JP3517039B2 - Magnetic element - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a magnetic element.

[0002]

2. Description of the Related Art Recently, thermal or photoinduced magnetic coupling has been observed in an artificial lattice film of a magnetic substance and a semiconductor (J. Magn. M.
agn. Mater. 114 (1992) L6, Phys. Rev. Lett. 71 (19
93) 185, Phys. Rev. Lett. 73 (1994) 340, Jpn. J. A.
ppl. Phys. 33 (1994) L1672).

In this photo-induced magnetic coupling, the magnetic coupling state between the first and second ferromagnetic layers laminated via the semiconductor layer changes the carrier concentration of the semiconductor layer by thermal excitation or photoexcitation by light irradiation. It is believed to be induced by.

In this case, if the distinction between the effect of heating by light irradiation and the unique effect of photoexcitation is not discriminated, the switching speed becomes a problem if it is due to thermal excitation. Further, for example, a laser optical system is required to switch the direction of magnetization between exchange magnetic coupling between magnetic layers to ferromagnetic and antiferromagnetic coupling.

[0005]

As described above, in the conventional magnetic element using the photo-induced magnetic coupling, the light irradiation is indispensable, and the optical system is inevitably accompanied, and the miniaturization of the entire device is required. There's a problem. Further, if heating is required, there remains a problem in responsiveness. The present invention has been made in consideration of the above points, and an object thereof is to provide a magnetic element capable of controlling magnetic coupling without using an optical system.

[0006]

The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object, and as a result, by changing the potential of the dielectric layer interposed between the ferromagnetic layers, the magnetization of this ferromagnetic layer is changed. It was found that the orientation can be controlled to be antiparallel or parallel.

That is, according to the present invention, a laminated film having a dielectric layer interposed between a first conductive ferromagnetic layer and a second conductive ferromagnetic layer; and a potential of the dielectric layer is controlled. And a potential control means for changing the magnetic coupling state of the first and second conductive ferromagnetic layers.

The mechanism of magnetic coupling between magnetic layers via a conductive non-magnetic layer is generally considered as follows. The spins of the conduction electrons in the nonmagnetic layer interact with the spins of the magnetic atoms in the ferromagnetic layer, and this interaction induces a spin density distribution due to the conduction electrons in the nonmagnetic layer, and the total magnetic energy of the magnetic layer and the nonmagnetic layer. To determine the relative direction of magnetization of the magnetic layer. Therefore, the relative direction of magnetization is governed by how the spin density distribution stands in the nonmagnetic layer, and strongly depends on the thickness of the nonmagnetic layer and the concentration of conduction electrons. It is a well-known fact that magnetic coupling between magnetic layers depends on the thickness of the non-magnetic layer, and it is a well-known fact that it depends on the concentration of conduction electrons. This is consistent with the observed thermal or photoinduced magnetic coupling in the film. What is important is that the spin density distribution in the nonmagnetic layer conveys information on the magnetization directions of the ferromagnetic layers on both sides that are joined to the nonmagnetic layer. Therefore, the magnetic coupling can be controlled by artificially changing the transmitted content.

In the present invention, the potential barrier of conduction electrons is formed between the ferromagnetic layers, and the height of the potential barrier is changed to control the transmission content of the magnetization information. Since the height of the potential barrier can be controlled by an external electric circuit, the function of the field effect magnetic switching element can be exerted.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a conceptual diagram of the magnetic element of the present invention. Between the first conductive ferromagnetic layer (1) and the second conductive ferromagnetic layer (2), a potential control means (4) capable of controlling the applied voltage, for example, a variable voltage DC voltage source is connected, By changing the voltage, the first and second tunnel insulating films are formed.
The potential barrier of the dielectric layer (3) between the conductive ferromagnetic layers (1) and (2) is changed. This change changes the transmission of magnetization information by conduction electrons, so that the magnetization directions of the first and second conductive ferromagnetic layers (1) and (2) can be made parallel or antiparallel.

Examples of the element constituting the ferromagnetic layer of the present invention include Co, Fe, Ni or alloys thereof, but are not particularly limited as long as they are conductive ferromagnetic materials. The thickness t _M is preferably 0.2 nm ≦ t _M ≦ 10 nm, more preferably 0.4 nm ≦ t _M ≦ 8 nm.

The constituent material of the dielectric layer of the present invention is Al ₂ O.
Insulators such as ₃ , SiO ₂ ; intrinsic semiconductors such as Si and Ge; compound semiconductors such as AlP, AlAs and GaAs; and F
A semiconductor such as an eSi alloy may be used, but the dielectric is not particularly limited. The thickness t _D is 0.1 nm ≦ t _D ≦
5 nm, and more preferably 0.1 nm ≦ t _D 2 nm. Although the basic unit has three layers, a larger number of layers may be added. Various constituent films are prepared by molecular beam epitaxy (MBE) method, ultra-high vacuum sputtering method, etc., as well as RF magnetron sputtering method, ion beam sputtering method, vacuum deposition method, etc., and initial vacuum degree is 10 ⁻⁷ Tor.
It can also be produced by a normal thin film forming technique of r or less. A so-called artificial lattice may be formed. The film shape can be formed by lithography, chemical etching, or the like.

As shown in FIG. 2, conductive nonmagnetic layers (5) and (6) may be formed on the surface of at least one of the dielectric layers. It is possible to improve the uniformity of the potential of the dielectric layer and the magnetic coupling between the ferromagnetic layers. In this case, the potential control means may be connected to the ferromagnetic layer or the non-magnetic layer.

As the elements constituting the non-magnetic layer of the present invention, for example, Cu, Al, Ag, Au, Pd, Pt, Cr, R
A simple substance such as u or Rh or an alloy containing them can be used. The thickness t _N of the nonmagnetic layer is t _N ≦ 10 nm,
It is more preferable that t _N ≦ 5 nm.

C is also used as an electrode layer on the surface of the ferromagnetic layer.
You may form a conductor layer, such as u, Au, and Ag. Less than,
The present invention will be described in detail with reference to examples. Example 1 In this example, Co is used for the ferromagnetic layers (1) and (2), Cu is used for the nonmagnetic layers (5) and (6), and SiO ₂ is used for the dielectric layer (3). To form a laminated film. First, 5 × 10 ^-7 To inside the chamber
After exhausting to rr, Ar was introduced up to 1 × 10 ⁻⁴ Torr, and sputtering was performed under the conditions of an acceleration voltage of sputtered Ar ions of 600 V and a beam current of 30 mA. As targets, Au, Co, Cu and SiO ₂ are prepared, and M
The gO (100) single crystal is used as the substrate (10). First M
Au as a buffer layer and an electrode on a gO (100) substrate
Layers of 10 nm, then Co layer of 2 nm, Cu layer of 0.5 nm, SiO ₂ layer of 0.5 nm, and Cu layer of 0.5 nm.
nm and Co layers were alternately laminated in the order of 2 nm, and finally, an Au layer was laminated to 10 nm so as to also serve as an antirust layer and an electrode. In this way (Au10nm / Co2nm / Cu0.5n
m / SiO ₂ 0.5 nm / Cu 0.5 nm / Co ₂ nm
/ Au 10 nm) / MgO (100) laminated film was formed (FIG. 3).

An applied potential V of 0-
The magnetic characteristics were measured while changing to 0.5 [V]. V in Figure 4
The results when = 0 and 0.4 [V] are shown. Magnetic characteristic is V
The measurement was performed by applying an in-plane magnetic field using an SM (Vibrating Sample Magnetometer). From the result of FIG. 4, when the magnetic coupling between Co layers is V = 0 [V], it is ferromagnetic, and V = 0.4.
It was found that antiferromagnetic coupling occurs at [V]. (Example 2) A method similar to that of Example 1 was used (Au1).
0 nm / Co ₂ nm / Cu 0.5 nm / SiO ₂ 0.5
nm / Cu 0.5 nm / Permalloy 2 nm / Au 10 n
The magnetic properties for m) / MgO (100) are shown in FIG. From FIG. 5, the magnetic coupling between Co and the permalloy layer is V = 0.
It was found that the coupling was ferromagnetic at [V] and antiferromagnetic at V = 0.4 [V]. (Example 3) The same method as in Example 1 was used (Au1).
0 nm / Co ₂ nm / Cu 0.5 nm / Al ₂ O ₃ 0.
5 nm / Cu 0.5 nm / Co 2 nm / Au 10 nm)
The magnetic characteristics of / MgO (100) are shown in FIG.
From FIG. 6, it was found that the magnetic coupling between the Co layers was ferromagnetic when V = 0 [V] and antiferromagnetic when V = 0.4 [V]. (Example 4) The same method as in Example 1 was used (Au1).
0 nm / Co ₂ nm / Cu 0.5 nm / Al ₂ O ₃ 0.
5nm / Cu 0.5nm / Permalloy 2nm / Au10
(nm) / MgO (100) magnetic properties are shown in FIG. From FIG. 7, the magnetic coupling between Co and the permalloy layer is V =
It was found that the coupling was ferromagnetic at 0 [V] and antiferromagnetic at V = 0.4 [V]. (Example 5) The same method as in Example 1 was used (Au1).
0 nm / Co ₂ nm / Cu 0.5 nm / Al ₂ O ₃ 0.
5 nm / Cu 0.5 nm / Permalloy 2 nm / Cu 0.
5 nm) / Al ₂ O ₃ 0.5 nm / Cu 0.5 nm / C
FIG. 8 shows a device schematic view and magnetic characteristics of (2 nm / Au 10 nm) MgO (100). It can be seen from FIG. 8 that the magnetic coupling between Co and the permalloy layer is ferromagnetic when V ₁ = V ₂ = 0 [V] and antiferromagnetic when V ₁ = V ₂ = 0.4 [V]. Do you get it. Note that V ₁ = V ₂ is the voltage between the Au layer and the permalloy layer.

[0017]

As described above, according to the present invention, it is possible to provide a magnetic element that realizes magnetic coupling control that does not require the action of an external magnetic field or a laser optical system. Therefore, it can be applied to an electrically writable magnetic recording medium (reading may use the magnetoresistive effect or the Kerr effect as in the conventional magneto-optical recording medium).

[Brief description of drawings]

FIG. 1 is a conceptual diagram of the present invention.

FIG. 2 is a conceptual diagram of the present invention.

FIG. 3 is a conceptual diagram of the present invention.

FIG. 4 is a characteristic diagram of the present invention.

FIG. 5 is a characteristic diagram of the present invention.

FIG. 6 is a characteristic diagram of the present invention.

FIG. 7 is a characteristic diagram of the present invention.

FIG. 8 is a characteristic diagram of the present invention.

[Explanation of symbols]

1 ... First conductive ferromagnetic layer 2 ... second conductive ferromagnetic layer 3 ... Dielectric layer 5, 6 ... Conductive non-magnetic layer

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Claims (2)

(57) [Claims] 1. A laminated film comprising a first conductive ferromagnetic layer, a second conductive ferromagnetic layer, and a dielectric layer interposed between these conductive ferromagnetic layers ; said dielectric layer. At least one of
A conductive non-magnetic layer provided on the surface; and a potential control means for controlling the potential of the dielectric layer and changing the magnetic coupling state of the first and second conductive ferromagnetic layers. Characteristic magnetic element. 2. The magnetic element according to claim 1 , wherein the conductive nonmagnetic layer is provided on both surfaces of the dielectric layer.