CN102709466A - Room-temperature tunneling anisotropic magnetoresistance device and preparation method thereof - Google Patents

Abstract

The invention discloses a room temperature tunnel anisotropic magnetoresistance device and a preparation method thereof. The device structure includes: substrate, bottom electrode, ferromagnetic layer (FM), antiferromagnetic layer, tunneling layer and top electrode; wherein, the ferromagnetic layer is composed of perpendicular magnetization film, including vertical magnetization [Co/ Pt] _n , [Co/Pd] _n , [Co/Ni] _n multilayer film (n=1~10), the thickness of Co in the ferromagnetic layer is 0.3nm~0.8nm, and the thickness of Pt, Pd, Ni is 0.8nm~1.5nm; the antiferromagnetic layer is made of Mn alloy with a thickness of 2nm~6nm; the tunneling layer is MgO or Al ₂ O ₃ with a thickness of 1.5nm~2.5nm. The invention utilizes the exchange coupling effect of the perpendicularly magnetized ferromagnetic layer on one side of the tunneling layer and the antiferromagnetic layer to prepare a magnetoresistance device and realize the room temperature TAMR effect.

Description

A room temperature tunnel anisotropic magnetoresistance device and its preparation method

technical field

The invention relates to a room temperature tunnel anisotropic magnetoresistance device and a preparation method thereof.

Background technique

Tunneling anisotropic magnetoresistance (TAMR) effect is a very important physical phenomenon in spintronics, which mainly describes the anisotropic magnetoresistance generated in the tunneling structure of a single ferromagnetic layer. Different from the traditional tunnel junction composed of two layers of ferromagnetic semiconductors inserted into the tunneling barrier layer, this kind of device that relies on the strong orbital coupling in the single ferromagnetic layer to realize the injection and detection of spin-polarized current is more conducive to The post-processing technology, as well as the rich physical phenomena and potential application value it exhibits, have opened up a new branch of spintronics research. Since this phenomenon was discovered in the (Ga,Mn)As/alumina/Au system in 2004, it has aroused extensive research interest. Recently, Park et al. reported for the first time the TAMR effect based on antiferromagnetic materials, making the application of antiferromagnetic materials shift from traditional pinning layers to functional layers with rich physical connotations, which is of great significance for the development of antiferromagnetic spintronics. However, so far, all TAMR signals are measured at low temperature (<100K), and are mainly concentrated in in-plane magnetized ferromagnetic materials, which limits the practical application process.

Contents of the invention

The object of the present invention is to provide a room temperature tunnel anisotropic magnetoresistance device and a preparation method thereof.

The structure of the room-temperature tunnel anisotropic magnetoresistance device provided by the present invention sequentially includes: a substrate, a bottom electrode, a ferromagnetic layer (FM), an antiferromagnetic layer, a tunneling layer, and a top electrode; the ferromagnetic layer consists of A perpendicular magnetization film is formed, and the antiferromagnetic layer is formed of a Mn-based alloy.

Wherein, the perpendicular magnetization film constituting the ferromagnetic layer includes perpendicular magnetization [Co/Pt] _n , [Co/Pd] _n , [Co/Ni] _n multilayer films (n=1-10).

In the [Co/Pt] _n multilayer film, the thickness of each Co layer is 0.3nm-0.8nm, and the thickness of each Pt layer is 0.8nm-1.5nm.

In the [Co/Pd] _n multilayer film, the thickness of each Co layer is 0.3nm~0.8nm, and the thickness of each Pd layer is 0.8nm~1.5nm.

In the [Co/Ni] _n multilayer film, the thickness of each Co layer is 0.3nm~0.8nm, and the thickness of each Ni layer is 0.8nm~1.5nm.

The Mn alloy includes IrMn, FeMn and the like.

The thickness of the antiferromagnetic layer may be 2 nm to 6 nm.

The tunneling layer is made of MgO or Al ₂ O ₃ , and its thickness may be 1.5nm-2.5nm. Among them, Al ₂ O ₃ is prepared by magnetron sputtering, electron beam evaporation, plasma oxidation and natural oxidation of Al; MgO is prepared by magnetron sputtering and electron beam evaporation.

The bottom electrode and the top electrode are Pt electrodes.

The substrate is Si(100)/SiO ₂ , wherein the thickness of SiO ₂ is 300-500nm.

The method for preparing the room-temperature tunnel anisotropic magnetoresistance device includes the following steps: sequentially depositing a bottom electrode, a ferromagnetic layer (FM), an antiferromagnetic layer, a tunneling layer and a top electrode on a substrate.

Subsequently, the multilayer film is processed into a tunnel junction with a size of 5×3 μm ² ~100×60 μm ² through ultraviolet exposure, argon ion etching and metal lift-off method, and two wires are drawn from the bottom electrode and the top electrode to perform magnetoresistance. test.

The present invention utilizes the exchange coupling effect of the vertically magnetized ferromagnetic layer FM on one side of the tunneling layer and the antiferromagnetic layer IrMn to prepare a magnetoresistive device, and utilizes the higher thermal stability of the vertical exchange coupling effect and the thickness of the antiferromagnetic layer It is regulated to realize the TAMR effect with spin valve signal at room temperature. The magnetoresistance value of the device can be regulated by changing the thickness of the antiferromagnetic layer.

Detailed ways

The present invention will be described below through specific examples, but the present invention is not limited thereto.

The experimental methods described in the following examples, unless otherwise specified, are conventional methods; the reagents and materials, unless otherwise specified, can be obtained from commercial sources.

Example 1: Preparation of magnetic tunnel junction with Si/SiO ₂ /Pt/[Co/Pt] ₄ /Co/IrMn/Al ₂ O ₃ /Pt structure

The Pt/[Co/Pt] ₄ /Co/IrMn/Al ₂ O ₃ /Pt multilayer film structure is deposited on the Si/SiO ₂ substrate by magnetron sputtering. In this structure, [Co/Pt] ₄ /Co It is a ferromagnetic layer, the thickness of Co is 0.5nm, the thickness of Pt is 1nm, the thickness of antiferromagnetic layer IrMn is 2~6nm, and the thickness of tunneling layer Al ₂ O ₃ is 2nm. The prepared multilayer film has a clear and smooth interface, good adhesion and good vertical easy magnetization characteristics. Subsequently, the multilayer film is processed into a tunnel junction with a size of 5×3 μm ² ~100×60 μm ² through ultraviolet exposure, argon ion etching and metal lift-off method, and the bottom electrode (Pt) and the top electrode (Pt) are respectively drawn out. Two wires are tested for magnetoresistance.

The magnetoresistance test results of PPMS (Comprehensive Physical Properties Testing System) at room temperature show that when the direction of the magnetic field is perpendicular to the surface of the film, as the magnetic field changes from +1T to -1T and then to +1T, the measured resistance changes to a high resistance state (+ 1T) → low resistance state (-1T) → high resistance state (+1T); when the magnetic field direction is parallel to the surface of the film, the magnetoresistance change of the spin valve-like signal is obtained by testing, that is, the magnetic field is from +1T to -1T, and the test The resulting resistance change is high resistance state (+1T) → low resistance state (~0T) → high resistance state (-1T). The occurrence of this phenomenon is mainly due to the exchange spring effect of the ferromagnetic layer [Co/Pt] ₄ /Co and the antiferromagnetic layer IrMn, so that the reversal of the magnetic moment of the perpendicularly magnetized ferromagnetic layer drives the partial rotation of the magnetic moment of the antiferromagnetic layer. When the thickness of antiferromagnetic IrMn is 6nm, the TAMR value (tunnel anisotropic magnetoresistance value) in the vertical direction at room temperature measured by the multifunctional physical property measurement system (PPMS) is 0.236%, and the in-plane TAMR value is 0.070 %; when the thickness of IrMn is 4nm, the TAMR value in the vertical direction at room temperature is 0.051%; when the thickness of IrMn is 2nm, the TAMR value in the vertical direction at 150K is 0.027%, and there is no obvious TAMR signal at room temperature.

Example 2: Preparation of magnetic tunnel junction with Si/SiO ₂ /Pt/[Co/Pd] ₈ /Co/IrMn/MgO/Pt structure

The Pt/[Co/Pd] ₈ /Co/IrMn/MgO/Pt multilayer film structure is deposited on the Si/SiO ₂ substrate by electron beam evaporation, in which [Co/Pd] ₈ /Co is ferromagnetic layer, the thickness of Co is 0.3nm, the thickness of Pd is 1.2nm, the thickness of antiferromagnetic layer IrMn is 2~6nm, and the thickness of tunneling layer MgO is 2nm. The prepared multilayer film has a clear and smooth interface, good adhesion and good vertical easy magnetization characteristics. Subsequently, the multilayer film is processed into a tunnel junction with a size of 5×3 μm ² ~100×60 μm ² through ultraviolet exposure, argon ion etching and metal lift-off method, and two wires are drawn from the bottom electrode and the top electrode to perform magnetoresistance. test.

The test results of PPMS magnetoresistance at room temperature show that when the magnetic field is perpendicular to the surface of the film, as the magnetic field changes from +1T to -1T to +1T, the measured resistance changes from a high resistance state (+1T) to a low resistance state ( -1T) → high resistance state (+1T); when the magnetic field direction is parallel to the surface of the film, the magnetoresistance change of the spin valve-like signal is obtained in the test, that is, the magnetic field is from +1T to -1T, and the resistance change obtained by the test is high resistance state (+1T) → low resistance state (~0T) → high resistance state (-1T). When the thickness of antiferromagnetic IrMn is 6nm, the TAMR value in the vertical direction at room temperature is 5.32%, and the TAMR value in the plane is 1.89%; when the thickness of IrMn is 4nm, the TAMR value in the vertical direction at room temperature is 4.05%; When the thickness is 2nm, the TAMR value in the vertical direction at room temperature is 2.48%.

Claims (10)

1. A room temperature tunnel anisotropic magnetoresistance device, its structure comprises successively: substrate, bottom electrode, ferromagnetic layer, antiferromagnetic layer, tunneling layer and top electrode; Wherein, described ferromagnetic layer is made of perpendicular magnetization The antiferromagnetic layer is composed of a Mn-based alloy. 2. The room temperature tunnel anisotropic magnetoresistance device according to claim 1, characterized in that: the perpendicular magnetization film is selected from any of the following multilayer films: [Co/Pt] _n , [Co/Pd] _n and [Co/Ni] _n , where n=1~10. 3. room temperature tunnel anisotropic magnetoresistance device according to claim 2, is characterized in that: in described [Co/Pt] _n multilayer film, the thickness of each Co layer is 0.3nm～0.8nm, each Pt The thickness of the layer is 0.8nm~1.5nm; In the [Co/Pd] _n multilayer film, the thickness of each Co layer is 0.3nm~0.8nm, and the thickness of each Pd layer is 0.8nm~1.5nm; In the [Co/Ni] _n multilayer film, the thickness of each Co layer is 0.3nm~0.8nm, and the thickness of each Ni layer is 0.8nm~1.5nm. 4. The room temperature tunnel anisotropic magnetoresistance device according to any one of claims 1-3, characterized in that: the thickness of the antiferromagnetic layer is 2nm~6nm. 5. The room temperature tunnel anisotropic magnetoresistance device according to any one of claims 1-4, characterized in that the Mn-based alloy includes IrMn and FeMn. 6. The room temperature tunnel anisotropic magnetoresistance device according to any one of claims 1-5, _{characterized in that: the tunneling layer is made of MgO or Al2O3 ,} and the thickness of the tunneling layer is 1.5nm~2.5nm. 7. The room temperature tunnel anisotropic magnetoresistance device according to claim 6, characterized in that: said Al ₂ O ₃ is prepared by any one of the following methods: magnetron sputtering, electron beam evaporation, Al plasma Bulk oxidation and Al natural oxidation; the MgO is prepared by magnetron sputtering or electron beam evaporation. 8 . The room temperature tunnel anisotropic magnetoresistance device according to claim 1 , wherein both the bottom electrode and the top electrode are Pt electrodes. 9. The room temperature tunnel anisotropic magnetoresistance device according to any one of claims 1-8, characterized in that: the substrate is Si(100)/SiO ₂ , wherein the thickness of SiO ₂ is 300-500nm . 10. The method for preparing the room temperature tunnel anisotropic magnetoresistance device described in any one of claims 1-9, comprising the steps of: depositing sequentially on the substrate: bottom electrode, ferromagnetic layer, antiferromagnetic layer, tunneling layer and top electrode.