Spin valve type giant magnetoresistance linear sensor based on interlayer DMI field

Abstract

The invention belongs to the technical field of magnetic sensing, and particularly relates to a spin valve type giant magnetoresistance linear sensor based on an interlayer DMI field. According to the novel spin valve type giant magnetoresistance sensing unit structure provided by the invention, an interlayer DMI field is introduced into the spin valve type giant magnetoresistance sensing unit during preparation, so that the ferromagnetic layer 1 enables the magnetic moment of the ferromagnetic layer 2 to be along the short axis direction under the action of the interlayer DMI field; the magnetic moment of the ferromagnetic layer 3 is not influenced by the action of the DMI field between the layers, and the magnetic moment is still oriented along the long axis of the unit; therefore, the magnetic moments of the free layer and the fixed layer of the spin valve type giant magnetoresistance linear sensing unit are in mutual vertical orientation in a null field after plating is completed, and the requirement of linear sensing is met. According to the invention, the DMI field in the field of spintronics is combined with the giant magnetoresistance effect, and the preparation can be completed at one time without any additional process and external magnetic field bias setting, so that the manufacturing cost and difficulty are reduced, and the preparation simplification and the stability of the sensing unit are greatly ensured.

Description

Technical Field

[0001] The invention belongs to the field of magnetic sensing technology, relates to magnetic materials and components, and specifically is a spin valve type giant magnetoresistance linear sensor based on an interlayer DMI field. Background Art

[0002] With the advent of the era of the Internet of Everything, the development of sensing technology has attracted much attention from researchers. Magnetic sensors based on the giant magnetoresistance effect are widely used in the sensing field due to their high integration and sensitivity, excellent stability and linearity.

[0003] The giant magnetoresistance effect is based on a spin effect in magnetic multilayer films, which is common in multilayer films with ferromagnetic metals and non-magnetic metals arranged adjacent to each other at a specific thickness. In this structure, when the magnetic moments in the multilayer ferromagnetic metal layers are arranged in parallel, the multilayer film presents a low resistance state, and when the magnetic moments in the multilayer ferromagnetic metal layers are arranged in opposite directions, the multilayer film presents a high resistance state. The magnetic moment arrangement between the multilayer film layers can be modulated by applying an external magnetic field to achieve changes in the output signal.

[0004] The spin valve structure is the most commonly used structure in giant magnetoresistance sensors. Its basic structure is ferromagnetic layer 1 (free layer) / non-magnetic metal (isolation layer) / ferromagnetic layer 2 (fixed layer) / antiferromagnetic layer. In practical applications, the magnetic moment of the free layer changes with the size and direction of the external magnetic field. Due to the effect of the pinning field, the magnetic moment of the fixed layer remains unchanged in its original direction when the external magnetic field is smaller than the pinning field. Under magnetic fields of different sizes within a certain range, the relative magnetic moment orientations of the two ferromagnetic films are different, the resistances are different, and the output electrical signal sizes are different. The size of the magnetic field can be detected by the size of the output signal.

[0005] In order to realize the linear sensing function of the spin valve giant magnetoresistive sensor, during the preparation process, it is usually required that the magnetic moment of the free layer and the magnetic moment of the fixed layer are perpendicular to each other under zero field. In the current giant magnetoresistive linear sensors, in order to make the magnetic moments of the two realize vertical orientation, a permanent magnetic bias magnetic field is often added to modulate the direction of the magnetic moment of the free layer, or a mutually perpendicular magnetic field is applied during the deposition process of the free layer and the fixed layer film, or annealing is performed after the film is plated, etc., to achieve the requirement that the magnetic moment of the free layer and the magnetic moment of the fixed layer are perpendicular to each other under zero field. When the permanent magnetic bias method is adopted, an additional structure will be introduced, which will not only increase the volume of the device, but also increase the difficulty of the overall preparation of the device; and by applying mutually perpendicular magnetic fields during the preparation process or lateral annealing after the film is plated, the requirements for the coating equipment and the complexity of the process implementation will be increased, making the linear region control of the sensing unit complicated. Summary of the invention

[0006] In view of the above-mentioned problems or deficiencies, in order to solve the process cost problem of realizing the perpendicularity of the magnetic moments of the free layer and the fixed layer under zero field in the existing spin valve type giant magnetoresistive sensor, the present invention provides a spin valve type giant magnetoresistive linear sensor based on the interlayer DMI field. In the preparation process, the perpendicular orientation of the magnetic moments of the free layer and the fixed layer of the spin valve type giant magnetoresistive linear sensor under zero field is realized, and the DMI field in the field of spin electronics is combined with the giant magnetoresistive effect. The spin valve type giant magnetoresistive linear sensor can be prepared by one-time plating without additional processes, which reduces the production cost and difficulty of the spin valve type giant magnetoresistive linear sensor. The prepared linear sensor can be widely used in the detection of other physical quantities such as magnetic field, current, angular velocity, acceleration, etc.

[0007] A spin valve type giant magnetoresistive linear sensor based on interlayer DMI field: a substrate / heavy metal layer 1 / ferromagnetic layer 1 / heavy metal layer 2 / ferromagnetic layer 2 (free layer) / non-magnetic metal layer (isolation layer) / ferromagnetic layer 3 (fixed layer) / antiferromagnetic layer / covering layer stacked in sequence from bottom to top, such as Figure 1 shown.

[0008] The ferromagnetic layer 2 (free layer) / non-magnetic metal layer (isolation layer) / ferromagnetic layer 3 (fixed layer) / antiferromagnetic layer constitute a conventional spin valve type giant magnetoresistance unit.

[0009] The heavy metal layer 1 is used to assist the ferromagnetic layer 1 in achieving out-of-plane growth of the magnetic moment. In the ferromagnetic layer 1 / heavy metal layer 2 / ferromagnetic layer 2 (free layer) part, the magnetic moment in the ferromagnetic layer 1 is out-of-plane, and the magnetic moment in the ferromagnetic layer 2 (free layer) is in-plane. The interlayer DMI field is generated between the ferromagnetic layer 1 and the ferromagnetic layer 2 through the process during preparation. The DMI field is combined with the giant magnetoresistance effect, so that the ferromagnetic layer 1, through the action of the interlayer DMI field, makes the magnetic moment of the ferromagnetic layer 2 along the short axis direction in the initial state after preparation, while the magnetic moment of the ferromagnetic layer 3 is not affected by the action of the interlayer DMI field, and its magnetic moment is still oriented along the long axis of the unit in the initial state after preparation. In this way, after the spin valve type giant magnetoresistance unit is prepared, its free layer and fixed layer magnetic moments are oriented perpendicular to each other under zero field.

[0010] The interlayer DMI field magnitude of ferromagnetic layer 1 to ferromagnetic layer 2 is given by Decide, is the magnetization vector of the ferromagnetic layer 1, is the DMI field vector, whose direction is determined by the symmetry theorem.

[0011] Furthermore, the interlayer DMI field is generated between the ferromagnetic layer 1 and the ferromagnetic layer 2 by adjusting the thickness of the heavy metal layer 2 and controlling it by a special deposition method, and according to the three-dimensional Lévy-Fert model, an interlayer DMI field is generated between the ferromagnetic layer 1 and the ferromagnetic layer 2 in the structure.

[0012] Furthermore, the special deposition method is an inclined angle sputtering method. Specifically, the inclined angle sputtering method is selected. The direction of H acting on the ferromagnetic layer 2 is perpendicular to the beam direction of the deposited heavy metal layer 2. IL-DMI The field is along the short axis. When the heavy metal layer 2 is sputtered at an inclined angle, the beam direction for depositing the heavy metal layer 2 should be set along the short axis of the spin-valve giant magnetoresistance unit.

[0013] Furthermore, the spin valve type giant magnetoresistance unit uses a commonly used zigzag type (such as Figure 2 shown).

[0014] Furthermore, the substrate material is SiO2 / Si or a glass substrate. The material of the heavy metal layers 1 and 2 is a heavy metal (Pt, W, Ta, etc.) having a spin Hall angle.

[0015] Further, the ferromagnetic layers 1, 2, 3 are made of Ni, Co, Fe or Ni, Co, Fe alloy ferromagnetic metal materials, wherein the thickness of the ferromagnetic layer 1 is selected to be 0.5-1.5 nm in order to make the magnetic moment of the ferromagnetic layer 1 oriented out of the plane; the thickness of the ferromagnetic layers 2 and 3 is selected to correspond to the typical thickness for generating the spin valve type giant magnetoresistance effect, such as 2-10 nm, and their magnetic moments are oriented in the plane;

[0016] Furthermore, the isolation layer is made of non-magnetic metal material (Cu, Cr, Au or Ag) with a thickness of 2.5-3.5 nm; the antiferromagnetic layer is made of IrMn, FeMn, PtMn, etc. with a thickness of 8-15 nm.

[0017] Furthermore, the top-layer covering material is Ta to prevent the structure from being oxidized and contaminated, thereby increasing the stability of the device.

[0018] The method for preparing the spin valve type giant magnetoresistance linear sensor based on the interlayer DMI field comprises the following steps:

[0019] Step 1: On a substrate, photolithography is performed to form a folded line shape of a desired spin valve type giant magnetoresistive linear sensor unit;

[0020] Step 2: Place the photolithographic substrate in a magnetron sputtering device and deposit the following thin film deposition processes in sequence:

[0021] Heavy metal layer 1 / ferromagnetic layer 1 / heavy metal layer 2 / ferromagnetic layer 2 / non-magnetic metal layer / ferromagnetic layer 3 / antiferromagnetic layer / covering layer, wherein except for the heavy metal layer 2 which is sputtered at an inclined angle, the other layers are all deposited by conventional uniform thin film coating methods; wherein when sputtering at an inclined angle, the beam direction of the deposited heavy metal layer 2 is set along the short axis of the zigzag spin valve type giant magnetoresistance unit;

[0022] Step 3: After the film structure is plated, the photoresist on the substrate surface is removed, leaving the long fold line sensing unit;

[0023] Step 4: Based on the above, a second standard photolithography process is performed on the substrate again to photolithograph the electrode pattern;

[0024] Step 5: After the secondary photolithography is completed, the electrode is plated using a thin film magnetron sputtering process; finally, the photoresist on the substrate surface is removed again to obtain a spin valve type giant magnetoresistive linear sensor based on the interlayer DMI field.

[0025] The present invention proposes a novel spin valve type giant magnetoresistance sensing unit structure. Starting from the thin film structure itself, the magnetic moments of the free layer and the pinned layer are perpendicular to each other when the thin film is plated. The present invention introduces the interlayer DMI field into the spin valve type giant magnetoresistance sensing unit, so that the ferromagnetic layer 1 makes the magnetic moment of the ferromagnetic layer 2 (free layer) along the short axis direction through the action of the interlayer DMI field; while the magnetic moment of the ferromagnetic layer 3 (fixed layer) is not affected by the action of the interlayer DMI field, and its magnetic moment is still oriented along the long axis of the unit; at this time, the spin valve type giant magnetoresistance linear sensing unit can be realized. The magnetic moments of the free layer and the fixed layer are perpendicular to each other under zero field after the plating is completed, meeting the needs of the spin valve type giant magnetoresistance unit for linear sensing.

[0026] In summary, the present invention can be completed at one time during preparation, without any additional process and external magnetic field bias setting, which greatly ensures the simplicity of preparation and the stability of the sensor unit, omits additional processes, reduces production costs, improves production efficiency, and greatly reduces production difficulty. The prepared linear sensor can be widely used in the detection of other physical quantities such as magnetic field, current, angular velocity, acceleration, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the film structure of the present invention;

[0028] Figure 2 The schematic diagram of the shape of the zigzag linear spin valve type giant magnetoresistance sensor unit of the embodiment;

[0029] Figure 3 This is a magnetoresistance test curve of the spin valve giant magnetoresistance linear sensor prepared in the embodiment.

[0030] Reference numerals: 1 - heavy metal layer 1, 2 - ferromagnetic layer 1, 3 - heavy metal layer 2, 4 - ferromagnetic layer 2, 5 - isolation layer, 6 - ferromagnetic layer 3, 7 - antiferromagnetic layer, 8 - cover layer. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0032] A spin valve type giant magnetoresistance linear sensor based on an interlayer DMI field, the preparation method comprising the following steps:

[0033] Step 1: On a SiO2 substrate, a standardized lift-off photolithography process is used to photolithograph the required spin valve type giant magnetoresistance linear sensor unit in a zigzag strip shape. The spin valve type giant magnetoresistance unit of this embodiment uses a commonly used zigzag line shape (such as Figure 2 shown).

[0034] Step 2: Place the photolithographic substrate in a magnetron sputtering device and deposit the following layers in sequence using a thin film deposition process: Pt (0.6nm) / CoFe (1nm) / Pt (3nm) / CoFe (3nm) / Cu (3nm) / CoFe (5nm) / IrMn (12nm) / Ta (5nm). Except for the heavy metal layer 2 (3nmPt) which is sputtered at an inclined angle, all other layers are deposited using a conventional uniform thin film coating method. When sputtering at an inclined angle, the beam direction of the deposited Pt layer is set along the short axis of the zigzag spin valve type giant magnetoresistance unit.

[0035] Step 3: After the coating is completed, use acetone to remove the photoresist on the surface of the substrate, leaving a long fold line sensor unit.

[0036] Step 4: Based on the above, a second standard photolithography process is performed on the substrate again to photolithograph the electrode pattern. The electrode pattern prepared this time is a 200 micron × 180 micron rectangle.

[0037] Step 5: After the secondary photolithography is completed, a Cu (100 nm) electrode is plated using a thin film magnetron sputtering process. Finally, the photoresist on the substrate surface is removed again using acetone to obtain a spin valve type giant magnetoresistive linear sensor based on the interlayer DMI field, such as Figure 2 shown.

[0038] After the preparation is completed, a current of I = 1 mA is connected to the two electrodes A and B, and an external magnetic field is applied along the long axis of the sensor unit from -100Oe to +100Oe, and then from +100Oe to -100Oe. At the same time, the voltage V output at both ends of the electrodes A and B is measured. out . Using R(H)=V out / I, calculate the resistance value of the sensor unit under different magnetic fields. Figure 3 The magnetoresistance ratio MR of the magnetoresistance sensor unit prepared in the embodiment changes with the external magnetic field, MR = (R(H) - R min ) / R min *100%, where R(H) is the resistance value of the sensor unit under a magnetic field of magnitude H, R min is the minimum value of the sensor unit during the test.

[0039] It can be seen from the tested magnetoresistance curve that the magnetoresistance test curve of this embodiment changes linearly with the size of the external magnetic field and has basically no hysteresis. It can be judged that during the plating process, the free layer magnetic moment and the fixed layer magnetic moment of this linear sensing unit are oriented perpendicular to each other at zero field. The present invention provides a new idea for the preparation of spin valve type giant magnetoresistance linear sensors, simplifies the preparation process, and improves the stability and consistency of thin film deposition.

[0040] From the above embodiments, it can be seen that the present invention proposes a new spin valve type giant magnetoresistance sensing unit structure, by introducing the interlayer DMI field into the spin valve type giant magnetoresistance sensing unit during preparation, so that the ferromagnetic layer 1 makes the magnetic moment of the ferromagnetic layer 2 along the short axis direction through the action of the interlayer DMI field; while the magnetic moment of the ferromagnetic layer 3 is not affected by the action of the interlayer DMI field, and its magnetic moment is still oriented along the long axis of the unit; thus, the spin valve type giant magnetoresistance linear sensing unit is realized, and the magnetic moments of the free layer and the fixed layer are mutually perpendicularly oriented under zero field after plating, meeting the needs of linear sensing. The present invention combines the DMI field in the field of spin electronics with the giant magnetoresistance effect, which can be completed at one time during preparation without any additional process and external magnetic field bias setting, reducing the production cost and difficulty, and greatly ensuring the simplicity of preparation and the stability of the sensing unit.

Claims

1. A spin valve type giant magnetoresistance linear sensor based on interlayer DMI field, characterized in that: The substrate / heavy metal layer 1 / ferromagnetic layer 1 / heavy metal layer 2 / ferromagnetic layer 2 / non-magnetic metal layer / ferromagnetic layer 3 / antiferromagnetic layer / covering layer are stacked in sequence from bottom to top; The ferromagnetic layer 2 is used as a free layer, the non-magnetic metal layer is used as an isolation layer, and the ferromagnetic layer 3 is used as a fixed layer; wherein the ferromagnetic layer 2 / non-magnetic metal layer / ferromagnetic layer 3 / antiferromagnetic layer constitute a conventional spin valve type giant magnetoresistance unit; The heavy metal layer 1 is used to assist the ferromagnetic layer 1 in achieving out-of-plane growth of the magnetic moment. In the ferromagnetic layer 1 / heavy metal layer 2 / ferromagnetic layer 2 part, the magnetic moment in the ferromagnetic layer 1 is out-of-plane, and the magnetic moment in the ferromagnetic layer 2 is in-plane. An interlayer DMI field is generated between the ferromagnetic layer 1 and the ferromagnetic layer 2 through the process during preparation. The DMI field is combined with the giant magnetoresistance effect, so that the ferromagnetic layer 1 is caused by the action of the interlayer DMI field to make the magnetic moment of the ferromagnetic layer 2 along the short axis direction in the initial state after preparation, while the magnetic moment of the ferromagnetic layer 3 is not affected by the action of the interlayer DMI field, and its magnetic moment is still oriented along the long axis of the unit in the initial state after preparation, thereby realizing that after the spin valve type giant magnetoresistance unit is prepared, the magnetic moments of the free layer and the fixed layer are oriented perpendicular to each other under zero field. The interlayer DMI field magnitude of ferromagnetic layer 1 to ferromagnetic layer 2 is given by Decide, is the magnetization vector of the ferromagnetic layer 1, is the DMI field vector, whose direction is determined by the symmetry theorem.

2. The spin valve type giant magnetoresistance linear sensor based on interlayer DMI field as claimed in claim 1, characterized in that: The method of generating an interlayer DMI field between the ferromagnetic layer 1 and the ferromagnetic layer 2 is as follows: by adjusting the thickness of the heavy metal layer 2 and controlling it by a special deposition method, an interlayer DMI field is generated between the ferromagnetic layer 1 and the ferromagnetic layer 2 in the structure according to the three-dimensional Lévy-Fert model.

3. The spin valve type giant magnetoresistance linear sensor based on interlayer DMI field as claimed in claim 2, characterized in that: The special deposition method is an inclined angle sputtering method, The direction of the beam is perpendicular to the direction of the deposited heavy metal layer 2; in order to make the H acting on the ferromagnetic layer 2 IL-DMI The field is along the short axis. When the heavy metal layer 2 is sputtered at an inclined angle, the beam direction for depositing the heavy metal layer 2 is set along the short axis of the spin valve type giant magnetoresistance unit.

4. The spin valve type giant magnetoresistance linear sensor based on interlayer DMI field as claimed in claim 1, characterized in that: The spin valve type giant magnetoresistance unit adopts the commonly used zigzag type.

5. The spin valve type giant magnetoresistance linear sensor based on interlayer DMI field as claimed in claim 1, characterized in that: The substrate material is SiO2 / Si or a glass substrate; the material of the heavy metal layers 1 and 2 is a heavy metal having a spin Hall angle.

6. The spin valve type giant magnetoresistance linear sensor based on interlayer DMI field as claimed in claim 1, characterized in that: The ferromagnetic layers 1, 2, 3 are made of Ni, Co, Fe or Ni, Co, Fe alloy ferromagnetic metal materials, wherein the ferromagnetic layer 1 has a thickness of 0.5-1.5nm so that the magnetic moment is oriented out of the plane; the thickness of the ferromagnetic layers 2 and 3 is 2-10nm, and their magnetic moments are oriented in the plane.

7. The spin valve type giant magnetoresistance linear sensor based on interlayer DMI field as claimed in claim 1, characterized in that: The isolation layer is made of Cu, Cr, Au or Ag, and its thickness is 2.5-3.5 nm; the antiferromagnetic layer is made of IrMn, FeMn or PtMn, and its thickness is 8-15 nm.

8. The spin valve type giant magnetoresistance linear sensor based on interlayer DMI field as claimed in claim 1, characterized in that: The top layer covering material is Ta to prevent the structure from being oxidized and contaminated, thereby increasing the stability of the device.

9. The method for preparing a spin valve type giant magnetoresistive linear sensor based on an interlayer DMI field according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: On a substrate, photolithography is performed to form a folded line shape of a desired spin valve type giant magnetoresistive linear sensor unit; Step 2: Place the photolithographic substrate in a magnetron sputtering device and deposit the following thin film deposition processes in sequence: Heavy metal layer 1 / ferromagnetic layer 1 / heavy metal layer 2 / ferromagnetic layer 2 / non-magnetic metal layer / ferromagnetic layer 3 / antiferromagnetic layer / covering layer, wherein except for the heavy metal layer 2 which is sputtered at an inclined angle, the other layers are all formed by conventional uniform thin film coating methods; When sputtering at an inclined angle, the beam direction of the deposited heavy metal layer 2 is set along the short axis of the zigzag spin valve type giant magnetoresistance unit; Step 3: After the film structure is plated, the photoresist on the substrate surface is removed, leaving the long fold line sensing unit; Step 4: Based on the above, a second standard photolithography process is performed on the substrate again to photolithograph the electrode pattern; Step 5: After the secondary photolithography is completed, the electrode is plated using a thin film magnetron sputtering process; Finally, the photoresist on the substrate surface is removed again to obtain a spin valve type giant magnetoresistance linear sensor based on the interlayer DMI field.

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