JP6969751B2 - Tunnel magnetoresistive element and magnetization direction correction circuit - Google Patents

Description

The present invention relates to a tunnel magnetoresistive element and a magnetization direction correction circuit.

The tunnel magnetoresistive element (TMR (Tunnel Magneto Resistive) element) is a fixed magnetic layer in which the direction of magnetization is fixed, a free magnetic layer in which the direction of magnetization changes under the influence of an external magnetic field, and a fixed magnetic layer. It has an insulating layer arranged between the free magnetic layer and the free magnetic layer, and forms a magnetic tunnel junction (MTJ). Examples of the one using this configuration include a magnetic memory, a magnetic head, a magnetic sensor, and the like (Patent Documents 1 and 2).
In addition, a soft magnetic layer (NiFe, CoFeSiB, etc.) that easily reacts to an external magnetic field is placed on the free magnetic layer, and a structure in which the free magnetic layer, the insulating layer, and the fixed magnetic layer are laminated in this order from the side closer to the substrate is formed. By heat treatment in a magnetic field, the resistance change of the insulating layer is utilized by the tunnel effect according to the angular difference between the direction of magnetization of the fixed magnetic layer and the direction of magnetization of the free magnetic layer caused by the magnetic field from the outside, and the high linearity is high. There is a technique for manufacturing a sensitive magnetic sensor (Patent Document 3).
A soft magnetic layer (NiFe, CoFeSiB, etc.) that easily reacts to an external magnetic field is arranged in the free magnetic layer, and a magnetic coupling layer (Ta) is further formed between the ferromagnetic layer and the soft magnetic layer bonded to the insulating layer. And Ru), a synthetic bond that generates only a magnetic bond is used while eliminating the bond between the magnetic tunnel bond and the soft magnetic material in terms of solid properties (Patent Documents 1-3).

Japanese Unexamined Patent Publication No. 9-25168 Japanese Unexamined Patent Publication No. 2012-221549 Japanese Unexamined Patent Publication No. 2013-105825 Japanese Patent No. 5897719 Japanese Patent No. 5259802 Japanese Patent No. 4970033

"1- and 2-Axis Magnetic Sensors HMC1001 / 1002/1021/1022" www.honeywell.com/magneticsensors Form # 900248 Rev C August 2008

When MTJ is used as a highly sensitive magnetic sensor, it is necessary to form a free magnetic layer using a soft magnetic material (NiFe, CoFeSiB, etc.) that is easily magnetized by an external magnetic field.
However, while the free magnetic layer improves the responsiveness to an external magnetic field, the characteristics of the magnetic material layer become unstable and the noise derived from the magnetic material increases, resulting in a good SN. You may not be able to get the ratio.
On the other hand, there is a technique of controlling the magnetization direction in a magnetic material mainly by using an anisotropic magnetoresistive element (AMR) (Patent Documents 4, 5 and 6). The purpose of this technique is to apply a pulsed magnetic field to a magnetoresistive element using a coil to forcibly align and stabilize the magnetization direction of the magnetic material in one direction.
However, since a coil is used, a magnetic field of only about 10 mT can be generated with a current of several amperes, and a fixed magnetic layer is formed using an antiferromagnetic material (Irmn, etc.), so that the magnetization direction is different. It is difficult to apply to MTJs that require a large magnetic field (generally several hundred mT) for inversion.

The present invention has been made in view of the above problems in the prior art, and an object of the present invention is to remove noise from the output of a tunnel magnetoresistive element by forcibly inverting the magnetization direction of the fixed magnetic layer. do.

The invention according to claim 1 for solving the above problems is an insulating layer between at least two or more ferromagnetic layers magnetized in a specific direction in which the direction of magnetization changes under the influence of an external magnetic field. Is a tunnel magnetoresistive element that forms a magnetic tunnel junction and changes the resistance of the insulating layer by a tunnel effect according to the relative angle of the magnetization direction of the ferromagnetic layer on both sides of the insulating layer.
Each of the ferromagnetic layers on both sides of the insulating layer has a composition and volume in which the direction of magnetization is reversed at a magnetic field strength of 1 μT or more and less than 10 mT.
The insulating layer and the ferromagnetic layers on both sides thereof are laminated in the order of the ferromagnetic layer on one side, the insulating layer, and the ferromagnetic layer on the other side from the side closer to the substrate.
The ferromagnetic layer on the other side is in contact with the ferromagnetic layer on the other side and the soft magnetic layer is laminated, so that the direction of magnetization is affected by the external magnetic field and the direction of magnetization is the ferromagnetic layer on the one side. It is a tunnel magnetic resistance element that functions as a free magnetic layer that is more variable.

The invention according to claim 2 is the tunnel magnetoresistive element according to claim 1, wherein the magnetization direction of the ferromagnetic layer on one side and the magnetization direction of the free magnetic layer are twisted positions.

The invention according to claim 3 comprises a bridge circuit in which at least one or more tunnel magnetoresistive elements according to claim 1 or 2 are mounted.
A set / reset circuit that alternately applies a set pulse magnetic field and a reset pulse magnetic field that invert the magnetization directions of the ferromagnetic layer to the tunnel magnetoresistive element of the bridge circuit.
It is a magnetization direction correction circuit including a detection circuit for detecting a signal output from the tunnel magnetoresistive element in synchronization with the alternating application of a set pulse magnetic field and a reset pulse magnetic field.

Fourth aspect of the present invention, by alternating application of the set pulse magnetic field and the reset pulse magnetic field, the one with reversing the magnetization direction of the side of the ferromagnetic layer, to claim 3 for reversing the magnetization direction of the free magnetic layer The magnetization direction correction circuit described.

According to the present invention, by forcibly inverting the magnetization direction of the fixed magnetic layer and the magnetization direction of the free magnetic layer, the signal component corresponding to the external magnetic field in the output of the tunnel magnetoresistive element is made independent of the noise component. The noise can be removed by inverting and separating the magnets.

A graph (column d) showing the ideal magnetoresistive characteristics to be realized by the present invention and a schematic diagram (column a) (column b) (column d) showing the direction of magnetization of the tunnel magnetoresistive element in each state on the graph. c). It is sectional drawing which shows the laminated structure of the tunnel magnetoresistive element of a conventional example. It is a graph which shows the magnetic resistance characteristic which appears in the conventional example of FIG. The horizontal axis is the external magnetic field (H (Oe)), and the vertical axis is the rate of change in the resistance of the tunnel magnetoresistive element (TMR ratio (%)). It is sectional drawing which shows the laminated structure of the tunnel magnetoresistive element of another conventional example. It is sectional drawing which shows the laminated structure of the tunnel magnetoresistive element which concerns on one comparative example of this invention. It is sectional drawing of the laminated structure which shows the manufacturing process of the tunnel magnetoresistive element of FIG. It is sectional drawing of the laminated structure which shows the manufacturing process of the tunnel magnetoresistive element of FIG. 5 following FIG. 6A. It is sectional drawing of the laminated structure which shows the manufacturing process of the tunnel magnetoresistive element of FIG. 5 following FIG. 6B. It is a graph which shows the magnetic resistance characteristic of the tunnel magnetoresistive element of FIG. The horizontal axis is the external magnetic field (H (Oe)), and the vertical axis is the rate of change in the resistance of the tunnel magnetoresistive element (TMR ratio (%)). It is a graph which shows the magnetoresistance characteristic of the tunnel magnetoresistive element of FIG. 5, and shows the thing after performing the 2nd and 3rd magnetic field heat treatment steps. The case where the heat treatment temperature of the second magnetic field heat treatment step is 200 ° C. and the heat treatment temperature of the third magnetic field heat treatment step is 180 ° C. is shown. The horizontal axis is the external magnetic field (H (Oe)), and the vertical axis is the rate of change in the resistance of the tunnel magnetoresistive element (TMR ratio (%)). It is a graph which shows the magnetoresistance characteristic of the tunnel magnetoresistive element of FIG. 5, and shows the thing after performing the 2nd and 3rd magnetic field heat treatment steps. The case where the heat treatment temperature of the second magnetic field heat treatment step is 200 ° C. and the heat treatment temperature of the third magnetic field heat treatment step is 200 ° C. is shown. The horizontal axis is the external magnetic field (H (Oe)), and the vertical axis is the rate of change in the resistance of the tunnel magnetoresistive element (TMR ratio (%)). It is a magnetization direction state diagram when a set magnetic field is applied to an AMR element. It is a magnetization direction state diagram when a reset magnetic field is applied to an AMR element. 4 is a phase diagram of the magnetization direction when a set magnetic field is applied to the tunnel magnetoresistive element of FIGS. 4 and 5. 4 is a phase diagram of the magnetization direction when a reset magnetic field is applied to the tunnel magnetoresistive element of FIGS. 4 and 5. It is sectional drawing which shows the laminated structure of the tunnel magnetoresistive element which concerns on one Embodiment of this invention. It is a magnetization direction state diagram when a set magnetic field is applied to the tunnel magnetoresistive element of FIG. 11 is a phase diagram of the magnetization direction when a reset magnetic field is applied to the tunnel magnetoresistive element of FIG. The outline of the signal processing by the detection circuit which concerns on one Embodiment of this invention is shown. It is a block diagram which shows the outline of the magnetization direction correction circuit which concerns on one Embodiment of this invention. It is a magnetization characteristic graph in the free magnetic layer of the tunnel magnetoresistive element which concerns on one Example of this invention. It is a magnetization characteristic graph in the fixed magnetic layer of the tunnel magnetoresistive element which concerns on one Example of this invention.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. The following is an embodiment of the present invention and does not limit the present invention.

First, the basic structure of the tunnel magnetoresistive element and the ideal magnetoresistive characteristics to be realized by the present invention will be described with reference to FIG.
As shown in FIG. 1, the tunnel magnetic resistance element 1 includes a fixed magnetic layer 10 in which the direction of magnetization is fixed, a free magnetic layer 30 in which the direction of magnetization changes under the influence of an external magnetic field, and a fixed magnetic layer. A magnetic tunnel junction is formed by the insulating layer 20 arranged between the 10 and the free magnetic layer 30, and the tunnel effect is applied according to the angular difference between the magnetization direction of the fixed magnetic layer 10 and the magnetization direction of the free magnetic layer 30. It changes the resistance of the insulating layer 20.
FIG. 1 (column a) (column b) (column c) shows the magnetization direction 10A of the fixed magnetic layer 10 and the magnetization direction 30A of the free magnetic layer 30 in each magnetic field state shown in FIG. 1 (column d).
FIG. 1 (column a) shows a state in which the detected magnetic field is zero (neutral position, position P0 on the graph in FIG. 1 (column d)), and FIG. 1 (column b) shows a state in which a predetermined positive magnetic field is applied (column a). The one at the position P1) on the graph of FIG. 1 (column d), and the one at the state where a predetermined negative magnetic field is applied (the position P2 on the graph of FIG. 1 (column d)) in FIG. 1 (column c). show.
In FIG. 1 (column a), in the state where the detected magnetic field is zero (neutral position P0), the magnetization direction 10A of the fixed magnetic layer 10 and the magnetization direction 30A of the free magnetic layer 30 are stable at a twisted position of approximately 90 degrees. doing. This is because they are magnetized in the direction of the easy axis of magnetization. That is, the tunnel magnetoresistive element 1 shown in FIG. 1 is formed at a position where the easily magnetized axis of the free magnetic layer 30 is twisted by approximately 90 degrees with respect to the easily magnetized axis of the fixed magnetic layer 10. The arrow 10A shown in column a) indicates the direction of the easy axis of magnetization of the fixed magnetic layer 10, and the arrow 30A indicates the direction of the easy axis of magnetization of the free magnetic layer 30.
As shown in FIGS. 1 (column a), (column b), and (column c), the magnetization direction 10A of the fixed magnetic layer 10 is relatively insensitive to the influence of an external magnetic field and is stable, and the magnetization of the free magnetic layer 30 is increased. The orientation 30A changes under the influence of the external magnetic fields (H1, H2).
As shown in FIG. 1 (column b), when an external magnetic field H1 in the direction opposite to the magnetization direction 10A of the fixed magnetic layer 10 is applied to the tunnel magnetoresistive element 1, the magnetization direction 30A of the free magnetic layer 30 is applied. Spins in the opposite direction of the magnetization direction 10A of the fixed magnetic layer 10, and the resistance of the insulating layer 20 increases due to the tunnel effect (the resistance increases from R0 to R1 in FIG. 1 (column d)). The change in resistance is schematically shown by the thickness of the arrows of the currents I0, I1 and I2 in FIG. 1 (column a) (column b) (column c).
As shown in FIG. 1 (column c), when an external magnetic field H2 in the same direction with respect to the magnetization direction 10A of the fixed magnetic layer 10 is applied to the tunnel magnetoresistive element 1, the magnetization direction 30A of the free magnetic layer 30 is applied. Spins in the same direction as the magnetization direction 10A of the fixed magnetic layer 10, and the resistance of the insulating layer 20 decreases due to the tunnel effect (the resistance decreases from R0 to R2 in FIG. 1 (column d)).
As shown in FIG. 1 (column d), the resistance changes proportionally (the graph is linear) with respect to the strength of the external magnetic field in both the direction of increasing the resistance (vertical axis) and the direction of decreasing the resistance (vertical axis). The tunnel magnetoresistive element 1 having a property (linearity) is ideal.

The conventional tunnel magnetoresistive element 101 shown in FIG. 2 is of the type described in Patent Documents 1-3, in which a fixed magnetic layer 10 is formed at the lower part of the insulating layer 20 and a free magnetic layer 30 is formed at the upper part, and free magnetism is formed. The layer 30 has a laminated structure in which the magnetic coupling layer (Ru) 32 is interposed between the ferromagnetic layer (CoFeB) 31 and the soft magnetic layer (NiFe or CoFeSi) 33.
Specifically, in the conventional tunnel magnetic resistance element 101 _{, the base layer (Ta) 3 is formed on the substrate (Si, SiO 2} ) 2, and the fixed magnetic layer 10 is formed on the base layer (Ta) 3 as a fixed magnetic layer 10 from below. IrMn) 11, the ferromagnetic layer (CoFe) 12, the magnetic coupling layer (Ru) 13, and the ferromagnetic layer (CoFeB) 14 are laminated, and the free magnetic layer 30 is formed on the insulating layer (MgO) 20 via the insulating layer (MgO) 20. It has a laminated structure in which a ferromagnetic layer (CoFeB) 31, a magnetic coupling layer (Ru) 32, and a soft magnetic layer (NiFe or CoFeSi) 33 are laminated from the bottom.
In such a conventional tunnel magnetoresistive element 101, the direction of the easy axis of magnetization of all magnetic layers even if the heat treatment is performed in a magnetic field a plurality of times while applying an external magnetic field in different directions each time. The magnetic resistance characteristics become high hysteresis as shown in FIG. 3, and the above-mentioned linearity cannot be realized. The arrow A1 shown in FIG. 2 is the direction of the easy axis of magnetization of the magnetic layer.

On the other hand, the conventional tunnel magnetoresistive element 102 shown in FIG. 4 is of the type described in Patent Document 3, and has a laminated structure in which the fixed magnetic layer 10 and the free magnetic layer 30 are turned upside down with respect to FIG. ..
In such a conventional tunnel magnetoresistive element 102, the direction of the easy magnetization axis of the free magnetic layer 30 (arrow A1) is formed in a direction different from the direction of the easy magnetization axis of the fixed magnetic layer 10 (arrow A2). It is possible to increase the shape of the free magnetic layer 30 (expected to improve Hk and reduce noise), but it adversely affects the insulating layer 20 and the fixed magnetic layer 10 of the upper layer (caused by deterioration of uniformity and crystallinity). It is expected), and it has become difficult to improve the performance as a magnetic sensor.

Therefore, as shown in FIG. 5, the tunnel magnetic resistance element 1A of the comparative example is fixed from the side close to the substrate 2 that supports the magnetic layers 10 and 30 and the insulating layer 20, similarly to the tunnel magnetic resistance element 101 of the conventional example. The magnetic layer 10, the insulating layer 20, and the free magnetic layer 30 are laminated in this order, and the magnetic coupling layer (Ru) 32 is eliminated from the laminated structure of the conventional tunnel magnetic resistance element 101, and the free magnetic layer 30 has a lower surface. The laminated structure has a ferromagnetic layer 31 bonded to the insulating layer 20 and a soft magnetic layer 33 laminated in contact with the upper surface of the ferromagnetic layer 31.
According to such a laminated structure, the easily magnetized axes of the ferromagnetic layer 31 and the soft magnetic layer 33 constituting the free magnetic layer 30 are in the same direction as each other, and are in different directions with respect to the easily magnetized axes of the fixed magnetic layer 10. It can be formed into a magnetization characteristic at a twisted position (for example, a direction twisted by about 90 degrees), and the above-mentioned linearity can be realized.

(Production method)
A manufacturing method for manufacturing the tunnel magnetoresistive element 1A of the comparative example will be described.
First, as shown in FIG. 6A, after laminating the layers from the substrate 2 to at least the ferromagnetic layer 31, heat treatment is performed on the laminated body while applying an external magnetic field in a predetermined direction (arrow A1) to perform free magnetism. The first magnetic field heat treatment step of forming the easily magnetized axis of the ferromagnetic layer 31 constituting the layer 30 and the easily magnetized axis of the fixed magnetic layer 10 in the same direction is carried out.
After the first magnetic field heat treatment step, as shown in FIG. 6B, the direction is twisted differently from that of the first magnetic field heat treatment step, and an external magnetic field (in the direction of arrow A2) is applied freely. By forming the soft magnetic layer 33 constituting the magnetic layer 30, the easy-to-magnetize axis of the free magnetic layer 30 is oriented in a different direction (for example, a direction twisted by approximately 90 degrees) with respect to the easy-to-magnetize axis of the fixed magnetic layer 10. The film forming step in the magnetic field to be formed is carried out to obtain the laminated structure shown in FIG. 6C.
As shown in FIG. 6C, the easy axes of magnetization of the ferromagnetic layer 31 and the soft magnetic layer 33 constituting the free magnetic layer 30 are the same as each other through the first heat treatment step in a magnetic field and the film forming step in a magnetic field. It can be formed with magnetization characteristics that are in the direction and are in different directions (preferably in a direction twisted by approximately 90 degrees) with respect to the easy axis of magnetization of the fixed magnetic layer 10. That is, the easy-to-magnetize axis of the fixed magnetic layer 10 is formed in the direction of the magnetic field (arrow A1) applied during the first heat treatment step in the magnetic field, and the easy-to-magnetize axis of the free magnetic layer 30 is the film-forming step in the magnetic field. It is formed in the direction of the magnetic field applied at this time (arrow A2).
At this point, the reluctance characteristic with linearity as shown in FIG. 7 is obtained.

Further, it is preferable to carry out the following step after the film forming step in the magnetic field. That is, a second magnetic field heat treatment step is carried out in which the heat treatment is performed while applying an external magnetic field in the same direction (arrow A2) as in the magnetic field film forming step. Further, after the second magnetic field heat treatment step, a third magnetic field heat treatment step is carried out in which the heat treatment is performed while applying an external magnetic field in the same direction (arrow A1) as in the first magnetic field heat treatment step. As a result, as shown in FIGS. 8A and 8B, Hk and Hc can be reduced to increase the sensitivity.

(Effect of set / reset magnetic field on various reluctance sensors)
(In the case of AMR)
As shown in FIGS. 9A and 9B, an AMR element sends a signal that responds to an external magnetic field 55 in a predetermined direction while applying a set magnetic field 53 and a reset magnetic field 54 to a bridge circuit in which two AMR elements 51 and 52 are connected between constant gaps. It is output by the potential of the connection point 56 of 51 and 52.
As shown in FIG. 9A, the magnetization direction 57 of the soft magnetic layer of the AMR element 51 and the magnetization direction 58 of the soft magnetic layer of the AMR element 52 are displaced opposite to each other with respect to the direction in which the current 59 flows. To combine. Due to the influence of the external magnetic field 55 in the direction perpendicular to the direction in which the current 59 flows on the existing planes of the magnetization directions 57 and 58, the magnetization directions 57 and 58 spin as shown by the broken lines, respectively. In the AMR element, the resistance value R is determined by the following equation (1) by the relative angle θ between the direction in which the current 59 flows and the magnetization directions 57 and 58 of the soft magnetic layer. That is, R = R0 + ΔR · sin ² θ ... Equation (1). Here, R0 is the resistance value of the ferromagnetic thin film metal in a non-magnetic field, and ΔR is the amount of change in the resistance value.
Therefore, in FIG. 9A, the resistance value of the AMR element 51 decreases and the resistance value of the AMR element 52 increases, so that the potential of the connection point 56 is positively displaced (+ ΔV).
The magnetization directions 57 and 58 of the soft magnetic layer are reversed between the application of the set magnetic field 53 of FIG. 9A and the application of the reset magnetic field 54 of FIG. 9B.
Therefore, in FIG. 9B, the resistance value of the AMR element 51 increases and the resistance value of the AMR element 52 decreases, so that the potential of the connection point 56 is negatively displaced (−ΔV).
As described above, the polarity of the signal component that responds to the external magnetic field 55 is reversed with respect to the external magnetic field 55 in the same direction when the set magnetic field 53 is applied and when the reset magnetic field 54 is applied. A noise component appears on the output from the connection point 56, but the noise component is not inverted.

The technique described in Non-Patent Document 1 is used as a set / reset circuit in which a set pulse magnetic field and a reset pulse magnetic field that invert the magnetization directions of the soft magnetic layers are alternately applied to the AMR element of the bridge circuit.
The noise component is canceled by giving the output from the connection point 56 to the detection circuit and inverting and adding one of the output when the set magnetic field 53 is applied and the output when the reset magnetic field 54 is applied. Therefore, noise is removed.

(In the case of conventional TMR)
In the tunnel magnetic resistance element 102 of the conventional example and the tunnel magnetic resistance element 1A of the comparative example, the antiferromagnetic layer (Irmn) 11 is commonly present in the fixed magnetic layer 10 and the magnetization direction is strongly fixed. Therefore, as shown in FIGS. 10A and 10B, the magnetization directions 63 and 64 of the fixed magnetic layer do not change depending on the switching between the set magnetic field 53 and the reset magnetic field 54.
That is, as shown in FIGS. 10A and 10B, when a bridge circuit is configured by TMR elements 61 and 62 instead of the AMR elements 51 and 52 of FIGS. 9A and 9B and a set magnetic field 53 and a reset magnetic field 54 are applied. Although the magnetization directions 67 and 68 of the free magnetic layer are reversed, the magnetization directions 63 and 64 of the fixed magnetic layer do not change.
In the TMR element, the change in the resistance value is irrelevant to the direction in which the current flows, and the resistance value R is determined by the following equation (2) by the relative angle θ between the magnetization direction of the free magnetic layer and the magnetization direction of the fixed magnetic layer. .. That is, R = R0 + ΔR · sinθ ... Equation (2). Here, R0 is the resistance value of MTJ in a non-magnetic field, and ΔR is the amount of change in resistance value.
Therefore, in FIG. 10A, the resistance value of the TMR element 61 increases and the resistance value of the TMR element 62 decreases, so that the potential of the connection point 56 is negatively displaced (−ΔV).
In FIG. 10B, the resistance value of the TMR element 61 increases and the resistance value of the TMR element 62 decreases, so that the potential of the connection point 56 is also displaced negatively (−ΔV).
As described above, when the set magnetic field 53 is applied and when the reset magnetic field 54 is applied, the polarity of the signal component responding to the external magnetic field 55 does not reverse with respect to the external magnetic field 55 in the same direction. Noise cannot be removed as in the case.

(In the case of TMR of the present invention)
Therefore, as shown in FIG. 11, the tunnel magnetic resistance element 1B according to the embodiment of the present invention has the antiferromagnetic layer (Irmn) 11 and the ferromagnetic layer (CoFe) 12 with respect to the tunnel magnetic resistance element 1A described above. , The magnetic coupling layer (Ru) 13 was eliminated, and the fixed magnetic layer 10 was only the ferromagnetic layer (CoFeB) 14. The method for manufacturing the tunnel magnetoresistive element 1B of the present invention is the same as the tunnel magnetoresistive element 1A of the comparative example except that the fixed magnetic layer 10 is only the ferromagnetic layer (CoFeB) 14.
By eliminating the antiferromagnetic layer (IrMn) 11, the magnetization directions 73 and 74 of the fixed magnetic layer are reversed depending on the switching between the set magnetic field 53 and the reset magnetic field 54 as shown in FIGS. 12A and 12B. Not only the free magnetic layer 30 but also the fixed magnetic layer 10 is reversed in the direction of magnetization with a magnetic field strength of 1 μT or more and less than 10 mT so that it is reversed by applying a set magnetic field 53 and a reset magnetic field 54 of about 10 mT by the coil. , Its composition and volume (layer thickness and area) are set. The composition of the fixed magnetic layer 10 is a ferromagnetic layer (CoFeB) excluding the antiferromagnetic layer, and a soft magnetic layer in whole or in part, so that the direction of magnetization changes under the influence of an external magnetic field. It may be easy to (reverse).
As shown in FIGS. 12A and 12B, a bridge circuit is configured by TMR elements 71 and 72 (both are TMR elements 1B in FIG. 11) instead of the AMR elements 51 and 52 in FIGS. 9A and 9B, and the set magnetic field 53 and reset are performed. When the magnetic field 54 is applied, the magnetization directions 77 and 78 of the free magnetic layer and the magnetization directions 73 and 74 of the fixed magnetic layer are reversed.
The resistance value R is determined by the above equation (2).
Therefore, in FIG. 12A, the resistance value of the TMR element 71 increases and the resistance value of the TMR element 72 decreases, so that the potential of the connection point 56 is negatively displaced (−ΔV).
In FIG. 12B, the resistance value of the TMR element 71 decreases and the resistance value of the TMR element 72 increases, so that the potential of the connection point 56 is positively displaced (+ ΔV).
As described above, the polarity of the signal component that responds to the external magnetic field 55 is reversed with respect to the external magnetic field 55 in the same direction when the set magnetic field 53 is applied and when the reset magnetic field 54 is applied, as in the AMR. A noise component appears on the output from the connection point 56, but the noise component is not inverted.

The set / reset circuit is applied as in the case of the AMR element, and the output from the connection point 56 is given to the detection circuit. The magnetization direction correction circuit of the present embodiment includes a bridge circuit including the TMR elements 71 and 72 as described above, a set / reset circuit, and a detection circuit.
By inverting and adding one of the output when the set magnetic field 53 is applied and the output when the reset magnetic field 54 is applied, the noise component is canceled out, so that noise is removed.
FIG. 13 shows an outline of signal processing by the detection circuit.
FIG. 13 (column a) shows the signal component SS1 when the set magnetic field 53 is applied and the signal component SR1 when the reset magnetic field 54 is applied. The signal component SS1 and the signal component SR1 are inverted from each other. Further, FIG. 13 (column a) shows a noise component NS1 when the set magnetic field 53 is applied and a noise component NR1 when the reset magnetic field 54 is applied. The noise component NS1 and the noise component NR1 have the same waveform without mutual inversion.
The signal component SS1 on which the noise component NS1 is mounted and the signal component SR1 on which the noise component NR1 is mounted are alternately input to the detection circuit.
Synchronized with the alternating application of the set pulse magnetic field and the reset pulse magnetic field, the detection circuit amplifies the input signal when the set pulse magnetic field is applied (no inversion) as shown in FIG. 13 (column b), and applies the reset pulse magnetic field. Time is inverted and amplified to obtain signal components SS2 and SR2 that are not inverted to each other, and noise components NS2 and NR2 that are inverted to each other. do.

The magnetization direction correction circuit will be described with reference to FIG.
FIG. 14 is a block diagram illustrating an outline of the magnetization direction correction circuit.
A trigger signal (TG) 82 is formed from the standard signal generator (SSG) 81, and the trigger signal is sent to the Power AMP 83 and the Multiplier 84.
A current flows through the coil 85 for generating a set / reset magnetic field by the output from the Power AMP 83, and a pulse magnetic field is applied to the TMR elements 71a, 72a, 71b, 72b.
By repeating the above-mentioned pulse magnetic field generation at high speed (several hundred Hz or more), the signal component SS1 and the signal component SR1 having a signal polarity inversion relationship are output from the bridge circuit to the Pre AMP 86 at high speed.
The Multiplier 84 switches whether to read the signal output from the Pre AMP 86 via the INV AMP (inverting circuit) 87 based on the trigger signal (TG) 82, and aligns the mutually inverted signal polarities in the same direction. .. At this time, the noise component NS1 and the noise component NR1 are in an inverted relationship.
In the sample hold circuit (S / H) 88, only the necessary component of the signal output from the Multiplier 84 is extracted and sent to the low-pass filter circuit (LPF) 89. At this time, in the band where the sampling number is small due to the action of LPF89, the noise component NS1 and the noise component NR1 that are repeatedly output at high speed are canceled out, so that the noise (1 / f noise) in the low frequency region is canceled out. The signal is output to the Main AMP 90 in the state.

According to the TMR element 1B of FIG. 11, since the ferromagnetic layer (CoFe) 12 and the magnetic coupling layer (Ru) 13 are eliminated, the following effects are also obtained.
Magnetic tunnel junction (MTJ) develops a high TMR ratio by annealing in a magnetic field. In order to manufacture a high-performance MTJ, annealing treatment at a higher temperature is required, but functional materials other than MTJ required for applications such as magnetic memory and magnetic sensors, such as magnetic coupling layers and antiferromagnetic materials, are required. It is known that layers and the like lose their characteristics at high temperatures (generally about 400 ° C. above), and because of restrictions on temperature conditions, it is not possible to develop a high TMR ratio.
Therefore, according to the TMR element 1B of FIG. 11, since the ferromagnetic layer (CoFe) 12 and the magnetic coupling layer (Ru) 13 are eliminated, there are less restrictions on the temperature increase of the annealing treatment, and a high TMR ratio is exhibited. Will be easy.

(Example)
15A and 15B show an example of a combination of a free magnetic layer and a fixed magnetic layer that are inverted by the above set pulse magnetic field and reset pulse magnetic field and linearly change the relative angle in the magnetization direction with respect to the external magnetic field.
FIG. 15A shows the magnetization characteristics of the TMR element 1B shown in FIG. 11 in a free magnetic layer in which CoFeB is selected as the ferromagnetic layer 31 and has a predetermined thickness of less than 3 nm, and CoFeSiB is selected as the soft magnetic layer 33 and has a thickness of 100 nm. Is shown.
FIG. 15B shows the magnetization characteristics of the fixed magnetic layer in which CoFeB is selected as the ferromagnetic layer 14 and has a thickness of 3 nm in the TMR element 1B shown in FIG.
As shown in FIG. 15B, in the fixed magnetic layer, the direction of magnetization is reversed by applying a set magnetic field and a reset magnetic field with a swing width of about ± 5 [Oe]. At that time, as shown in FIG. 15A, the direction of magnetization is reversed even in the free magnetic layer, but the direction of magnetization changes linearly due to the influence of the external magnetic field from the position of the reverse shift with a swing width of about ± 5 [Oe]. Therefore, the TMR element (1B), which is a combination of the free magnetic layer and the fixed magnetic layer having such characteristics, linearly changes the relative angle with the magnetization direction of the fixed magnetic layer, as shown in FIG. Has excellent magnetic resistance characteristics. Further, by incorporating it into the magnetization direction correction circuit, it can function as a noiseless, high-precision, high-sensitivity magnetic sensor.

The present invention can be used for magnetic measurement and the like.

1 Tunnel magnetoresistive element 1A, 1B Tunnel magnetoresistive element 2 Substrate 3 Underlayer 10 Fixed magnetic layer 20 Insulation layer 30 Free magnetic layer 14, 31 Ferromagnetic layer 33 Soft magnetic layer

Claims (4)

An insulating layer is arranged between ferromagnetic layers magnetized in at least two specific directions whose magnetization direction changes under the influence of an external magnetic field to form a magnetic tunnel junction, and both sides of the insulating layer are formed. A tunnel magnetoresistive element that changes the resistance of the insulating layer by the tunnel effect according to the relative angle of the magnetization direction of the ferromagnetic layer.
Each of the ferromagnetic layers on both sides of the insulating layer has a composition and volume in which the direction of magnetization is reversed at a magnetic field strength of 1 μT or more and less than 10 mT.
The insulating layer and the ferromagnetic layers on both sides thereof are laminated in the order of the ferromagnetic layer on one side, the insulating layer, and the ferromagnetic layer on the other side from the side closer to the substrate, and the ferromagnetic layer on the other side is the said. Since the soft magnetic layer is laminated in contact with the ferromagnetic layer on the other side, it functions as a free magnetic layer whose direction of magnetization is more likely to change than the ferromagnetic layer on the other side under the influence of an external magnetic field. Tunnel magnetic resistance element. The tunnel magnetoresistive element according to claim 1, wherein the magnetization direction of the ferromagnetic layer on one side and the magnetization direction of the free magnetic layer are in a twisted position. A bridge circuit in which at least one or more tunnel magnetoresistive elements according to claim 1 or 2 are mounted.
A set / reset circuit that alternately applies a set pulse magnetic field and a reset pulse magnetic field that invert the magnetization directions of the ferromagnetic layer to the tunnel magnetoresistive element of the bridge circuit.
A magnetization direction correction circuit including a detection circuit that detects a signal output from the tunnel magnetoresistive element in synchronization with alternating application of a set pulse magnetic field and a reset pulse magnetic field. The magnetization direction correction circuit according to claim 3 , wherein the magnetization direction of the ferromagnetic layer on one side is reversed and the magnetization direction of the free magnetic layer is reversed by alternately applying a set pulse magnetic field and a reset pulse magnetic field.

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