A spin valve type giant magnetoresistance linear sensor based on the interlayer DMI field

Abstract

The present invention belongs to the field of magnetic sensing technology, and specifically relates to a spin-valve type giant magnetoresistive linear sensor based on the interlayer DMI field. The present invention proposes a new structure of a spin-valve type giant magnetoresistive sensing unit. By introducing the interlayer DMI field into the spin-valve type giant magnetoresistive sensing unit during preparation, the magnetic moment of ferromagnetic layer 2 is along the short axis direction by the action of the interlayer DMI field on ferromagnetic layer 1; while the magnetic moment of ferromagnetic layer 3 is not affected by the action of this interlayer DMI field, and its magnetic moment still aligns along the long axis of the unit; thereby realizing that the magnetic moments of the free layer and the fixed layer of the spin-valve type giant magnetoresistive linear sensing unit are perpendicular to each other under zero field after plating, meeting the requirements of linear sensing. The present invention combines the DMI field in the field of spintronics with the giant magnetoresistive effect, which can be completed in one step during preparation, without any additional processes and external magnetic field bias settings, reducing the manufacturing cost and difficulty, and greatly ensuring the simplicity of preparation and the stability of the sensing unit.

Description

Technical Field

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

[0002] With the advent of the era of 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, etc.

[0003] The giant magnetoresistance effect is a spin effect based on magnetic multilayers, which is commonly found in multilayers with a structure in which ferromagnetic metals and non-magnetic metals are arranged adjacent to each other according to specific thicknesses. 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 the opposite direction, the multilayer film presents a high-resistance state. The magnetic moment arrangement between the multi-film layers can be modulated by an external magnetic field to achieve a change in the output signal.

[0004] The spin-valve structure is the most commonly used structure in giant magnetoresistive 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 magnitude and direction of the external magnetic field. Due to the action of the pinning field, the magnetic moment of the fixed layer remains in its original direction when the external magnetic field is less than the pinning field. Under different magnetic fields of a certain range, the relative magnetic moment orientations of the two ferromagnetic films are different, the resistances are different, and the magnitudes of the output electrical signals are different. The magnitude of the magnetic field can be detected by the magnitude of the output signal.

[0005] To achieve the linear sensing function of the spin-valve type giant magnetoresistive sensor, during the preparation process, it is usually required that the magnetic moment of its free layer and the magnetic moment of the fixed layer are perpendicular to each other in zero field. In current giant magnetoresistive linear sensors, in order to make the magnetic moments of the two perpendicular to each other, an external permanent magnetic bias field is often applied to modulate the direction of the magnetic moment of the free layer, or mutually perpendicular magnetic fields are applied during the deposition process of the free layer and the fixed layer film layers, or annealing is performed after the film layers are deposited, etc., to meet the requirement that the magnetic moment of the free layer and the magnetic moment of the fixed layer are perpendicular to each other in zero field. When the permanent magnetic bias method is used, an additional structure will be introduced, which will not only increase the volume of the device but also increase the overall preparation difficulty of the device; while by applying mutually perpendicular magnetic fields during the preparation process or the transverse annealing process after the film layers are deposited, the requirements for the coating equipment and the complexity of the process implementation will be increased, making the regulation of the linear region 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 making the magnetic moments of the free layer and the fixed layer of the existing spin valve type giant magnetoresistive sensor perpendicular to each other in zero field, the present invention provides a spin valve type giant magnetoresistive linear sensor based on the interlayer DMI field. During the preparation process, the magnetic moments of the free layer and the fixed layer of the spin valve type giant magnetoresistive linear sensor are made perpendicular to each other in zero field. By combining the DMI field in the field of spintronics with the giant magnetoresistive effect, a spin valve type giant magnetoresistive linear sensor can be prepared by one-time plating without additional processes, reducing the manufacturing 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, and acceleration.

[0007] A spin valve type giant magnetoresistive linear sensor based on the interlayer DMI field: It is 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 / cover layer stacked in sequence from bottom to top, 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 to achieve out-of-plane growth of the magnetic moment. In the part of the ferromagnetic layer 1 / heavy metal layer 2 / ferromagnetic layer 2 (free layer), 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. And through the process during preparation, an interlayer DMI field is generated between the ferromagnetic layer 1 and the ferromagnetic layer 2; by combining the DMI field with the giant magnetoresistive effect, the magnetic moment of the ferromagnetic layer 2 is made along the short axis direction in the initial state after preparation under the action of the interlayer DMI field by the ferromagnetic layer 1, while the magnetic moment of the ferromagnetic layer 3 is not affected by the action of this interlayer DMI field, and its magnetic moment is still along the long axis orientation of the unit in the initial state after preparation. Furthermore, after the spin valve type giant magnetoresistance unit is prepared, the magnetic moments of its free layer and fixed layer are perpendicular to each other in zero field;

[0010] The magnitude of the interlayer DMI field of the ferromagnetic layer 1 on the ferromagnetic layer 2 is determined by determined, is the magnetization vector of the ferromagnetic layer 1, is the DMI field vector, and its direction is determined by the symmetry theorem.

[0011] Furthermore, the method for generating the interlayer DMI field between the ferromagnetic layer 1 and the ferromagnetic layer 2: It is controlled by adjusting the thickness of the heavy metal layer 2 and a special deposition method. 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 this structure.

[0012] Further, the special deposition method is the inclined angle sputtering method. Specifically: inclined angle sputtering is selected, and its direction is perpendicular to the beam direction of depositing the heavy metal layer 2. To make the H IL-DMI field acting on the ferromagnetic layer 2 along the short axis, when the heavy metal layer 2 is sputtered at an inclined angle, the beam direction of depositing the heavy metal layer 2 should be set along the short axis of the spin valve type giant magnetoresistance unit.

[0013] Further, the spin valve type giant magnetoresistance unit is selected as the common folded line type (as Figure 2 shown).

[0014] Further, the substrate material is SiO2 / Si or a glass substrate. The materials of the heavy metal layers 1 and 2 are heavy metals (such as Pt, W, Ta, etc.) with a spin Hall angle.

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

[0016] Further, the isolation layer is selected from non-magnetic metal materials (such as Cu, Cr, Au or Ag), and its thickness is 2.5 - 3.5 nm; the material of the antiferromagnetic layer is IrMn, FeMn, PtMn, etc., and its thickness is 8 - 15 nm.

[0017] Further, the top covering material is selected as Ta to prevent the structure from being oxidized and polluted, and to increase the stability of the device.

[0018] The preparation method of the above-mentioned spin valve type giant magnetoresistance linear sensor based on the interlayer DMI field includes the following steps:

[0019] Step 1: On the substrate, lithograph the folded line shape of the required spin valve type giant magnetoresistance linear sensor unit;

[0020] Step 2: Place the lithographed substrate in a magnetron sputtering device, and successively deposit by thin film deposition process:

[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, where except for the heavy metal layer 2 which is sputtered at an inclined angle, other layers are all plated by the conventional uniform thin film method; when sputtering at an inclined angle, set the beam direction of the deposited heavy metal layer 2 along the short axis of the folded line spin valve type giant magnetoresistance unit;

[0022] Step 3: After depositing the film layer structure, remove the photoresist on the substrate surface, leaving the long strip zigzag sensing unit;

[0023] Step 4: On this basis, perform a secondary standard photolithography process on the substrate again to lithograph the electrode pattern;

[0024] Step 5: After the secondary lithography is completed, deposit the electrodes using the thin film magnetron sputtering process; finally, remove the photoresist on the substrate surface again, and the spin valve type giant magnetoresistive linear sensor based on the interlayer DMI field is obtained.

[0025] The present invention proposes a novel spin valve type giant magnetoresistive sensing unit structure. Starting from the thin film structure itself, the magnetic moments of its free layer and pinned layer are perpendicular to each other during thin film deposition. By introducing the interlayer DMI field into the spin valve type giant magnetoresistive sensing unit, the magnetic moment of ferromagnetic layer 2 (free layer) is along the short axis direction under the action of the interlayer DMI field by ferromagnetic layer 1; while the magnetic moment of ferromagnetic layer 3 (fixed layer) is not affected by the action of this interlayer DMI field, and its magnetic moment still aligns along the long axis of the unit; at this time, it can be realized that the magnetic moments of the free layer and the fixed layer of the spin valve type giant magnetoresistive linear sensing unit are perpendicular to each other under zero field after deposition, meeting the requirements for the application of the spin valve type giant magnetoresistive unit in linear sensing.

[0026] In summary, the present invention can be completed at one time during preparation, without any additional processes and external magnetic field bias settings, greatly ensuring the simplicity of preparation and the stability of the sensing unit, omitting additional processes, reducing the manufacturing cost, improving the manufacturing efficiency, greatly reducing the manufacturing difficulty, and the prepared linear sensor can be widely used in the detection of other physical quantities such as magnetic field, current, angular velocity, and acceleration. Description of the Drawings

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

[0028] Figure 2 It is a schematic diagram of the shape of the zigzag linear spin valve type giant magnetoresistive sensing unit in the embodiment;

[0029] Figure 3 It is a magnetic resistance test curve graph of the spin valve type giant magnetoresistive 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 - covering layer. Detailed Embodiment

[0031] The following further describes the present invention in detail with reference to the drawings and embodiments.

[0032] A spin valve type giant magnetoresistive linear sensor based on the interlayer DMI field, and the preparation method comprises the following steps:

[0033] Step 1: On a SiO2 substrate, by using a standardized lift-off lithography process, lithograph out the required broken-line long-strip shape of the spin valve type giant magnetoresistive linear sensor unit. In this embodiment, the spin valve type giant magnetoresistive unit selects a commonly used broken-line type (as Figure 2 shown).

[0034] Step 2: Place the lithographed substrate in a magnetron sputtering device, and sequentially deposit by using a thin film deposition process: Pt (0.6 nm) / CoFe (1 nm) / Pt (3 nm) / CoFe (3 nm) / Cu (3 nm) / CoFe (5 nm) / IrMn (12 nm) / Ta (5 nm). Except that the heavy metal layer 2 (3 nm Pt) is sputtered at an inclined angle, other layers are all plated by using a conventional uniform thin film plating method. When sputtering at an inclined angle, set the beam current direction of the deposited Pt layer along the short axis of the broken-line spin valve type giant magnetoresistive unit.

[0035] Step 3: After the film coating is completed, use acetone to remove the photoresist on the surface of the substrate, leaving the long-strip broken-line sensing unit.

[0036] Step 4: On the basis of the above, perform a secondary standard lithography process on the substrate again, and lithograph out the electrode pattern. The electrode pattern prepared this time is a rectangle of 200 microns × 180 microns.

[0037] Step 5: After the secondary lithography is completed, use a thin film magnetron sputtering process to plate a Cu (100 nm) electrode. Finally, use acetone again to remove the photoresist on the surface of the substrate, and the spin valve type giant magnetoresistive linear sensor based on the interlayer DMI field is obtained, as Figure 2 shown.

[0038] After the preparation is completed, connect a current of I = 1 mA to the two electrodes A and B, apply an external magnetic field that changes from -100 Oe to +100 Oe and then from +100 Oe to -100 Oe along the long axis direction of the sensing unit, and simultaneously measure the voltage V out . By using R(H)=V out / I, calculate the resistance values of the sensing unit under different magnetic field magnitudes. Figure 3 is the curve of the magnetic resistance ratio MR varying with the applied magnetic field for the magnetoresistive sensing unit prepared in the embodiment. MR=(R(H)-R min ) / R min *100%, where R(H) is the resistance value of the sensing unit when the magnetic field magnitude is H, and R min is the minimum value of the sensing unit during the test.

[0039] It can be seen from the measured magnetoresistance curve that the magnetoresistance test curve of this embodiment changes linearly with the magnitude of the applied magnetic field and has basically no magnetic 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 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] As can be seen from the above embodiments, the present invention proposes a new structure of a spin valve type giant magnetoresistance sensing unit. By introducing the interlayer DMI field into the spin valve type giant magnetoresistance sensing unit during preparation, the magnetic moment of ferromagnetic layer 2 is along the short axis direction by the action of the interlayer DMI field on ferromagnetic layer 1; while the magnetic moment of ferromagnetic layer 3 is not affected by the action of this interlayer DMI field, and its magnetic moment still aligns along the long axis of the unit; furthermore, it is realized that the free layer and fixed layer magnetic moments of the spin valve type giant magnetoresistance linear sensing unit are perpendicular to each other at zero field after plating, meeting the requirements of linear sensing. The present invention combines the DMI field in the field of spintronics with the giant magnetoresistance effect, which can be completed at one time during preparation without any additional processes and external magnetic field bias settings, reducing the manufacturing cost and difficulty, and greatly ensuring the simplicity of preparation and the stability of the sensing unit.

Claims

1. A spin valve type giant magnetoresistive linear sensor based on the interlayer DMI field, characterized in that: A substrate, a heavy metal layer 1, a ferromagnetic layer 1, a heavy metal layer 2, a ferromagnetic layer 2, a non-magnetic metal layer, a ferromagnetic layer 3, an antiferromagnetic layer, and a capping layer, which are stacked layer by layer from bottom to top; The ferromagnetic layer 2 serves as the free layer, the non-magnetic metal layer serves as the spacer layer, and the ferromagnetic layer 3 serves as the pinned layer; among them, the ferromagnetic layer 2 / non-magnetic metal layer / ferromagnetic layer 3 / antiferromagnetic layer constitutes a spin-valve type giant magnetoresistance unit; The heavy metal layer 1 is used to assist the ferromagnetic layer 1 to achieve out-of-plane growth of the magnetic moment. Among the ferromagnetic layer 1, the heavy metal layer 2, and the ferromagnetic layer 2, the magnetic moment in the ferromagnetic layer 1 is out of the plane, the magnetic moment in the ferromagnetic layer 2 is in the plane, and an interlayer DMI field is generated between the ferromagnetic layer 1 and the ferromagnetic layer 2 through the process during preparation; so that the magnetic moment of the ferromagnetic layer 2 is along the short axis direction in the initial state after preparation under the action of the interlayer DMI field by the ferromagnetic layer 1, while the magnetic moment of the ferromagnetic layer 3 is not affected by the action of this interlayer DMI field, and its magnetic moment is still along the long axis orientation of the unit in the initial state after preparation, thereby realizing that the magnetic moments of the free layer and the pinned layer of the spin-valve type giant magnetoresistance unit are perpendicular to each other under zero field after preparation; The magnitude of the interlayer DMI field of ferromagnetic layer 1 on ferromagnetic layer 2 is determined by determined by is the magnetization vector of ferromagnetic layer 1, is the DMI field vector, and its direction is determined by the symmetry theorem; The method for generating the interlayer DMI field between the ferromagnetic layer 1 and the ferromagnetic layer 2: It is controlled by adjusting the thickness of the heavy metal layer 2 and the inclined angle sputtering method. According to the three-dimensional Lévy-Fert model, an interlayer DMI field is generated between the ferromagnetic layer 1 and the ferromagnetic layer 2; The inclined angle sputtering method is perpendicular to the beam direction for depositing the heavy metal layer 2; to make the H IL-DMI field act along the short axis, when sputtering the heavy metal layer 2 at an inclined angle, set the beam direction for depositing the heavy metal layer 2 along the short axis of the spin valve type giant magnetoresistance element.

2. The spin valve type giant magnetoresistance linear sensor based on the interlayer DMI field according to claim 1, wherein: The spin-valve type giant magnetoresistance unit is selected to be zigzag-shaped.

3. The spin valve type giant magnetoresistance linear sensor based on the interlayer DMI field according to claim 1, characterized in that: The substrate material is SiO2, Si, or a glass substrate; the materials of the heavy metal layers 1 and 2 are heavy metals with a spin Hall angle.

4. The spin valve type giant magnetoresistance linear sensor based on the interlayer DMI field according to claim 1, characterized in that: The ferromagnetic layers 1, 2, and 3 are selected from Ni, Co, Fe, or Ni, Co, Fe alloy ferromagnetic metal materials. Among them, to make the magnetic moment of the ferromagnetic layer 1 oriented out of the plane, the thickness is 0.5 - 1.5 nm; the thicknesses of the ferromagnetic layers 2 and 3 are selected to be 2 - 10 nm, and their magnetic moments are oriented in the plane.

5. The spin valve type giant magnetoresistance linear sensor based on the interlayer DMI field according to claim 1, characterized in that: The spacer layer is selected from Cu, Cr, Au, or Ag, and its thickness is 2.5 - 3.5 nm; the antiferromagnetic layer is selected from IrMn, FeMn, or PtMn, and its thickness is 8 - 15 nm.

6. The spin valve type giant magnetoresistance linear sensor based on the interlayer DMI field as described in claim 1, characterized in that: The capping layer material is selected from Ta to prevent the structure from being oxidized and contaminated and increase the stability of the device.

7. The preparation method of the spin valve type giant magnetoresistance linear sensor based on the interlayer DMI field according to any one of claims 1-6, characterized in that, It includes the following steps: Step 1: On the substrate, lithographically pattern the zigzag shape of the required spin-valve type giant magnetoresistance linear sensor unit; Step 2: Place the lithographed substrate in a magnetron sputtering device and sequentially deposit by thin film deposition process: The heavy metal layer 1, the ferromagnetic layer 1, the heavy metal layer 2, the ferromagnetic layer 2, the non-magnetic metal layer, the ferromagnetic layer 3, the antiferromagnetic layer, and the capping layer. Among them, except for the heavy metal layer 2 which is deposited by inclined angle sputtering, the other layers are all deposited by uniform thin film plating method; When depositing by inclined angle sputtering, set the beam direction of the deposited heavy metal layer 2 along the short axis of the zigzag spin-valve type giant magnetoresistance unit; Step 3: After depositing the film layer structure, remove the photoresist on the substrate surface, leaving a long strip zigzag sensing unit; Step 4: Perform a secondary standard lithography process on the substrate again to lithographically pattern the electrode pattern; Step 5: After the secondary lithography is completed, deposit the electrodes by thin film magnetron sputtering process; Finally, the photoresist on the substrate surface is removed again to obtain the spin valve type giant magnetoresistive linear sensor based on the interlayer DMI field.

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