阅读说明：本技术 一种测量磁隧道结自旋相关塞贝克系数的方法 (Method for measuring magnetic tunnel junction spin correlation seebeck coefficient ) 是由 吴琼 其他发明人请求不公开姓名 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隧道结自旋相关塞贝克系数的方法,包括以下步骤：在磁隧道结样品表面镀一层Al薄膜激发层,以飞秒激光作为测试光源,激光脉冲打在Al激发层,测量磁隧道结在高电阻态时(AP)的电压(V-(AP))与低电阻态时(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,计算得到磁隧道结自由层与参考层的温度差(ΔT-(MTJ))；根据公式ΔS-(MTJ)=(V-(AP)-V-P)/ΔT-(MTJ),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 tunnel junction spin correlation seebeck coefficient, which comprises the following steps: plating an Al film excitation layer on the surface of a magnetic tunnel junction sample, taking femtosecond laser as a test light source, striking the Al excitation layer with laser pulses, and measuring the voltage (V) of the magnetic tunnel junction in a high-resistance state (AP) AP ) And voltage (V) at low resistance state (P) P ) (ii) a Simulating the heat conduction process of laser in a sample by using a finite element method through simulation software, and calculating to obtain the temperature difference (delta T) between the free layer and the reference layer of the magnetic tunnel junction MTJ ) (ii) a According to the formula Δ S MTJ =(V AP ‑V P )/ΔT MTJ And the spin-related Seebeck coefficient is obtained by calculation, the measuring method is simpler and faster, the generation of other secondary effects is avoided, and the measurement is more accurate.)

1. A method for measuring the magnetic tunnel junction spin-dependent Seebeck coefficient is characterized in that the measuring process comprises three steps:

(1): firstly plating an Al film on the surface of a magnetic tunnel junction 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 magnetic tunnel junction in a high-resistance state (AP)_AP) And voltage (V) at low resistance 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 free magnetic tunnel junctionTemperature difference (delta) of layer and reference layerT _MTJ）；

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

2. The measurement 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 magnetic tunnel junction is composed of a free layer, a reference layer, an insulating layer, a protective layer and a connecting layer, wherein the protective layer is characterized in that one or more layers of Ru, Ta, Cu and the like are used as the protective layer, the connecting layer is characterized in that one or more layers of Cu, Ta, CuN and the like are used as the connecting layer, and the TMR of the magnetic tunnel junction is 70% -150%; the voltage of the magnetic tunnel junction under the laser pulse in different resistance states 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 free layer and the reference layer of the magnetic tunnel junction is calculatedT _MTJ）。

Technical Field

The invention relates to a method for measuring a magnetic tunnel junction spin-dependent 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. At present, in order to measure the spin-dependent seebeck coefficient in the magnetic tunnel junction, an insulating layer is generally plated on the surface of the magnetic tunnel junction, a heating resistance layer is plated on the insulating layer, a temperature difference is generated at two ends of the magnetic tunnel junction through a resistance heating layer, voltages of the magnetic tunnel junction in different resistance states are measured at the same time, 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 magnetic tunnel junction, so that the complexity of the magnetic tunnel junction 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 magnetic tunnel junction is obtained by combining a virtual simulation means.

Disclosure of Invention

The invention aims to provide a method for measuring a magnetic tunnel junction spin-dependent seebeck coefficient,

the invention provides a method for measuring a self-rotation plug Beck coefficient of a magnetic tunnel junction, which comprises the following steps:

(1): firstly plating an Al film on the surface of a magnetic tunnel junction 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 magnetic tunnel junction in a high-resistance state (AP)_AP) And voltage (V) at low resistance state (P)_P)；

(2): simulating the heat conduction process of laser in a sample by using a finite element method through simulation software, and calculating to obtain the temperature difference (delta) between the free layer and the reference layer of the magnetic tunnel junctionT _MTJ）；

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

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 magnetic tunnel junction in the step (1) is composed of a free layer, a reference layer, an insulating layer, a protective layer and a connecting layer, one or more layers of Ru, Ta, Cu and the like are used as the protective layer, one or more layers of Cu, Ta, CuN and the like are used as the connecting layer, and the TMR of the magnetic tunnel junction is 70% -150%;

specifically, in the measuring method in the step (1), Keithley 2400 is used as a measuring instrument to measure the voltages of the magnetic tunnel junctions in different resistance states under the laser pulse.

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 free layer and the reference layer of the magnetic tunnel junction is calculated and obtainedT _MTJ）。

Compared with the prior art that the spin-dependent Seebeck coefficient in the magnetic tunnel junction is measured by adopting a resistance heating method, the spin-dependent Seebeck coefficient of the magnetic tunnel junction is measured by adopting a laser heating method, the measuring method is simpler and faster, other secondary effects are avoided, and the measurement is more accurate.

Drawings

FIG. 1 is a schematic measurement of a sample.

Detailed Description

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

Example 1: a method of measuring a magnetic tunnel junction spin dependent seebeck coefficient, comprising the steps of:

taking the measurement of spin-related Seebeck coefficient of 200 nm x 300 nm magnetic tunnel junction as an example, the TMR of the magnetic tunnel junction is 120%, the free layer and the reference layer of the magnetic tunnel junction are CoFeB, the insulating layer is MgO, the protective layer is Cu, the connecting layer is CuN, the upper surface of the magnetic tunnel junction is coated with a 100nm Al excitation layer film, femtosecond pulse laser is adopted as a heat source, the laser intensity is 50mW, the light spot size is 5 μm, the laser light spot is directly above the magnetic tunnel junction, the measurement schematic diagram is shown in FIG. 1, the voltage value at two ends of the magnetic tunnel junction in the laser excitation state is measured by using Keithley 2400, and the voltage (V) of the magnetic tunnel junction (AP) in the high resistance state is measured by changing the size of a magnetic field_AP=20.1 μ V) and voltage in low resistance state (V)_P=13.2μV)。

The temperature difference between the free layer and the reference layer of the magnetic tunnel junction is calculated by simulating the heat conduction process of laser in a sample by using a finite element method（ΔT _MTJ= 40 mK), and the magnetic tunnel junction spin correlation seebeck coefficient delta is calculated by a formulaS _MTJ=(V_AP-V_P)/ΔT _MTJ=（20.1-13.2）/0.04=172.5 μV/K。

Example 2: a method of measuring a magnetic tunnel junction spin dependent seebeck coefficient, comprising the steps of:

taking the measurement of spin-related Seebeck coefficient of 100nm x 200 nm magnetic tunnel junction as an example, the TMR is 85%, the free layer and the reference layer of the magnetic tunnel junction are CoFeB, the insulating layer is MgO, the protective layer is Cu, the connecting layer is CuN, the upper surface of the magnetic tunnel junction is coated with a 90nm Al excitation layer film, femtosecond pulse laser is adopted as a heat source, the laser intensity is 100mW, the light spot size is 10 μm, the laser light spot is directly above the magnetic tunnel junction, the voltage value at two ends of the magnetic tunnel junction under the laser excitation state is measured by using Keithley 2400, and the voltage (V) of the magnetic tunnel junction in the high resistance state (AP) is measured by changing the magnetic field size_AP=18.3 μ V) and voltage in low resistance state (V)_P=8.5μV)。

The temperature difference (delta) between the free layer and the reference layer of the magnetic tunnel junction is calculated by simulating the heat conduction process of laser in a sample by using a finite element methodT _MTJ= 73 mK), and the magnetic tunnel junction spin correlation seebeck coefficient delta is calculated by a formulaS _MTJ=(V_AP-V_P)/ΔT _MTJ=（18.3-8.5）/0.073 =134.2 μV/K。