CN108447982A - An information storage device with electric field non-volatile regulation of tunnel magnetoresistance - Google Patents

Abstract

The invention discloses a kind of information recording devices of the non-volatile regulation and control tunnel magneto resistance of the electric field for belonging to technical field of information storage；The information recording device has is sequentially overlapped the multi-layer compound film structure formed by bottom electrode layer, ferroelectric layer, seed layer, inverse ferric magnetosphere, ferromagnetic pinning layer, non magnetic barrier layer, ferromagnetic free layer, protective layer and top electrode layer.Ferromagnetic pinning layer, non magnetic barrier layer and ferromagnetic free layer constitute the magnetic tunnel junction sandwich structure with tunnel magneto resistance.Bottom electrode layer and seed layer apply electric field respectively as the positive and negative electrode of ferroelectric layer to it, and wherein direction of an electric field is perpendicular to ferroelectric layer.Ferroelectric layer rotates the magnetic moment orientation of ferromagnetic free layer to regulate and control tunnel magneto resistance under electric field action by magnetoelectric effect.Electric field can realize that information is written to the present invention with the high and low configuration of Effective Regulation tunnel magneto resistance in practical applications, have many advantages, such as room temperature, zero magnetic field, low-power consumption and non-volatile.

Description

An information storage device with electric field non-volatile regulation of tunnel magnetoresistance

technical field

The invention relates to an information storage device for controlling tunnel magnetoresistance with non-volatile electric field, and belongs to the technical field of information storage.

Background technique

Magnetic random access memory is a storage device with high storage density, fast read and write, and non-volatility. Its core storage unit is a magnetic tunnel junction. The basic working principle of MRAM information writing is to change the mutual orientation of the magnetization states of the ferromagnetic free layer and the ferromagnetic pinned layer by rotating the magnetic moment of the ferromagnetic free layer, thereby generating two high and low states in the magnetic tunnel junction. Tunneling magnetoresistance states for information storage. At present, the information writing of the magnetic random access memory uses a magnetic field or a spin transfer torque, which requires a large current density, and thus consumes a lot of power for writing. Using electric field to control magnetism and tunnel magnetoresistance to write information can effectively reduce power consumption and has great potential application prospects. Nowadays, there are problems such as low temperature, need for magnetic field assistance, and volatility in the regulation of tunnel magnetoresistance by electric field.

In order to overcome the shortcomings of low temperature, need for magnetic field assistance, and volatility, a structure of growing magnetic tunnel junctions on ferroelectric substrates is proposed. The write operation does not require the assistance of an external magnetic field, thereby realizing the non-volatile regulation of the tunnel magnetoresistance by the electric field at room temperature and zero magnetic field, and at the same time reducing power consumption.

Contents of the invention

The object of the present invention is to propose an information storage device for regulating tunnel magnetoresistance with non-volatile electric field, characterized in that the information storage device for non-volatile regulating tunnel magnetoresistance with electric field has a multi-layer composite film structure, and the The multilayer composite thin film structure is formed by stacking bottom electrode layer, ferroelectric layer, seed layer, antiferromagnetic layer, ferromagnetic pinning layer, nonmagnetic barrier layer, ferromagnetic free layer, protective layer and top electrode layer; The ferroelectric layer is formed on the bottom electrode layer; the seed layer is formed on the ferroelectric layer; the antiferromagnetic layer is formed on the seed layer for interfacial coupling to the ferromagnetic pinning layer A pinning effect is generated; the ferromagnetic pinning layer is formed on the antiferromagnetic layer, and its magnetic moment is pinned and fixed by the antiferromagnetic layer; the nonmagnetic barrier layer is formed on the ferromagnetic pinning layer The ferromagnetic free layer is formed on the nonmagnetic barrier layer; the protective layer is formed on the ferromagnetic free layer to protect the ferromagnetic free layer from oxidation; the top electrode layer is formed on the above the protective layer.

The ferromagnetic pinned layer, the nonmagnetic barrier layer and the ferromagnetic free layer constitute a magnetic tunnel junction sandwich structure with tunnel magnetoresistance.

The bottom electrode layer and the seed layer are respectively used as the positive and negative electrodes of the ferroelectric layer, and an electric field is applied to the ferroelectric layer, and the direction of the electric field is perpendicular to the ferroelectric layer; The orientation of the magnetic moment of the layer is used to make the tunnel magnetoresistance of the magnetic tunnel junction non-volatile.

The seed layer and the top electrode layer are used as electrodes of the magnetic tunnel junction to measure the tunnel magnetoresistance.

The ferroelectric layer can generate non-volatile strain under the action of positive and negative asymmetric electric fields at room temperature.

The beneficial effect of the invention is that the information storage device grows the magnetic tunnel junction on the ferroelectric layer, and uses the magnetoelectric coupling effect to realize the non-volatile control of the tunnel magnetoresistance by the electric field at room temperature and zero magnetic field; it overcomes the existing There are problems such as low temperature, need for magnetic field assistance, and volatility in the regulation of tunnel magnetoresistance by electric field. The invention operates at room temperature, does not require external magnetic field assistance, is non-volatile, and has low power consumption.

Description of drawings

Fig. 1 is a schematic structural diagram of an information storage device for non-volatile control of tunnel magnetoresistance by an electric field.

Fig. 2 is a non-volatile strain curve of the ferroelectric layer.

Figure 3 shows the regulation behavior of the tunnel magnetoresistance curve under different electric fields.

Figure 4 shows the variation of tunnel magnetoresistance with electric field at room temperature and zero magnetic field.

Figure 5 shows the non-volatile control of the high and low resistance states of tunnel magnetoresistance by pulsed electric field at room temperature and zero magnetic field.

Fig. 6 is a schematic diagram of the working principle of electric field non-volatile control tunnel magnetoresistance.

Explanation of reference signs: 1-bottom electrode layer, 2-ferroelectric layer, 3-seed layer, 4-antiferromagnetic layer, 5-ferromagnetic pinning layer, 6-nonmagnetic barrier layer, 7-ferromagnetic free layer, 8-protective layer, 9-top electrode layer.

Detailed ways

The present invention proposes an information storage device for controlling tunnel magnetoresistance with non-volatile electric field. Its structure is shown in FIG. A multi-layer composite film structure formed by sequentially stacking the magnetic pinning layer 5, the non-magnetic barrier layer 6, the ferromagnetic free layer 7, the protective layer 8 and the top electrode layer 9.

The bottom electrode layer 1 and the seed layer 3 serve as positive and negative electrodes of the ferroelectric layer 2 respectively, and an electric field is applied thereto, wherein the direction of the electric field is perpendicular to the ferroelectric layer 2 . The exchange bias effect generated by the interface coupling between the antiferromagnetic layer 4 and the ferromagnetic pinning layer 5 produces a pinning effect on the ferromagnetic pinning layer 5, so that the magnetic moment of the ferromagnetic pinning layer 5 is fixed at zero magnetic field, Cannot be rotated by an electric field. The ferromagnetic pinning layer 5, the nonmagnetic barrier layer 6 and the ferromagnetic free layer 7 constitute a magnetic tunnel junction sandwich structure with tunnel magnetoresistance. The protection layer 8 is used to protect the ferromagnetic free layer 7 from being oxidized. The seed layer 3 and the top electrode layer 9 serve as electrodes of the magnetic tunnel junction to measure the tunnel magnetoresistance. The ferroelectric layer 4 can generate nonvolatile strain under the action of the electric field, and the strain is transmitted to the magnetic tunnel junction on it, and the magnetic moment orientation of the ferromagnetic free layer 7 is rotated by the magnetoelectric coupling effect so that the magnetic tunnel junction The tunneling magnetoresistance occurs in non-volatile regulation.

The information storage device of the electric field non-volatile control tunneling magnetoresistance proposed by the present invention, its preparation process can adopt the magnetron sputtering method, including the following steps:

(1) purchase the crystal of 30% lead magnesium niobate titanate (hereinafter referred to as PMN-PT), and process it into a ferroelectric layer 2, so that the size of the ferroelectric layer is long (along [100] direction) ×width (along [01-1] direction)×thickness (along [011] direction) is equal to 10×10×0.5 ^mm3 , and can be changed reasonably according to actual needs. Then perform single-sided (011) surface polishing, requiring a roughness of less than 1 nanometer.

(2) A 300 nm gold layer (Au) was sputtered on the unpolished surface of the ferroelectric substrate as the bottom electrode by magnetron sputtering method.

(3) Using the magnetron sputtering method, the seed layer 3, the antiferromagnetic layer 4, the ferromagnetic pinning layer 5, the nonmagnetic barrier layer 6, and the ferromagnetic free layer 7 are sequentially sputtered on the polished surface of the ferroelectric substrate and protective layer 8. The antiferromagnetic layer 4 is made of iridium-manganese alloy (Ir ₂₀ Mn ₈₀ ) and artificial antiferromagnetic structure, and the ferromagnetic pinned layer 5 and ferromagnetic free layer 7 are made of ferromagnetic metal cobalt-iron-boron alloy (Co ₄₀ Fe ₄₀ B ₂₀ ) , The non-magnetic barrier layer 6 is made of magnesium oxide (MgO). The process parameters of magnetron sputtering are: use an ultra-high vacuum system at room temperature, pump the background vacuum to 10 ^-6 Pa, and have a magnetic field of about 100 Oersted along the [100] crystal direction of PMN-PT during the growth process To determine the pinning direction of the antiferromagnetic layer.

(4) The grown sample is annealed in an annealing furnace in a vacuum environment with a magnetic field to crystallize the non-magnetic barrier layer 6 and increase the tunnel magnetoresistance. During the annealing process, the magnetic field is 8000 Oersted, and the direction of the magnetic field is consistent with the direction of the magnetic field applied during the growth of the sample, along the [100] crystal direction of PMN-PT. The annealing temperature is 360 degrees Celsius, and the annealing time is 1 hour.

(5) The annealed sample was microfabricated into a circular structure with a diameter of 10 microns by photolithography, and then the top electrode 9 was grown by magnetron sputtering.

Example 1,

A multiferroic composite structure with electric field non-volatile regulation of tunnel magnetoresistance was prepared, as shown in Figure 1.

The purchase composition is 30% lead magnesium niobate lead titanate crystal, and the crystal is processed into a ferroelectric layer 2, so that the size of the ferroelectric layer base is long (along [100] direction) * wide (along [01-1] direction)×thickness (along [011] direction) is equal to 10×10× ^0.5mm3 . Then perform single-sided (011) surface polishing, requiring a roughness of less than 1 nanometer. A 300 nm gold layer (Au) was sputtered on the unpolished surface of the ferroelectric substrate as the bottom electrode layer 1 by using the magnetron sputtering method. As shown in Fig. 2, the strain curves of the [011]-oriented PMN-PT ferroelectric layer exhibited non-volatility at electric fields of 8 kV/cm and −1.6 kV/cm, and there were two strains at zero electric field state. The materials for each layer are selected as follows:

The seed layer 3 uses, but is not limited to, 5nm tantalum (Ta) and 5nm ruthenium (Ru).

The antiferromagnetic layer 4 is preferably, but not limited to, iridium manganese alloy (Ir ₂₀ Mn ₈₀ ) and artificial antiferromagnetic structure cobalt iron/ruthenium/cobalt iron boron (Co ₇₀ Fe ₃₀ /Ru/Co ₄₀ Fe ₄₀ B ₂₀ ).

The ferromagnetic pinned layer 5 and the ferromagnetic free layer 7 are made of ferromagnetic cobalt-iron-boron alloy (Co ₄₀ Fe ₄₀ B ₂₀ ), both of which have a thickness of 2.6 nanometers.

The non-magnetic barrier layer 6 is preferably but not limited to magnesium oxide (MgO), and its thickness is 2.3 nanometers.

The protective layer 8 is made of 5nm tantalum (Ta) and 7nm ruthenium (Ru).

After microfabrication, the top electrode layer 9 adopts 10 nanometers of titanium (Ti) and 60 nanometers of gold (Au).

Example 2,

Measuring the electric-field-regulated tunneling magnetoresistance performance of the multiferroic composite structure prepared above: the transport properties of the above-prepared samples were measured using the EM3 electromagnet system of Beijing Oriental Morning View Technology Co., Ltd., and all measurements were carried out at room temperature. Tunneling magnetoresistance curves shown in Fig. 3 show a distinctly different behavior at +0 kV/cm after applying an electric field of 8 kV/cm and at -0 kV/cm after applying -1.6 kV/cm , and its tunnel magnetoresistance is as high as 235%. As shown by the arrows in Figure 3, under zero magnetic field, there are two different tunnel magnetoresistance states at 0 kV/cm, which indicates that this is a non-volatile regulation of electric field on tunnel magnetoresistance under zero magnetic field, It can control the tunnel magnetoresistance up to about 108%.

As shown in Figure 4, under zero magnetic field, when the electric field scans for a week, it gradually changes from 0 kV/cm to 8 kV/cm, then gradually decreases to 0 kV/cm, and then increases to - 1.6 kV/cm, and then gradually decreased to 0 kV/cm, it was found that the tunnel magnetoresistance showed a hysteresis characteristic, and there were two tunnel magnetoresistance states under zero electric field, which showed that the electric field had no effect on tunnel magnetoresistance regulation. Volatile.

Under zero magnetic field, by using positive and negative pulsed electric fields with electric field strengths of 8 kV/cm and -1.6 kV/cm, the regulation behavior of TMR with obvious high and low resistance states can be achieved, as shown in Figure 5 , which is of great significance for practical applications.

Example 3,

FIG. 6 is a schematic diagram of the working principle of the electric field non-volatile control tunnel magnetoresistance. In Fig. 6, after applying a pulsed electric field of -1.6 kV/cm, the strain generated by it can rotate the magnetic moment of the ferromagnetic free layer 7 at -0 kV/cm, so that the ferromagnetic free layer in the magnetic tunnel junction can be 7 and the relative orientation of the magnetic moments of the ferromagnetic pinning layer 5 are adjusted from the antiparallel state to the perpendicular state, thus forming a low resistance state; and after applying a pulsed electric field of 8 kV/cm, the ferromagnetic The magnetic moment of the free layer 7 can be rotated back to the initial state, so that the relative orientation of the magnetic moments of the ferromagnetic free layer 7 and the ferromagnetic pinned layer 5 in the magnetic tunnel junction can be adjusted from a perpendicular state to an antiparallel state, forming a high resistance state . Therefore, applying positive and negative pulsed electric fields of 8 kV/cm and -1.6 kV/cm can make the relative orientation of the magnetic moments of the ferromagnetic free layer 7 and the ferromagnetic pinned layer 5 reciprocate between the antiparallel state and the perpendicular state Regulation, so as to realize the non-volatile regulation of tunnel magnetoresistance by electric field at room temperature and zero magnetic field.

Claims (5)

1. a kind of information recording device of the non-volatile regulation and control tunnel magneto resistance of electric field, which is characterized in that the electric field is non-volatile Property regulation and control tunnel magneto resistance information recording device have multi-layer compound film structure, the multi-layer compound film structure by bottom electricity Pole layer, ferroelectric layer, seed layer, inverse ferric magnetosphere, ferromagnetic pinning layer, non magnetic barrier layer, ferromagnetic free layer, protective layer and top electrode Layer is sequentially overlapped to be formed；The specifically described ferroelectric layer is formed on bottom electrode layer；The seed layer is formed on ferroelectric layer； The inverse ferric magnetosphere is formed on seed layer, for generating pinning effect to ferromagnetic pinning layer by interface coupling；The iron Magnetic pinning layer is formed on inverse ferric magnetosphere, and magnetic moment is fixed by inverse ferric magnetosphere pinning；The non magnetic barrier layer is formed in On ferromagnetic pinning layer；The ferromagnetic free layer is formed on non magnetic barrier layer；The protective layer is formed in ferromagnetic freedom On layer, to protect the ferromagnetic free layer not oxidized；The top electrode layer is formed on the protective layer.

2. a kind of information recording device of the non-volatile regulation and control tunnel magneto resistance of electric field, feature exist according to claim 1 In the ferromagnetic pinning layer, non magnetic barrier layer and ferromagnetic free layer constitute magnetic tunnel junction Sanming City with tunnel magneto resistance Control structure.

3. a kind of information recording device of the non-volatile regulation and control tunnel magneto resistance of electric field, feature exist according to claim 1 In the bottom electrode layer and seed layer apply electric field, direction of an electric field hangs down respectively as the positive and negative electrode of ferroelectric layer to ferroelectric layer Directly in ferroelectric layer；Ferroelectric layer rotates the magnetic moment orientation of ferromagnetic free layer under electric field action by magnetoelectric effect, so that Non-volatile regulation and control occur for the tunnel magneto resistance of magnetic tunnel junction.

4. a kind of information recording device of the non-volatile regulation and control tunnel magneto resistance of electric field, feature exist according to claim 1 In, the seed layer and top electrode layer as the electrode of magnetic tunnel junction to measure tunnel magneto resistance.

5. a kind of information recording device of the non-volatile regulation and control tunnel magneto resistance of electric field, feature exist according to claim 1 In the ferroelectric layer at room temperature, non-volatile strain can be generated under the action of positive and negative asymmetric electric field.