnel layer are replaced with different types of alkaline earth ions, the NaCl structure is maintained, and only the lattice constant is obtained. Change. Therefore, by replacing the alkaline earth ions of the alkaline earth oxide constituting the tunnel layer with a predetermined alkaline earth ion so as to approach the lattice constant of Si of the channel material, a gap between the channel material and the tunnel material is obtained. The lattice mismatch is significantly relaxed, and the spin injection efficiency in the spin transport device is improved.

  Moreover, the aspect by which the tunnel layer is comprised by MgO or BaO may be sufficient.

  Further, the tunnel layer may be composed of MgO, and Mg ions in the tunnel layer may be replaced with Be ions at a rate of 1 to 6 atomic percent. The tunnel layer is composed of BaO, and the tunnel layer The embodiment may be such that the Ba ions therein are substituted with Mg ions at a rate of 1 to 7 atomic percent.

  Here, MgO and BaO are alkaline earth oxides having the same NaCl structure, and the lattice constants are 4.313Å (MgO) and 5.526Å (BaO), respectively. When the crystal axis orientation of MgO is rotated 45 degrees, it becomes 5.958 Å, which is about 10% different from the lattice constant of 5.4309 シ リ コ ン of silicon. Therefore, when the tunnel material is MgO, the lattice constant of the tunnel material approaches that of the channel material silicon by replacing some Mg ions with Be ions having a smaller ion radius. Similarly, when the tunnel material is BaO, the lattice constant of the tunnel material approaches that of the channel material silicon by replacing some of the Ba ions with Mg ions having a smaller ion radius.

  Further, at least a part of the interface between the channel layer and the tunnel layer may be lattice-matched.

  Furthermore, the aspect whose film thickness of a tunnel layer is 1.0-2.5 nm may be sufficient.

  In addition, the ferromagnetic layer may have a single magnetic domain. The ferromagnetic layer may have a magnetization direction fixed by shape anisotropy or a magnetization direction fixed by an antiferromagnetic film. In other words, the orientation of magnetization may be fixed by a synthetic film.

  The spin transport device of the present invention can be applied to a magnetic head, a spin transistor, a memory, a sensor, a logic circuit, and the like.

  According to the present invention, a spin transport element and a magnetic head with improved spin injection efficiency are provided.

FIG. 1 is a schematic cross-sectional view of a magnetic sensor according to an embodiment of the present invention. FIG. 2 is a partial enlarged view of an electrode portion of the magnetic sensor shown in FIG. FIG. 3 is a graph showing the Hanle effect of the magnetic sensor when MgO is used as the tunnel material. FIG. 4 is a graph showing the Hanle effect of the magnetic sensor when BaO is adopted as the tunnel material. FIG. 5 is a graph showing changes in the lattice constant and the output when the BaO tunnel material is replaced with Mg ions. FIG. 6 is a graph showing changes in the lattice constant and output when the MgO tunnel material is replaced with Be ions. FIG. 7 is a schematic cross-sectional view of a magnetic sensor having a mode different from that of FIG. FIG. 8 is a schematic sectional view showing a magnetic head including the magnetic sensor shown in FIG. FIG. 9 is a partially enlarged view of an electrode portion having a mode different from that in FIG.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  As shown in FIG. 1, a magnetic sensor 1 that is one of the spin transport elements includes a channel layer 10, a first ferromagnetic layer 20A, and a second ferromagnetic layer 20B, and an external magnetic field in the Z-axis direction. Is detected.

The channel layer 10 extends from the first ferromagnetic layer 20 </ b> A to the second ferromagnetic layer 20 </ b> B, and has a rectangular shape when viewed from the thickness direction of the channel layer 10. The current and spin current flowing in the channel layer 10 are structured to flow mainly in the X-axis direction. The channel layer 10 may be doped with ions for imparting conductivity. The ion concentration can be, for example, 1.0 × 10 ^{15 to} 1.0 × 10 ²² cm ⁻³ . The channel layer 10 is preferably a material having a long spin lifetime, and is made of Si. In addition, the distance from the first ferromagnetic layer 20 </ b> A to the second ferromagnetic layer 20 </ b> B in the channel layer 10 is preferably equal to or shorter than the spin diffusion length of the channel layer 10.

  The first ferromagnetic layer 20 </ b> A and the second ferromagnetic layer 20 </ b> B function as injection electrodes for injecting spins into the channel layer 10 or reception electrodes for detecting spins conducted through the channel layer 10. The first ferromagnetic layer 20 </ b> A is provided on the first region 11 of the channel layer 10. The second ferromagnetic layer 20 </ b> B is provided on the second region 12 of the channel layer 10.

  Each of the first ferromagnetic layer 20A and the second ferromagnetic layer 20B has a rectangular parallelepiped shape with the Y axis direction as the major axis, and the difference in the reversal magnetic field is caused by the difference in the aspect ratio between the Y axis direction and the X axis direction. I'm wearing it. The first ferromagnetic layer 20A and the second ferromagnetic layer 20B can have the same width in the Y-axis direction, and the first ferromagnetic layer 20A and the second ferromagnetic layer 20B can have different widths in the X-axis direction. The coercive force can be made different. As shown in FIG. 1, the magnetization direction G1 of the first ferromagnetic layer 20A can be the same as the magnetization direction G2 of the second ferromagnetic layer 20B, for example. In this case, the magnetization of the first ferromagnetic layer 20A and the second ferromagnetic layer 20B can be easily fixed.

  The first ferromagnetic layer 20A and the second ferromagnetic layer 20B are made of a ferromagnetic material. The material of the first ferromagnetic layer 20A and the second ferromagnetic layer 20B is, for example, TbFeCo, FePt, CoPt, FePd, MnAl, CrCo, and other materials include Al, Cr, Mn, Co, Fe, Ni, A metal selected from the group consisting of Pd, Pt, Tb, an alloy containing one or more elements of the group, or a group consisting of one or more elements selected from the group and B, C, N, Si, Ge It can be set as the compound containing 1 or more elements selected from these.

  The magnetic sensor 1 further includes a first reference electrode 30A and a second reference electrode 30B. The first reference electrode 30 </ b> A is provided on the third region 13 of the channel layer 10. The second reference electrode 30 </ b> B is provided on the fourth region 14 of the channel layer 10. The channel layer 10 extends from the first ferromagnetic layer 20A to the first reference electrode 30A in a direction different from the direction extending from the first ferromagnetic layer 20A to the second ferromagnetic layer 20B. The second ferromagnetic layer 20B extends from the second ferromagnetic layer 20B to the second reference electrode 30B in a direction different from the direction extending from the second ferromagnetic layer 20B to the first ferromagnetic layer 20A. The first reference electrode 30A and the second reference electrode 30B are made of a conductive material, for example, a non-magnetic metal having a low resistance to Si such as Al.

  Between the third region 13 and the fourth region 14, the first region 11 and the second region 12 exist. On the channel layer 10, the first reference electrode 30A, the first ferromagnetic layer 20A, the second ferromagnetic layer 20B, and the second reference electrode 30B are arranged in this order at a predetermined interval in the X-axis direction. ing.

  The magnetic sensor 1 further includes tunnel layers 22A and 22B. The tunnel layers 22A and 22B are provided between the channel layer 10 and the first and second ferromagnetic layers 20A and 20B, respectively. As a result, spin-polarized electrons can be injected from the first ferromagnetic layer 20A and the second ferromagnetic layer 20B to the channel layer 10 with high efficiency, and the potential output of the magnetic sensor 1 can be increased. .

  The tunnel layers 22A and 22B are tunnel barriers made of an insulating material film, and are made of BaMgO in which Ba ions of BaO, which is an alkaline earth oxide having a NaCl structure, are partially substituted with Mg ions. The thickness of the tunnel layers 22A and 22B is preferably 2.5 nm or less from the viewpoint of suppressing an increase in resistance and functioning as a tunnel insulating layer, and is 1.0 nm or more, which is a thickness at which BaMgO can be formed as a film. Preferably there is.

  The magnetic sensor 1 further includes an insulating film (or an insulator). The insulating film has a function of preventing the channel layer 10 from being exposed and electrically and magnetically insulating the channel layer 10. The insulating film preferably covers a necessary region of the surface (for example, the lower surface, the side surface, or the upper surface) of the channel layer 10. The insulating film 10 a is provided on the lower surface of the channel layer 10, and the insulating film 10 b is provided on the upper surface of the channel layer 10.

  Specifically, the insulating film 10 b exists between the upper surface of the region existing between the first region 11 and the second region 12 of the channel layer 10 and between the first region 11 and the third region 13 of the channel layer 10. Provided on the upper surface of the region that is between the second region 12 and the fourth region 14. If a wiring connected to the first reference electrode 30A, the first ferromagnetic layer 20A, the second ferromagnetic layer 20B, and the second reference electrode 30B is provided on the insulating film 10b, the spin of the channel layer 10 is formed by this wiring. Can be prevented from being absorbed. In addition, by providing a wiring on the insulating film 10b, it is possible to suppress a current from flowing from the wiring to the channel layer 10.

  Next, an example of the procedure for manufacturing the magnetic sensor 1 will be described.

  First, alignment marks are formed on a previously prepared SOI substrate (Si 100 nm / SiO x 200 nm / Si substrate). Using the alignment mark as a mark, the insulating film 10a is formed on the substrate by, for example, molecular beam epitaxy (MBE).

  Subsequently, the channel layer 10 is formed on the insulating film 10a by, for example, the MBE method. Ions for imparting conductivity are implanted into the channel layer 10 to adjust the conduction characteristics of the channel layer 10. Thereafter, ions are diffused by thermal annealing at a temperature of 900 ° C. Next, deposits, organic substances, and oxide films on the surface of the channel layer 10 were removed by RCA cleaning, and then the surface was terminated with hydrogen using an HF cleaning solution.

Thereafter, the substrate was carried into an MBE apparatus (base vacuum degree: 2.0 × 10 ⁻⁹ Torr or less), and then hydrogen on the substrate surface was desorbed by a flushing process by heating the substrate to form a clean surface. The degree of vacuum at the time of deposition is 5 × 10 ⁻⁸ Torr or less, and BaMgO (film thickness 1.2 nm), Fe (film thickness 10 nm), Ru (film thickness 1.5 nm), Ta (film thickness 1 nm) are formed in this order. Do the membrane. That is, on the channel layer 10, a BaMgO film to be the tunnel layers 22A and 22B and an Fe film (ferromagnetic film) to be the first ferromagnetic layer 20A and the second ferromagnetic layer 20B are formed in this order. As a result, at least a part of the interface between the channel layer 10 and the tunnel layers 22A and 22B is lattice-matched.

  Next, the BaMgO film and the ferromagnetic film are processed using a mask by, for example, an electron beam (EB) method. For example, as disclosed in JP 2010-199320 A, the channel layer 10 is formed by ion milling or chemical etching using a mask. Further, a BaMgO film and a ferromagnetic film on the channel layer 10 are formed by, for example, an electron beam (EB) method. By further ion milling or chemical etching, a first ferromagnetic layer 20A is formed on the first region 11 of the channel layer 10 via the tunnel layer 22A, and a tunnel is formed on the second region 12 of the channel layer 10. The second ferromagnetic layer 20B is formed via the layer 22B. As described above, if necessary, an antiferromagnetic layer may be further formed on the first ferromagnetic layer 20A and the second ferromagnetic layer 20B by, for example, the MBE method. Then, annealing is performed under a magnetic field in order to fix the magnetization direction of the first ferromagnetic layer 20A or the second ferromagnetic layer 20B. Thereafter, unnecessary tunnel films and ferromagnetic films formed on the channel layer 10 are removed by, for example, ion milling.

  Next, an insulating film 10b is formed on the channel layer 10 from which unnecessary barrier films and ferromagnetic films have been removed. Further, the insulating film 10b on the third region 13 and the fourth region 14 of the channel layer 10 is removed, and the first reference electrode 30A and the second reference electrode 30B are formed, respectively.

  Hereinafter, the function and effect of the magnetic sensor 1 will be described.

  First, the magnetization directions of the first ferromagnetic layer 20A and the second ferromagnetic layer 20B are fixed. In the example shown in FIG. 1, the magnetization direction G1 of the first ferromagnetic layer 20A is fixed in the same direction (Y-axis direction) as the magnetization direction G2 of the second ferromagnetic layer 20B.

  For example, by connecting the first ferromagnetic layer 20A and the first reference electrode 30A to a current source, a detection current can be passed through the first ferromagnetic layer 20A. When a current flows from the nonmagnetic channel layer 10 through the tunnel layer 22A to the first ferromagnetic layer 20A, which is a ferromagnetic material, spin in a direction corresponding to the magnetization direction G1 of the first ferromagnetic layer 20A is generated. The electrons they have are injected into the channel layer 10. The injected spin diffuses toward the second ferromagnetic layer 20B. In this way, the current and spin current flowing in the channel layer 20 can be configured to flow mainly in the X-axis direction.

  Here, when no external magnetic field is applied to the channel layer 10, that is, when the external magnetic field is zero, the direction of spins diffusing in the region between the first region 11 and the second region 12 of the channel layer 10 does not rotate. Accordingly, spins in the same direction as the magnetization direction G2 of the second ferromagnetic layer 20B set in advance diffuse to the second region 12. Therefore, when the external magnetic field is zero, the resistance output or voltage output becomes an extreme value. The maximum value or the minimum value can be taken depending on the direction of current or magnetization. The output can be evaluated by an output measuring instrument such as a voltage measuring instrument connected to the second ferromagnetic layer 20B and the second reference electrode 30B.

  On the other hand, consider a case where an external magnetic field is applied to the channel layer 10. In the example of FIG. 1, the external magnetic field is applied from the Z-axis direction. When an external magnetic field is applied, the direction of the spin diffused in the channel layer 10 rotates around the axial direction (Z-axis direction) of the external magnetic field (so-called Hanle effect). Depending on the relative angle between the rotation direction when the spin diffuses to the second region 12 of the channel layer 10 and the magnetization direction G2 of the second ferromagnetic layer 20B set in advance, that is, the spin, the channel layer 10 And the voltage output and resistance output at the interface of the second ferromagnetic layer 20B are determined. When an external magnetic field is applied, the direction of the spin diffusing through the channel layer 10 rotates, and thus the direction of magnetization G2 of the second ferromagnetic layer 20B is not aligned. Therefore, the resistance output or voltage output takes the maximum value when the external magnetic field is zero, becomes the maximum value or less when the external magnetic field is applied, and applies the external magnetic field when it takes the minimum value when the external magnetic field is zero. Then, it becomes the minimum value or more.

  Therefore, an output peak appears when the external magnetic field is zero, and when the external magnetic field is increased or decreased, the output decreases. That is, since the output changes depending on the presence or absence of an external magnetic field, the magnetic sensor 1 according to this embodiment can be used as a magnetic detection element.

  In the magnetic sensor 1, as described above, the external magnetic field is zero and the output peak appears. Therefore, for example, when the magnetic sensor 1 is applied to a magnetic head or the like and the positive / negative timing of the external magnetic field is read, an output peak appears at the zero point where the magnetic field of the domain wall cancels. . The magnetic sensor 1 is also characterized by no hysteresis.

  As described above, the tunnel layers 22A and 22B in the magnetic sensor 1 are composed of BaMgO, and it can be seen from the graphs of FIGS. 3 and 4 that the same Hanle results are obtained for both MgO and BaO.

The result of ICP emission analysis was used for the ratio of Ba and Mg (that is, composition ratio x). An evaluation Ba _1-X Mg _X O film (film thickness: 3 nm) was used.

FIG. 5 (a) is a graph showing changes in the lattice constant when Ba ions of the BaO tunnel material are partially substituted with Mg ions and the composition ratio of Ba _1-x Mg _x O is changed. From the graph, it can be seen that as the Mg composition ratio (x) is increased from 1 atomic percent to 7 atomic percent, it gradually approaches the lattice constant of 5.4309４ of silicon.

FIG. 5B is a graph showing changes in spin output when Ba ions of the BaO tunnel material are partially substituted with Mg ions and the composition ratio of Ba _1-x Mg _x O is changed. From the graph, it can be seen that as the Mg composition ratio (x) is increased from 1 atomic percent to 7 atomic percent, the spin output gradually increases.

  That is, from the graphs of FIGS. 5A and 5B, by replacing the Ba ions in the BaMgO tunnel material with Mg ions at a ratio of 1 to 7 atomic percent, the channel material silicon and the tunnel material BaMgO It is considered that the lattice mismatch is significantly relaxed, and the spin injection efficiency in the spin transport device is improved.

  In the graph of FIG. 5A, when the Mg composition ratio is 8 atomic percent or more, the change in the lattice constant is small, indicating that it is difficult to replace Mg. Also, the spin output tends to increase as the composition ratio of Mg increases, but tends to decrease when the composition ratio becomes 8 atomic percent or more. This is because when BaO is replaced with Mg and close to the lattice constant with Si, a factor of spin scattering due to the substitution also occurs at the same time, and when the Mg composition ratio increases, the output tends to decrease. When the Mg substitution amount is 8 atomic percent or less, the lattice constant changes linearly with respect to the substitution amount, but when it is 8 atomic percent or more, there is a tendency to deviate from the straight line. In the case of 8 atomic percent or more, Ba ions cannot be replaced with Mg ions, and conversely, there is a possibility that they function as spin scatterers as impurities.

In the embodiment described above, the tunnel material is Ba _1-x Mg _x O, and the result as shown in FIG. 5 is obtained. Even when the tunnel material is Mg _1-x Be _x O, as shown in FIG. Similar results are obtained.

FIG. 6A is a graph showing changes in the lattice constant when Mg ions of the MgO tunnel material are partially substituted with Be ions and the composition ratio of Mg _1-x Be _x O is changed. From the graph, when the composition ratio (x) of Be is increased from 1 atomic percent to 6 atomic percent, the lattice constant decreases linearly with respect to the substitution amount of Be. It can be seen that when the basic lattice of MgO is considered as the basic lattice when the lattice constant is decreased by 45 degrees, the lattice constant gradually approaches the lattice constant of 5.4309 格子 of silicon.

FIG. 6B is a graph showing changes in spin output when Mg ions of the MgO tunnel material are partially substituted with Be ions and the composition ratio of Mg _1-x Be _x O is changed. From the graph, it can be seen that as the composition ratio (x) of Be is increased from 1 atomic percent to 6 atomic percent, the spin output gradually increases.

  That is, from the graphs of FIGS. 6A and 6B, by replacing Mg ions in the MgBeO tunnel material with Be ions at a rate of 1 to 6 atomic percent, the channel material silicon and the tunnel material MgBeO It is considered that the lattice mismatch is significantly relaxed, and the spin injection efficiency in the spin transport device is improved.

  The magnetic sensor 1 of the present invention can be applied to a magnetic head 100A as shown in FIG. 8, a spin transistor, a memory, a sensor, a logic circuit, or the like. When optimizing the magnetic head, it is preferable that the external magnetic field is incident from the Y-axis direction of FIG. 1, and in this case, the ferromagnetic layers 20A and 20B are formed like the magnetic sensor 1A shown in FIG. It is fixed to the X axis (or Z axis). As a method for fixing the magnetization directions of the ferromagnetic layers 20A and 20B, an antiferromagnetic film that fixes the magnetization direction in the X direction or a perpendicular magnetization film having magnetic anisotropy in the Z direction is preferable.

  FIG. 8 is a schematic sectional view showing a magnetic head 100A which is a thin film magnetic recording / reproducing head. The magnetic sensor 1A shown in FIG. 7 described above can be applied to the read head unit 100a of the magnetic head 100A. The magnetic head 100 </ b> A performs magnetic information recording and reading operations at a position where its air bearing surface (air bearing surface) ABS is disposed to face the recording surface 120 a of the magnetic recording medium 120. The front end surface of the channel layer 10 of the magnetic sensor 1A described above (the front surface of the channel layer 10 in FIG. 7) is disposed so as to correspond to the air bearing surface ABS.

  The magnetic recording medium 120 includes a recording layer 120b having a recording surface 120a and a soft magnetic backing layer 120c laminated on the recording layer 120b, and the magnetic recording medium 120 is magnetic in the direction indicated by the Z-axis direction in FIG. Progress relative to the head 100A. The magnetic head 100 </ b> A includes a recording head unit 100 b that performs recording on the magnetic recording medium 120 in addition to the reading head unit 100 a that reads records from the magnetic recording medium 120. The read head unit 100a and the recording head unit 100b are provided on the substrate 101 and are covered with a nonmagnetic insulating layer such as alumina.

  As shown in FIG. 8, a recording head unit 100b for writing is provided on the reading head unit 100a. In the recording head portion 100b, a contact portion 132 and a main magnetic pole 133 are provided on the return yoke 130, and these form a magnetic flux path. A thin film coil 131 is provided so as to surround the contact portion 132. When a recording current is passed through the thin film coil 131, a magnetic flux is released from the tip of the main magnetic pole 133, and information is recorded on the recording layer 120b of the magnetic recording medium 120 such as a hard disk. Can be recorded. As described above, the magnetic head 100A capable of detecting a magnetic flux from a minute region such as a recording medium can be provided by using the magnetic sensor 1 of the present invention.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the electrode structure in the portions of the first ferromagnetic layer 20A and the second ferromagnetic layer 20B can be a laminated structure magnetized by a synthetic film as shown in FIG. 9 is a structure in which BaMgO (film thickness 1.2 nm), Fe (film thickness 10 nm), Ru (film thickness 1.5 nm), and Ta (film thickness 1 nm) are sequentially formed on Si. Corresponding to the channel layer 10, the tunnel layers 22 A and 22 B, the ferromagnetic layers 20 A and 20 B, the protective film layer 24, the Ru layer 26, and the ferromagnetic layer 28.

  The magnetization directions of the first ferromagnetic layer 20A and the second ferromagnetic layer 20B are fixed by an antiferromagnetic layer or shape anisotropy provided on the first ferromagnetic layer 20A and the second ferromagnetic layer 20B. May be. For example, in the first ferromagnetic layer 20A and the second ferromagnetic layer 20B, the difference in the reversal magnetic field is given by the difference in the aspect ratio between the X-axis direction and the Y-axis direction. Alternatively, the first ferromagnetic layer 20A and the second ferromagnetic layer 20B may be provided with an antiferromagnetic layer for fixing the magnetization direction. In this case, the first ferromagnetic layer 20A or the second ferromagnetic layer 20B having a higher coercive force in one direction than when no antiferromagnetic layer is provided can be obtained.

  In addition, it is preferable to substitute the ion which the tunnel material substitutes with the element of the same ion valence. Further, it is more preferable to substitute with an element having similar orbits of electrons that travel to the outermost shell. In the above-described embodiment, a method of partially replacing with Be, Mg, Ca, Sr, or Ba is preferable.

  DESCRIPTION OF SYMBOLS 1, 1A ... Magnetic sensor, 10 ... Channel layer, 20A, 20B ... Ferromagnetic layer, 22A, 22B ... Tunnel layer, 30A, 30B ... Reference electrode, 100A ... Magnetic head.

Claims (11)

A channel layer made of Si;
A ferromagnetic layer stacked on the channel layer;
A tunnel layer formed so as to be interposed between the channel layer and the ferromagnetic layer,
The tunnel layer is composed of an alkaline earth oxide having a NaCl structure, and a part of the alkaline earth ions of the alkaline earth oxide is replaced with a different kind of alkaline earth ion. Conductive element.   The spin transport device according to claim 1, wherein the tunnel layer is made of MgO or BaO.   The spin transport device according to claim 2, wherein the tunnel layer is made of MgO, and Mg ions in the tunnel layer are replaced with Be ions at a rate of 1 to 6 atomic percent.   The spin transport device according to claim 2, wherein the tunnel layer is made of BaO, and Ba ions in the tunnel layer are substituted with Mg ions at a rate of 1 to 7 atomic percent.   5. The spin transport device according to claim 1, wherein at least a part of an interface between the channel layer and the tunnel layer is lattice-matched.   The spin transport device according to claim 1, wherein the tunnel layer has a thickness of 1.0 to 2.5 nm.   The spin transport device according to any one of claims 1 to 6, wherein the ferromagnetic layer has a single domain.   The spin transport device according to claim 7, wherein the magnetization direction of the ferromagnetic layer is fixed by shape anisotropy.   The spin transport device according to claim 7, wherein the ferromagnetic layer is an antiferromagnetic film and the magnetization direction is fixed.   The spin transport device according to claim 7, wherein the ferromagnetic layer has a magnetization orientation fixed by a synthetic film.   A magnetic head comprising the spin transport device according to claim 1.

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