阅读说明：本技术 一种测量磁性多层膜自旋阀自旋塞贝克系数的方法 (Method for measuring magnetic multilayer film spin valve spin seebeck coefficient ) 是由 杨杭福 黄霞妮 吴琼 泮敏翔 葛洪良 于 2020-12-31 设计创作，主要内容包括：本发明公开了一种测量磁性多层膜自旋阀自旋塞贝克系数的方法,包括以下步骤：在磁性多层膜自旋阀样品表面镀一层Al薄膜作为激发层,以飞秒激光作为测量光源,激光脉冲打在Al激发层,测量自旋阀在反平行态(AP)的电压(V-(AP))与平行态时(P)的电压(V-P)；通过仿真软件,利用有限元法模拟激光在样品中的热传导过程,计算得到自旋阀上下表面的温度差(ΔT-(sv))；根据公式ΔS-(sv)=(V-(AP)-V-P)/ΔT-(sv),计算得到自旋相关的塞贝克系数。本发明的测量手段更加简单快捷,并且避免了其他次生效应的产生,测量更加准确。(The invention discloses a method for measuring a magnetic multilayer film spin valve spin seebeck coefficient, which comprises the following steps: plating an Al film on the surface of a magnetic multilayer film spin valve sample as an excitation layer, using femtosecond laser as a measuring light source, striking the Al excitation layer with laser pulses, and measuring the voltage (V) of the spin valve in an antiparallel state (AP) AP ) With the voltage (V) in the parallel state (P) P ) (ii) a Simulating the heat conduction process of the laser in the sample by using a finite element method through simulation software, and calculating to obtain the temperature difference (delta) of the upper surface and the lower surface of the spin valve T sv ) (ii) a According to the formula Δ S sv =(V AP ‑V P )/Δ T sv And calculating to obtain the spin-dependent seebeck coefficient. The measuring method is simpler and faster, avoids other secondary effects, and is more accurate in measurement.)

1. A method for measuring the spin valve spin Seebeck coefficient of a magnetic multilayer film is characterized in that the measuring process comprises three steps:

(1): firstly plating an Al film on the surface of a magnetic multilayer film spin valve sample as an excitation layer, taking femtosecond laser as a measuring light source, striking laser pulses on the Al excitation layer, and measuring the voltage (V) of the spin valve in an antiparallel state (AP)_AP) With the voltage (V) in the parallel state (P)_P)；

(2): simulating the heat conduction process of the laser in the sample by using a finite element method through simulation software, and calculating to obtain the temperature difference (delta) of the upper surface and the lower surface of the spin valveT _sv）；

(3): spin-dependent seebeck coefficient calculation: according to the formula ΔS _sv=(V_AP-V_P)/ΔT _svAnd calculating to obtain the spin-dependent seebeck coefficient.

2. The measuring method according to claim 1, wherein the thickness of the Al excitation layer thin film in the step (1) is 80nm to 100nm, the laser is a femtosecond pulse laser, the laser intensity is 1mW to 100mW, and the spot size is 5 μm to 20 μm; the spin valve is mainly composed of a magnetic (FM)/non-magnetic (NFM) multilayer film [ FM/NFM ] and a connection layer]_nThe spin valve is characterized in that n is 3-60, the connecting layer is characterized in that one or more layers of Pt, Au, Cu, CuN and the like are used as the connecting layer, and GMR of the spin valve is 1% -50%; the voltage of the spin valve at different resistance states under the laser pulse was measured using Keithley 2400 as a measuring instrument.

3. The method according to claim 1, wherein the simulation software in step (2) is a finite element simulation software such as Comsol, and the temperature difference (Δ) between the spin valve free layer and the reference layer is calculatedT _sv）。

Technical Field

The invention relates to a method for measuring a magnetic multilayer film spin valve spin seebeck coefficient, belonging to the technical field of measurement and sensing.

Background

The combination of spintronics and thermoelectrics in magnetic nanostructures can be used to develop future pure spin-based devices and apply them in sensing and magnetic data storage. Recent findings have shown that pure spin currents can be generated by thermal gradients, promoting this emerging field of spin-thermionic chemistry. However, there is still a need for a deep understanding of the thermoelectric voltage signals in nanoscale magnetic structures.

The spin-dependent seebeck coefficient is an important research content in spin-thermionic science, and how to accurately measure the coefficient is a difficulty of the research. Currently in order to measure the spin-dependent seebeck coefficient of a spin valve of a magnetic multilayer film,

generally, an insulating layer is plated on the surface of the spin valve, a heating resistor layer is plated on the insulating layer, temperature difference is generated at two ends of the spin valve through the resistance heating layer, voltages of the spin valve in different resistance states are measured simultaneously, and the spin-dependent seebeck coefficient of the magnetic tunnel is obtained through calculation. The method has two disadvantages, namely, two films need to be additionally plated at two ends of the spin valve, so that the complexity of the spin valve is increased; and secondly, other secondary effects can be brought in the resistance heating process, such as an additional magnetic field generated by heating current and the like, so that the invention provides a method for heating by adopting laser, two defects in the measurement process are effectively avoided, and the spin-related Seebeck coefficient of the spin valve is obtained by combining a virtual simulation means.

Disclosure of Invention

The invention aims to provide a method for measuring a spin valve spin seebeck coefficient of a magnetic multilayer film,

the invention provides a method for measuring a self-cock Beck coefficient of a magnetic multilayer film spin valve, which comprises the following steps:

(1): firstly plating an Al film on the surface of a magnetic multilayer film spin valve sample as an excitation layer, taking femtosecond laser as a measuring light source, striking laser pulses on the Al excitation layer, and measuring the voltage (V) of the spin valve in an antiparallel state (AP)_AP) With the voltage (V) in the parallel state (P)_P)；

(2): simulating the heat conduction process of the laser in the sample by using a finite element method through simulation software, and calculating to obtain the temperature difference (delta) of the upper surface and the lower surface of the spin valveT _sv）；

(3): spin-dependent seebeck coefficient calculation: according to the formula ΔS _sv=(V_AP-V_P)/ΔT _svMeter for measuringThe spin-dependent seebeck coefficient is calculated.

Specifically, the thickness of the Al excitation layer film in the step (1) is 80 nm-100 nm, the laser is femtosecond pulse laser, the laser intensity is 1 mW-100 mW, and the spot size is 5 μm-20 μm.

Specifically, the spin valve described in the step (1) is mainly composed of a magnetic (FM)/non-magnetic (NFM) multilayer film, and a connection layer, and the multilayer film is [ FM/NFM ]]_nN is 3-60, one or more layers of Pt, Au, Cu, CuN and the like are used as connecting layers, and GMR of the spin valve is 1% -50%.

Specifically, the measuring method in the step (1) uses Keithley 2400 as a measuring instrument to measure the voltage of the spin valve under the laser pulse in different resistance states.

Specifically, the simulation software in the step (2) is finite element simulation software such as Comsol and the like, and the temperature difference (delta) between the spin valve free layer and the reference layer is calculated and obtainedT _SV）。

Compared with the conventional resistance heating method for measuring the spin-related Seebeck coefficient in the spin valve, the laser heating method adopted by the invention for measuring the spin-related Seebeck coefficient of the spin valve is simpler and faster in measuring means, avoids the generation of other secondary effects and is more accurate in measurement.

Drawings

FIG. 1, schematic view of a sample apparatus for measurement.

Detailed Description

The present invention will be further described with reference to the following specific embodiments and comparative examples.

Example 1: a method for measuring the spin valve spin Seebeck coefficient of a magnetic multilayer film comprises the following steps: taking the spin-valve spin-dependent Seebeck coefficient of a magnetic multilayer film for measuring 200 nm × 200 nm as an example, the structure is Pt (3)/[ Co (4)/Cu (2)]₂₀Co (4) Pt (3), wherein the number in brackets is thickness, unit is nanometer, GMR of the sample is about 23%, firstly plating a 100nm Al excitation layer film on the upper surface of the spin valve, adopting femtosecond pulse laser as a heat source, the laser intensity is 50mW, the spot size is 5 μm, excitingThe measurement schematic diagram is shown in fig. 1, Keithley 2400 is used for measuring voltage values at two ends of the spin valve in a laser excitation state, and voltage (V) of the spin valve in an antiparallel state (AP) is measured by changing the size of a magnetic field_AP=4.2 μ V) and voltage in parallel state (V)_P=3.1μV)。

The temperature difference (delta) between the two Pt connection layers in spin was calculated by simulating the heat conduction process of the laser in the sample using the finite element methodT _sv= 520 mK), the spin-dependent seebeck coefficient Δ of the spin valve is calculated by the formulaS _sv=(V_AP-V_P)/ΔT _sv=（4.2-3.1）/0.52=2.11μV/K。

Example 2: a method for measuring the spin valve spin Seebeck coefficient of a magnetic multilayer film comprises the following steps: taking the measurement of spin-valve spin-dependent Seebeck coefficient of 100nm × 300 nm magnetic multilayer film as an example, the structure is Pt (5)/[ Ni [)₈₀Fe₂₀(2)/Cu(2)]₃Ni₈₀Fe₂₀(2) Pt (5), wherein GMR of a sample is about 3%, firstly plating a 100nm Al excitation layer film on the upper surface of the spin valve, adopting femtosecond pulse laser as a heat source, wherein the laser intensity is 100mW, the light spot size is 10 μm, the light spot is shot right above the spin valve, measuring the voltage value at two ends of the spin valve in a laser excitation state by using Keithley 2400, and measuring the voltage (V) of the spin valve in an antiparallel state (AP) by changing the size of a magnetic field_AP=1.3 μ V) and voltage in parallel state (V)_P=1.2μV)。

The temperature difference (delta) between two Pt connecting layers in the spin valve is calculated by simulating the heat conduction process of laser in a sample by using a finite element methodT _sv= 82 mK), the spin-dependent seebeck coefficient Δ of the spin valve is calculated by a formulaS _sv=(V_AP-V_P)/ΔT _sv=（1.3-1.2）/0.082=1.21 μV/K。