JP3216448B2 - Amplifying element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a memory element and an amplification element utilizing a magnetoresistance effect.

[0002]

2. Description of the Related Art In recent years, [Fe / Cr] and [Co / Ru] artificial lattice films, which are antiferromagnetically coupled via a non-magnetic thin film of metal such as Cr or Ru, have a strong magnetic field (1 to 10 kOe). In Giant Magnetoresistance (Physical Review Letter 61, Section 2472 (1988);
Id.64 Section 2304 (1990) (Physical Review Letter Vol.
61, p2472, 1988; Vol. 64, p2304, 1990)). A giant magnetoresistance effect was also found in a [Ni-Fe / Cu / Co] artificial lattice film using magnetic thin films Ni-Fe and Co separated by a non-magnetic metal thin film Cu and having no magnetic coupling but different coercive forces. , Room temperature applied magnetic field
An MR ratio of about 8% was obtained at 0.5 kOe (see Journal
Off Physical Society Off Shah 59 59 Page 3061 (1990)
(Journal of Physical Society of Japan Vol.59, p306
1, 1990)).

A memory device using such an artificial lattice magnetoresistive film as shown in FIG. 5 has been proposed (Japanese Patent Application H5-28748). This memory element is composed of an information reading section S composed of an artificial lattice magnetoresistive film, an information holding section M composed of a hard magnetic film, and an information recording section composed of magnetic field applying current lines R and R '. There is a disadvantage that there are many steps.

[0004]

According to the present invention, an artificial lattice magnetoresistive film has a structure in which an information holding portion and an information reading portion are also used. The use of the film enables a small memory element having a small information recording current and a large information reading output, and can also be used as an amplifying element if the usage is changed.

[0005]

According to the present invention, there is provided an artificial lattice film formed by laminating a magnetic film and a non-magnetic metal film having both information holding and reading functions, and an information provided in the vicinity thereof via an insulating film via an insulating film. In the artificial lattice film portion, the exchange coupling energy J between the magnetic films is adjusted by adjusting the non-magnetic metal film thickness to J <0, that is, for each magnetic layer. The energy is lower when the spin is antiparallel than when the spin is parallel, and the magnetic anisotropy energy K of the artificial lattice film satisfies K> | J |. When the direction of the magnetic field generated by passing a current and the direction of the easy axis of magnetization caused by K are substantially parallel to each other, and the external magnetic field H is increased from 0 to H> 0 as shown in FIG. Once the resistance of the artificial lattice film increases, the reversal magnetic field H After reaching the maximum, the resistance value decreases and becomes substantially the same resistance value as when H = 0 when the saturation magnetic field is equal to or higher than Hs. After that, when H is reduced, there is almost no change in resistance until H = 0, and the magnetic field is inverted to H When the magnetic field is increased in the <0 direction, the magnetoresistance change operation is symmetrical to the case of H> 0.

[0006]

The saturation magnetization of the magnetic layer of the artificial lattice film composed of the magnetic layers 1 and 2 and the non-magnetic layer is M _i (i = 1, 2), the exchange coupling energy through the non-magnetic layer is J ₁₂ , If the magnetic anisotropy energy is K _i (i = 1,2) and the external magnetic field is H, the energy E of this system is E = −1 / 2ΣHM _i cos φ _i −φJ ₁₂ cos (φ ₁ -φ ₂ ) +1 / 2ΣK _i sin ² φ _i ---- (1) However, as a simple example, a uniaxial anisotropy is assumed, where the direction of the applied magnetic field is the easy axis direction, the angle between the applied magnetic field direction and the magnetization of the magnetic layer is φ. This uniaxial anisotropy K can be given to a film by devising a film forming method. By appropriately adjusting the thickness of the non-magnetic film, J
<0, where the film generally exhibits a giant magnetoresistance effect. In equation (1), J <0 and K> | J |,
In addition, when both | J | and K are relatively small, the MR (magnetic resistance) curve in the easy axis direction of the artificial lattice film becomes a curve as shown in FIG. It is possible to show a large change in magnetoresistance in a magnetic field.

If this condition is not satisfied, for example, K <
When | J |, a large change in magnetoresistance cannot be obtained with a small magnetic field near the zero magnetic field. When J> 0, a so-called giant magnetoresistance effect cannot be obtained.

The basic structure of the artificial lattice film portion is [magnetic metal film / non-magnetic metal film / magnetic metal film].
Nonmagnetic metal film] may be laminated. The magnetic metal layer film may have the same composition or a different composition. However, since the composition may be essentially the same, compared to a conventional magnetoresistive element using a different coercive force that is not magnetically coupled, the sputtering may be performed. In the case of forming a film by the method, there is an advantage that only one kind of magnetic target can be used.

The mechanism by which the magnetoresistance change occurs is that when the magnetization direction between the magnetic layers is antiparallel, the magnetic scattering of electrons at the interface between the magnetic layer and the nonmagnetic layer increases and the resistance increases. When the resistance shows the maximum, the magnetization directions of the respective magnetic layers become substantially antiparallel, and when a sufficient magnetic field is applied, the magnetization directions of the respective magnetic layers become parallel to the magnetic field directions.

FIG. 2 shows an example of the element of the present invention, in which an electric current is applied to a metal conductor wire 1 provided on an insulating film 3 to saturate an artificial lattice film portion 2 composed of a magnetic film 2M and a nonmagnetic film 2N. Information is recorded by generating a magnetic field of Hs or more, and at the time of reading information, a magnetic field of a reversal magnetic field Hm or less shown in FIG. 1 is applied to the metal conductor wire, and the direction of the magnetic field is parallel to the direction of the information recording magnetic field. In the case, there is almost no resistance change of the artificial lattice film conductor,
In the case of antiparallel, information is read out due to a change in the resistance of the artificial lattice film conductor. Further, information reading may be performed by applying a pulse in which the direction of the magnetic field changes to the current line, and determining whether the resistance change of the artificial lattice film conductor at this time is + (increase) or-(decrease).

In the present invention, the hard magnetic film is not used as the magnetic film of the artificial lattice film portion, and the direction of the easy axis due to the magnetic anisotropy energy K of the artificial lattice film and the direction of the magnetic field generated by the metal conductor wire portion are parallel. And K> | J |
As a result, unlike the conventional antiferromagnetically-coupled artificial lattice film, the saturation magnetic field Hs of the artificial lattice film portion is small, so that the current flowing through the metal conductor wire portion can be suppressed to be small. It is. Also, in the present invention, the nonmagnetic metal film thickness of the artificial lattice film is adjusted so that the magnetic metal film is antiferromagnetically coupled so that a giant magnetoresistance effect can be obtained. The output at the time is also large.

A memory array can be obtained by arranging the memory elements in a matrix, forming a conductor line portion comprising two conductor lines, and arranging each memory element at the intersection of these lines. Can be

Further, the artificial lattice film portions exhibit different magnetoresistance change characteristics (that is, Hs and Hm are different).
Multiple types of building blocks [magnetic metal film / non-magnetic metal film /
Magnetic metal film] ^N (where N is the number of layers N ≧ 1) is obtained by using an artificial lattice film portion in which a plurality of blocks are laminated via a non-magnetic film provided for separating magnetic interaction between these constituent blocks. In addition, a configuration block in which information is recorded and a configuration block in which information is not recorded are generated according to the value of the recording current of the conductor wire, and a multiple memory element can be realized.

When used as an amplifying element, the element is initialized by passing a current that generates a magnetic field exceeding Hs into the conductor wire once, and a weak current proportional to the input voltage is applied to the conductor wire so that the current does not exceed Hm. A magnetic field is generated, and the amplified resistance is extracted by changing the magnetic resistance of the artificial lattice film portion in conjunction therewith.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The magnetic film of the superlattice film portion is liable to cause a change in magnetoresistance and needs to be a film with low magnetostriction. This is because, if the magnetostriction is practically large, a cause of noise and a variation in characteristics occur. It is also desirable that the crystal anisotropy of the crystal itself be small, and it is desirable that the magnetic anisotropy can be easily imparted using magnetic field evaporation, oblique evaporation, or a special substrate. Satisfying these conditions, magnetostriction
A material that exhibits soft magnetism at 10 ⁻⁵ or less and easily reverses magnetization at a low magnetic field is mainly composed of Ni _X Co _Y Fe _Z --- (2) with an atomic composition ratio of X = 0.6 to 0.9 and Y = 0. ~ 0.4, Z = 0 ~ 0.3 --- (2 ') Ni-rich soft magnetic film is desirable.
Ni _0.8 Co _0.10 Fe _0.10, a Ni _{0 .68} Co _0.2 Fe _0.12 mag. Although the soft magnetic properties are slightly inferior to these, the magnetostriction is still 10 ^-5.
In the following, Ni _{X '} Co _Y' Fe _{Z '} --- (3) is used as the main component, and the atomic composition ratio X' = 0 ~ 0.4, Y '= 0.2 ~ 0.95, Z = 0 ~ 0.5 --- (3') Co-rich magnetic film, typical of which is Co _0.7 N
i _0.1 Fe _0.2 , Co _0.61 Ni _{0.2 3} Fe _0.16 , Co _0.46 Fe _0.34 Ni _0.20
And so on. When the thickness of the magnetic layer is less than 1 nm, the soft magnetic properties of the artificial lattice film are slightly impaired, and when the thickness is more than 10 nm, the MR properties are deteriorated.

The non-magnetic metal film has a small reaction at the interface with the magnetic metal film and is hardly dissolved, and it is desirable that the interface between the magnetic metal film and the non-magnetic metal film is clear. It is necessary to couple the magnetic films antiferromagnetically,
Those satisfying these conditions include Cu, Ag, and Au.
Cu is particularly preferred for obtaining a particularly large magnetoresistance change.
When the thickness t of the nonmagnetic metal film is changed, the coupling energy J between the magnetic layers decreases while oscillating between positive and negative. J
Is negative and a large MR change is obtained when the artificial lattice film is formed by the sputtering method when t is around 0.9 nm and 2.0 nm. When t is around 0.9 nm, | J | K
In order to satisfy> | J |, K becomes large, and it becomes difficult to obtain a large MR change in a low magnetic field, which is the object of the present invention. Therefore, it is desirable that t is around 0.2 nm. And M
In an artificial lattice epitaxial film produced by a vapor deposition method using BE or the like, t
Is near 1.6nm, 2.0nm, 2.4nm and J is relatively negative | J |
And a large MR change is obtained. Therefore, t is 1.5 nm
To 2.5 nm is desirable. More specifically, at least K is 5 × 10 ⁴ erg in order to obtain the MR characteristic of the low magnetic field operation.
/ cc and | J | also needs to be less than this.

The artificial lattice film portion basically needs to have a configuration of [magnetic metal film / non-magnetic metal film / magnetic metal film], but the number of stacked [magnetic metal film / non-magnetic metal film] is too small. If the number is small, it is difficult to obtain a large change in magnetoresistance. Therefore, it is desirable that at least the number of layers be three or more. In addition, when used as an amplifying element, it is necessary to supply a current to the artificial lattice conductor part more than when used as a memory element, and it is also desirable that the number of layers be three or more.

When used as a multiple memory element, different combinations of the composition of the magnetic metal film may be selected from the above formulas (2) and (3), or the thickness of the magnetic metal film may be changed without changing the composition. K may be adjusted by changing the thickness, or J may be adjusted by changing the thickness of the nonmagnetic metal film. The non-magnetic film for the purpose of separating magnetic interaction between the constituent blocks may have the same composition as the above-mentioned non-magnetic metal film. Therefore, the film thickness does not need to be near 2 nm. .

(Reference Example) Ni ₈₀ Fe ₁₀ Co ₁₀ (magnetic film) and Cu (non-magnetic metal film) were used as targets (all compositions were atomic%), and the thickness of the NiFeCo layer was 3 nm.
An artificial lattice film having a Cu layer thickness of 2 nm and a lamination number of 10 was formed such that sputtered atoms were obliquely incident on the substrate. This membrane has a K of about ⁴ × 10 ⁴ / cc and a J of about −2 × 10 ⁴ erg / cc;
The condition K> | J | of the present invention is satisfied. When the MR curve of the film thus obtained was measured by applying a magnetic field in the easy axis direction, the result shown in FIG. 1 was obtained. After forming the artificial lattice magnetoresistance change portion in this manner, an SiO ₂ insulating film is formed thereon, and further, Au for the conductor wire is used.
Cr was deposited to produce a memory element.

In order to confirm the operation of this memory element, as shown in FIG. 3A, a + or-pulse current is applied to the conductor wire 1 to generate a magnetic field exceeding Hs or -Hs in FIG. The information is recorded by magnetizing the lattice film portion 2 in one direction, and then a weak pulse current that changes from + to-is applied to the conductor line 1 as shown in FIGS. A pulse weak magnetic field having an intensity of Hm was generated, and the resistance change of the artificial lattice magnetoresistive element at that time was measured as shown in FIG. 4 (d). The result was recorded as shown in FIG. 4 (d). The memory function was confirmed from the fact that the resistance change clearly changed to + (increase) or-(decrease) depending on the magnetization direction.

(Example) Ni ₈₀ Fe ₁₀ Co ₁₀ (soft magnetic film) was used as a target in the same manner as in the reference example .
Using Cu (non-magnetic metal film) (all compositions are atomic%), NiF
An artificial lattice film having an eCo layer thickness of 3 nm, a Cu layer thickness of 2 nm, and a lamination number of 10 was formed such that sputtered atoms were obliquely incident on the substrate. After producing the artificial lattice magnetoresistance change portion in this way, an SiO ₂ film insulating film was formed thereon, and AuCr for a conductor wire was further formed to produce an amplification element.

In order to confirm the operation of this amplifying element, FIG.
As shown in FIG.
A magnetic field exceeding Hs is generated, the magnetization direction of the artificial lattice film portion is initialized, and then an input AC voltage is applied to the conductor wire 1 to flow a weak current as shown in FIG. Of the artificial lattice magneto-resistive element portion 2 was measured so that the output voltage change due to the resistance change of the conductor portion was measured. As shown in FIG. The element was confirmed to have an amplification function by amplifying the input voltage as described above.

[0023]

According to the present invention, as a device using the magnetoresistive effect with a simple structure, a small memory device and an amplifying device capable of operating at a low current can be realized.

[Brief description of the drawings]

FIG. 1 shows MR of an artificial lattice magnetoresistive element of the present invention.
Diagram showing an example of a (magnetic resistance) curve

FIG. 2 is a configuration diagram of a memory element and an amplification element of the present invention.

FIG. 3 is a diagram illustrating the operation of the memory element of the present invention.

FIG. 4 is an explanatory diagram of the operation of the amplifying element of the present invention.

FIG. 5 is a configuration diagram of a conventional memory element utilizing a magnetoresistance effect.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductor wire 2 artificial lattice film 2 M magnetic metal film 2 N non-magnetic metal film 3 insulating film S information reading unit composed of artificial lattice magnetoresistive film M information holding unit composed of hard magnetic film R, R ′ magnetic field applying current line

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Kawabata 1006 Oaza Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-6-243673 (JP, A) JP-A-4 -302103 (JP, A) JP-A-8-55313 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 43/08 G11C 11/14 H01F 10/08 JICST file (JOIS )

Claims (7)

(57) [Claims] 1. An anti-ferromagnetic coupling through a non-magnetic metal film
[Magnetic metal film / Nonmagnetic gold]
Metal film / magnetic metal film] an artificial lattice film conductor portion and the vicinity of this conductor portion
A metal conductor wire provided on the side with an insulating film interposed is provided.
The exchange coupling energy between the permeable membranes is J (<0),
When the magnetic anisotropy energy of the film is K, the artificial lattice
The film part satisfies K> | J |, and current is applied to the metal conductor wire.
The direction of the magnetic field generated by flowing and the K of the artificial lattice film
So that the directions of the easy axes of magnetization are almost parallel.
And the MR curve of the artificial lattice film portion (resistance change curve due to the magnetic field)
Line) indicates that the generated magnetic field H is increased from 0 to H> 0.
In the case, the resistance of the artificial lattice film part once increased and showed a maximum.
After that, the resistance value decreases and becomes almost the same resistance value as in the case of H = 0.
After that, when H is decreased, there is almost no resistance change until H = 0.
When the magnetic field is reversed and the magnetic field is increased in the H <0 direction,
The resistance increases once, decreases after showing the maximum, and when H = 0.
Amplification characterized by operating with almost the same resistance value
element. 2. The method according to claim 1, wherein the artificial lattice film portion is a magnetic metal film / non-magnetic film.
Metal film] as a component, and at least this component
2. The method according to claim 1, wherein the layers are laminated three or more times.
Amplifying element. 3. The method according to claim 1, wherein the magnetic metal film of the artificial lattice film portion is NixC.
X is a magnetic film containing oyFez as a main component.
0.6-0.9, Y is 0-0.4, Z is 0-0.3
3. The amplifying device according to claim 1, wherein: 4. The method according to claim 1, wherein the magnetic metal film of the artificial lattice film portion is Nix '.
Main component is Coy'Fez ', and X' is 0 to 0 in atomic composition ratio.
0.4, Y 'is 0.2-0.95, Z' is 0-0.5
3. The amplifying element according to claim 1, wherein the amplifying element is provided. 5. The method according to claim 1, wherein the nonmagnetic metal film of the artificial lattice film portion is made of Cu,
2. The method according to claim 1, wherein the material is one of Ag and Au.
5. The amplifying element according to any one of items 1 to 4. 6. The non-magnetic metal film of the artificial lattice film portion is made of Cu.
The method according to any one of claims 1 to 4, wherein
Amplifying element. 7. A non-magnetic metal film having a thickness of 1.5 nm or less.
The thickness is not more than 2.5 nm.
7. The amplifying element according to any one of 6.