CN113314667B - A Magnetic Thin Film Material Structure Based on SOT Effect to Generate Bias - Google Patents

Abstract

The invention relates to a magnetic thin film material structure biased based on the SOT effect, the magnetic thin film material structure adopts a top pinning structure or a bottom pinning structure, and the magnetic thin film material structure includes a base, a seed layer, and a spin generation layer , antiferromagnetic pinned layer, ferromagnetic pinned layer, nonmagnetic interlayer, soft magnetic free layer and cover layer, the material of the spin generation layer is heavy metal, nonmagnetic metal, crystal thin film or concha A kind of metal. In the magnetic thin film material structure of the present invention, the material for the spin generation layer is one of heavy metal, non-magnetic metal, crystal thin film or semimetal of the outer ear. Due to the specific material of the spin generation layer, the adjacent antiferromagnetic ferromagnetic The layer is biased, and the direction of the bias will be changed by changing the direction of the current, and the magnitude of the bias can be changed by changing the magnitude of the current density.

Description

A Magnetic Thin Film Material Structure Biased Based on SOT Effect

technical field

The invention relates to a magnetic thin film material structure that generates bias based on the SOT effect, and belongs to the field of magnetic materials.

Background technique

Magnetoresistance refers to the phenomenon that the resistance of materials changes under the action of an external magnetic field. Magnetoresistance devices have been widely used in sensors, storage and other fields. The giant magnetoresistance GMR and tunnel magnetoresistance TMR structures are mainly composed of two magnetic metal layers and a spacer layer sandwiched between them. Common structures include multilayer film systems, pseudo spin valve systems, spin valve systems, and artificially synthesized antiferroic materials. Magnetic spin valve system, etc. Since the multilayer film system needs to align the magnetic moments of adjacent ferromagnetic layers antiparallel through antiferromagnetic interlayer coupling at zero magnetic field, although it can produce high MR values, it also requires a high saturation field. There is coupling between the hard magnetic layer and the free layer in the pseudo-spin valve system, which leads to an increase in the coercive force of the free layer and reduces the sensitivity. The spin valve system and the artificially synthesized antiferromagnetic spin valve system can use the antiferromagnetic layer to pin a soft magnetic layer through exchange under the condition that there is no exchange coupling between the two soft magnetic layers, so that the magnetization is fixed at In a certain direction, only the unpinned soft magnetic layer can be flipped freely under a small magnetic field, and a large MR value can be generated under a small magnetic field, which is beneficial to practical applications.

Spin valves and synthetic antiferromagnetic spin valves are mainly composed of four layers: ferromagnetic free layer, nonmagnetic layer, ferromagnetic pinning layer, and antiferromagnetic layer. When the exchange coupling effect of the antiferromagnetic layer causes the magnetization of the adjacent ferromagnetic layer to be pinned in a certain direction, the pinning has been maintained in this direction under a small field and is not easy to change. Only when the external field is large enough, the pinning The magnetic moment of the pinned layer will be reversed, and the magnetic moment of the free layer will be reversed accordingly, showing no MR effect. Therefore, the SOT (spin-orbit torque) effect can produce pinning in different directions by changing the direction of the current in a small field range.

At present, the spin valve structure and the artificial antiferromagnetic spin valve structure are dominant. These two structures can pin the antiferromagnetic layer in a specific direction through high temperature and magnetic field annealing, resulting in the pinning of the adjacent ferromagnetic layer in a specific direction. bias. However, this bias direction is fixed, and it is impossible to generate bias in other directions. In practical applications (such as using a Wheatstone full-bridge structure to induce a magnetic field), each bridge arm needs to be pinned in opposite directions. Obviously, the spin valve structure pinned in a specific direction and the artificially synthesized antiferromagnetic spin valve The structure limits its scope of application. Make each bridge arm pin in the opposite direction, with complex and difficult-to-control magnetization technology and additional complex process In the prior art, it is difficult to prepare two opposite pinning directions on one chip, and multi-chip splicing is usually used However, it is difficult to avoid mechanical errors when splicing multiple chips, resulting in low sensitivity and low yield of finished products, which is difficult to meet the needs of mass production. Therefore, it is necessary to develop an improved magnetic film stack structure that can form biases in different directions.

CN109300495A discloses a magnetic structure based on an artificial antiferromagnetic free layer and a spin-orbit moment-magnetic random storage device, which includes a magnetic tunnel junction based on an artificial antiferromagnetic free layer controlled by an electric field and a spin-orbit Moment material layer; the free layer based on the artificial antiferromagnetic device can be controlled by an electric field to realize the transition from the antiferromagnetic state to the ferromagnetic state. The device can realize stable writing of data under the joint action of electric field and current, and has the advantages of simple structure, low power consumption, high speed, radiation resistance and non-volatility. However, this magnetic structure requires a specific structure to realize the function of the memory, and an auxiliary current needs to be applied to help determine the direction of the bias when generating the SOT, which poses a major challenge to the tolerance and processing of the device.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a magnetic thin film material structure that generates bias based on the SOT effect. The magnetic thin film material structure of the present invention can bias the adjacent antiferromagnetic ferromagnetic layer, change the direction of the bias by changing the direction of the current, and change the magnitude of the bias by changing the magnitude of the current density.

Spin-orbit torque (SOT) effect: When the current passes through a system with strong spin-orbit coupling, the generated spin current or spin accumulation at the interface will generate a torque on the adjacent magnetic layer, and the torque will be It can affect the magnetodynamic process of the magnetic layer, and even cause the magnetic moment of the magnetic material to flip under certain conditions.

To achieve the above object, the present invention is achieved through the following technical solutions:

A magnetic thin film material structure biased based on the SOT effect, the magnetic thin film material structure adopts a top pinning structure or a bottom pinning structure, and the magnetic thin film material structure includes a substrate, a seed layer, a spin generation layer, an antiferro Magnetic pinning layer, ferromagnetic pinned layer, non-magnetic interlayer, soft magnetic free layer and cover layer, the production material of described spin generation layer is heavy metal, non-magnetic metal, crystal thin film or outer ear semimetal A sort of.

Preferably according to the present invention, the heavy metal is one of Ta, W, Pt, Au, Hf or Mo.

Preferably according to the invention, the non-magnetic metal is Ti.

Preferably according to the present invention, the crystal thin film is Bi ₂ Se ₃ thin film, Bi ₂ Te ₃ thin film, Sb ₂ Te ₃ thin film, Bi _x Se _1-x thin film or (Bi _x Sb _1-x ) ₂ Te ₃ thin film, x< 1.

Crystal thin films are prior art materials.

Preferably according to the present invention, the Weyl semimetal is single crystal, polycrystalline or amorphous Weyl semimetal, and the Weyl semimetal is selected from WTe2, MoTe ₂ or Mo _x W _1-x Te ₂ , where x<1.

Preferably according to the present invention, the seed layer is made of one or a combination of two or more of Ta, Ru, W, Mo, Ir, Pt, NiFe, NiFeCr, and NiCr.

Preferably according to the present invention, the antiferromagnetic pinning layer is made of one or more combinations of IrMn, PtMn, FeMn, NiMn, PdMn ferromagnetic metals, or NiO, CoO, α-Fe2O3 oxide antiferromagnetic one of the materials.

Preferably according to the present invention, the soft magnetic free layer and the ferromagnetic pinned layer are made of CoFeB, CoFe, Co, Fe, Ni, CoCrPt, NiFe, CoFeSiB, (Co/Pt)m, (Co/Ni)n , (Co/Pd)p or semi-metallic materials, where m, n, p refer to the number of repetitions of the multilayer stack.

Further preferably, the semi-metallic material is an XXZ type Heusler alloy or an X ₂ YZ type Heusler alloy, wherein X is selected from one or more combinations of Mn, Co, Fe, Ni, Pd, Cu, and Y is selected from Ti, V, one or more combinations of Cr, Mn, Fe, Co or Ni, and Z selected from one or more combinations of Al, Ga, In, Si, Ge, Sn or Sb.

Preferably according to the present invention, the material for making the non-magnetic interlayer is oxide, nitride, oxynitride, metal or alloy.

Further preferably, the constituent elements of oxides, nitrides and oxynitrides are selected from one or more of Mg, Al, Ti, Hf, Cu, Si, In, La, Ca, Sr, V, Zn or Eu combination.

Further preferably, the constituent elements of the metal or alloy are one or a combination of two or more of Cu, Ru, Ag, Au, Ti, Mo, W, Cr, Rh, Ta, Al, Nb, Os, Mg, V .

Preferably according to the present invention, the ferromagnetic pinned layer is a synthetic antiferromagnetic structure (SAF) or a spin valve structure, the spin valve structure comprises a ferromagnetic pinned layer, and the synthetic antiferromagnetic structure (SAF) comprises a ferromagnetic The pinned layer 1 , the ferromagnetic pinned layer 2 and the spacer layer between the ferromagnetic pinned layer 1 and the ferromagnetic pinned layer 2 .

Further preferably, the material for the spacer layer is one or a combination of two or more of Ru, Ta, W, Mo, Nb, Cr, Re, Os, Ir, Au, Ag or Cu.

A magnetic thin film material structure biased based on the SOT effect, the magnetic thin film material structure adopts a bottom pinning structure, which is a synthetic antiferromagnetic structure (SAF) or a spin valve structure;

When it is a spin valve structure, the magnetic thin film material structure sequentially includes a substrate, a seed layer, a spin generation layer, an antiferromagnetic pinning layer, a ferromagnetic pinned layer, a nonmagnetic interlayer, Soft magnetic free layer and cover layer;

When it is a synthetic antiferromagnetic structure (SAF), the magnetic thin film material structure includes, from bottom to top, a substrate, a seed layer, a spin generation layer, an antiferromagnetic pinning layer, a ferromagnetic pinned layer 1, Spacer layer, ferromagnetic pinned layer 2, non-magnetic interlayer, soft magnetic free layer and cover layer.

A magnetic thin film material structure biased based on the SOT effect, the magnetic thin film material structure adopts a top pinning structure, which is a synthetic antiferromagnetic structure (SAF) or a spin valve structure;

When it is a spin valve structure, the magnetic thin film material structure includes a substrate, a seed layer, a soft magnetic free layer, a nonmagnetic interlayer, a ferromagnetic pinned layer, an antiferromagnetic pinned layer, a self- spin generation layer, and covering layer;

When it is a synthetic antiferromagnetic structure (SAF), the magnetic thin film material structure sequentially includes a substrate, a seed layer, a soft magnetic free layer, a nonmagnetic interlayer, a ferromagnetic pinned layer 2, a spacer layer, Ferromagnetic pinned layer 1, antiferromagnetic pinned layer, spin generation layer, and capping layer.

Wherein, the magnetization directions of the soft magnetic free layer and the ferromagnetic pinned layer can be in-plane or out-of-plane.

The present invention generates a biased magnetic film material structure based on the SOT effect, and each layer can be formed by a suitable film-forming method, including physical vapor deposition (PVD), molecular beam epitaxy (MBE), laser pulse deposition (PLD), and atomic layer deposition. (ALD), chemical vapor deposition (CVD), electroplating or a combination thereof.

For the spin generation layer, the current flow direction is 90 degrees to the pinning direction of the antiferromagnetic pinning layer, and after the current is reversed, the pinning direction of the antiferromagnetic pinning layer also changes by 180 degrees. As shown in Figure 5, the spin generation layer Pt and the antiferromagnetic pinning layer IrMn, passing current through Pt will generate torque on IrMn (τ∝m×(m×p), m is the direction of the magnetic moment of IrMn, p is the spin direction), so that the IrMn surface magnetic moments are arranged along this direction to form the pinning direction of this direction. For the current density of 106-107 A/cm2, and the current needs to flow in laterally, the currents mentioned above are all direct currents.

Technical characteristics and advantages of the present invention:

1, the magnetic thin film material structure of the present invention, the making material of spin generation layer is a kind of in heavy metal, non-magnetic metal, crystal thin film or concha semimetal, because the specific material of spin generation layer can make adjacent antiferromagnetic The ferromagnetic layer is biased, and the direction of the bias will be changed by changing the direction of the current, and the magnitude of the bias can be changed by changing the magnitude of the current density.

2. The structure of the magnetic thin film material of the present invention can form a pinned reverse full-bridge structure on a single membrane stack, which has flexibility in the design of the sensor. According to different applications, the sensitivity and measurement range can be adjusted, and it has strong compatibility with CMOS , can be directly prepared on the ASIC circuit, and has a simple structure and a small chip area.

Description of drawings

Fig. 1 is the schematic structural diagram of the spin valve magnetic film material structure of the bottom pinning structure of embodiment 1;

Fig. 2 is the structural representation of the artificially synthesized antiferromagnetic thin film material of the bottom pinning structure of embodiment 2;

3 is a schematic structural view of a spin valve magnetic thin film material with a top pinning structure in Example 3;

Fig. 4 is the structural representation of the artificially synthesized antiferromagnetic thin film material of the top pinning structure of embodiment 4;

Figure 5 The current flow direction of the spin generation layer and the pinning direction of the antiferromagnetic pinning layer;

Fig. 6 is when not adding electric current among the embodiment 1, the original magnetization curve figure of film material structure;

Fig. 7 is the magnetization curve of the thin film material structure at an applied current density of 2.5x10 ⁷ A/cm ² in Example 1, generating a positive bias field H _ex ;

Fig. 8 is the magnetization curve of the thin film material structure in Example 1 when the applied current density is -2.5x10 ⁷ A/cm ² , and a negative bias field He _ex is generated.

Detailed ways

The present invention will be further limited below in conjunction with the accompanying drawings and embodiments, but not limited thereto.

Example 1

The structure of the magnetic thin film material biased based on the SOT effect, specifically the spin valve magnetic thin film material with the bottom pinning structure, is shown in Figure 1, including Si/SiO ₂ substrate, 2nm Ta seed layer, 8nm Pt spin generation layer, 8nm IrMn antiferromagnetic pinning layer, 5nm CoFe ferromagnetic pinned layer, 1.8nm Cu nonmagnetic interlayer, CoFe 1nm/NiFe2nm soft magnetic free layer and 2nm Ta capping layer.

Made into strips with a length of 80 μm and a width of 10 μm by micromachining. When no current is applied to both ends of the strip, the original magnetization curve is measured, as shown in Figure 6, and there is no bias effect. When a current with a current density of 2.5x10 ⁷ A/cm ² is applied to both ends of the strip, the measured magnetization curve is shown in Figure 7, and a bias magnetic field (+H _ex ) in the positive direction is generated. When the current density is applied in the opposite direction When the current is 2.5x10 ⁷ A/cm ² (-2.5x10 ⁷ A/cm ² ), the measured magnetization curve is shown in Fig. 8, and a bias magnetic field (-H _ex ) in the negative direction is generated. Hereby explain, the description of the current direction here: we call the current direction of positive bias as positive, and the current direction of negative bias as negative.

Example 2

The magnetic thin film material structure biased based on the SOT effect, specifically the artificially synthesized antiferromagnetic magnetic thin film material with a bottom pinning structure, the structure is shown in Figure 2, including Si/SiO ₂ substrate, 2nm Ta seed from bottom to top layer, 8nm Pt spin generation layer, 8nm IrMn antiferromagnetic pinning layer, 5nm CoFe ferromagnetic pinned layer 1, 2nm Ta spacer layer, 5nm CoFeB ferromagnetic pinned layer 2, 1.8nm Cu nonmagnetic interlayer , CoFe 1nm/NiFe 2nm soft magnetic free layer and 2nm Ta capping layer.

Example 3

The magnetic thin film material structure biased based on the SOT effect, specifically the spin valve magnetic thin film material with a top pinning structure; the structure is shown in Figure 3, including Si/SiO ₂ substrate, 2nm Ta seed layer, CoFe 1nm/NiFe2nm soft magnetic free layer, 1.8nm Cu nonmagnetic interlayer, 5nm CoFe ferromagnetic pinned layer, 8nm IrMn antiferromagnetic pinned layer, 8nm Pt spin generation layer, and 2nm Ta capping layer.

Example 4

The structure of the magnetic thin film material biased based on the SOT effect, specifically the artificially synthesized antiferromagnetic magnetic thin film material with the top pinning structure, the structure is shown in Figure 4, including Si/SiO ₂ substrate, 2nm Ta seed layer, CoFe1nm/NiFe2nm soft magnetic free layer, 1.8nm Cu nonmagnetic interlayer, 5nm CoFeB ferromagnetic pinned layer 2, 2nm Ta spacer layer, 5nm CoFe ferromagnetic pinned layer 1, 8nm IrMn antiferromagnetic pinned layer layer, 8nm Pt spin generation layer, and 2nm Ta capping layer.

Example 5

It is the same as the magnetic thin film material structure based on the SOT effect described in Embodiment 1, except that the spin generation layer is made of Ta.

Example 6

It is the same as the magnetic thin film material structure based on the SOT effect described in Embodiment 1, except that the spin generation layer is made of Hf.

Example 7

It is the same as the magnetic thin film material structure based on the SOT effect described in Embodiment 1, except that the spin generation layer is made of Ti.

Example 8

It is the same as the magnetic thin film material structure based on the SOT effect described in Embodiment 1, except that the spin generation layer is made of Bi ₂ Se ₃ thin film.

Example 9

It is the same as the magnetic thin film material structure based on the SOT effect described in Embodiment 1, except that the spin generation layer is made of WTe2.

Example 10

It is the same as the magnetic thin film material structure based on the SOT effect described in Embodiment 1, except that the spin generation layer is made of MoTe ₂ .

Claims (4)

1. Magnetic film material structure for generating bias based on SOT effect, in particular to spin valve magnetic film material with bottom pinning structure, which sequentially comprises Si/SiO from bottom to top ₂ A substrate, a 2nm Ta seed layer, an 8nm Pt spin-generating layer, an 8nm IrMn antiferromagnetic pinning layer, a 5nm CoFe ferromagnetic pinned layer, a 1.8nm Cu nonmagnetic interlayer, a CoFe 1nm/NiFe2nm soft magnetic free layer, and a 2nm Ta capping layer.

2. Magnetic thin film material structure for generating bias based on SOT effect, in particular to artificial synthetic antiferromagnetic magnetic thin film material with bottom pinning structure, which sequentially comprises Si/SiO from bottom to top ₂ A substrate, a 2nm Ta seed layer, an 8nm Pt spin-generating layer, an 8nm IrMn antiferromagnetic pinning layer, a 5nm CoFe ferromagnetic pinned layer, a 2nm Ta spacer layer, a 5nm CoFeB ferromagnetic pinned layer, a 1.8nm Cu nonmagnetic interlayer, a CoFe 1nm/NiFe2nm soft magnetic free layer, and a 2nm Ta capping layer.

3. Magnetic thin film material for generating bias based on SOT effectThe material structure is specifically a spin valve magnetic film material with a top pinning structure; sequentially comprises Si/SiO from bottom to top ₂ A substrate, a 2nm Ta seed layer, a CoFe 1nm/NiFe2nm soft magnetic free layer, a 1.8nm Cu nonmagnetic interlayer, a 5nm CoFe ferromagnetic pinned layer, an 8nm IrMn antiferromagnetic pinning layer, an 8nm Pt spin generating layer, and a 2nm Ta capping layer.

4. Magnetic thin film material structure for generating bias based on SOT effect, in particular to artificial synthetic antiferromagnetic magnetic thin film material with top pinning structure, which sequentially comprises Si/SiO from bottom to top ₂ A substrate, a 2nm Ta seed layer, a CoFe 1nm/NiFe2nm soft magnetic free layer, a 1.8nm Cu nonmagnetic interlayer, a 5nm CoFeB ferromagnetic pinned layer, a 2nm Ta spacer layer, a 5nm CoFe ferromagnetic pinned layer, an 8nm IrMn antiferromagnetic pinning layer, an 8nm Pt spin generating layer, and a 2nm Ta capping layer.

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