Static information storage and retrieval – Systems using particular element – Magnetoresistive
Reexamination Certificate
2002-08-29
2004-04-13
Lebentritt, Michael S. (Department: 2818)
Static information storage and retrieval
Systems using particular element
Magnetoresistive
C365S171000, C365S173000, C257S421000, C428S692100, C428S682000
Reexamination Certificate
active
06721201
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetoresistive film using a perpendicular magnetic anisotropy film that can reverse its magnetization by a relatively small applied magnetic field and shows a relatively large magnetoresistive effect, and to a memory using the magnetoresistive film.
2. Related Background Art
The basic structure of a magnetoresistive film is a sandwiched structure formed by putting a non-magnetic layer between magnetic layers adjoining to each other. Cu and Al
2
O
3
can be cited as materials used as the non-magnetic layer frequently. A magnetoresistive film using a conductor such as Cu as its non-magnetic layer is called as a giant magnetoresistive film (GMR film). And, a magnetoresistive film using an insulator such as Al2O3 is called as a spin dependent tunneling magnetoresistive film (TMR film). Generally, a TMR film shows a larger magnetoresistive effect than that of a GMR film. Various applications of such a magnetoresistive film can be considered.
A memory using the magnetoresistive effect (MRAM) has recently been considered to be promising particularly among them. The MRAM is promising as a memory satisfying all specifications required by many kinds of information equipment in the aspects of its recording time, its reading time, its recording density, its possible number of times of rewriting, its electric power consumption and the like. In particular, because a large readout signal can be obtained from an MRAM using the spin dependent tunneling magnetoresistance (TMR) effect, the MRAM is advantageous to the increase of a recording density or to high speed readout. The realizability of the MRAM has been verified by recent reports of researches.
If the magnetization directions of two magnetic layers
13
and
14
are parallel to each other as shown in
FIG. 11A
, the electric resistance of the magnetoresistive film is relatively small. If the magnetization directions of the two magnetic layers
13
and
14
are anti-parallel to each other as shown in
FIG. 11B
, the electric resistance of the magnetoresistive film is relatively large. Consequently, it is possible to read information from the magnetoresistive film by utilizing the above-mentioned property by using one of the magnetic layers
13
and
14
as a memory layer and the other of them as a detection layer. For example, a magnetic layer
13
located above a non-magnetic layer
12
is used as the memory layer; a magnetic layer
14
located under the non-magnetic layer
12
is used as the detection layer; the state in which the magnetization direction of the memory layer faces to the right is supposed to the state of record information “1”; and the state in which the magnetization direction of the memory layer faces to the left is supposed to the state of record information “0”. If the magnetization directions of both of the magnetic layers
13
and
14
face to the right as shown in
FIG. 12A
, the electric resistance of the magnetoresistive film is relatively small. If the magnetization direction of the detection layer faces to the right and the magnetization direction of the memory layer faces to the left as shown in
FIG. 12B
, the electric resistance of the magnetoresistive film is relatively large. Moreover, if the magnetization direction of the detection layer faces to the left and the magnetization direction of the memory layer faces to the right as shown in
FIG. 12C
, the electric resistance of the magnetoresistive film is relatively large. If the magnetization directions of both of the magnetic layers
13
and
14
face to the left as shown in
FIG. 12D
, the electric resistance of the magnetoresistive film is relatively small. That is, if the magnetization direction of the detection layer is fixed to face. to the right, the record information “0” is recorded in the memory layer when the electric resistance is large, and the record information “1” is recorded in the memory layer when the electric resistance is small. Or, if the magnetization direction of the detection layer is fixed to face to the left, the record information “1” is recorded in the memory layer when the electric resistance is large, and the record information “0” is recorded in the memory layer when the electric resistance is small.
If the device size of the MRAM is made to be smaller for increasing the recording density thereof, the problem is produced in which it becomes impossible for the MRAM using an in-plane magnetic film to hold information owing to the influences of a demagnetization field or the curling of magnetization on end faces. For escaping the problem, a measure such as forming the shapes of the magnetic layers to be a rectangle can be cited. However, the measure cannot make the size of the device smaller, and consequently it is difficult to expect the improvement of the recording density. Accordingly, the proposal of escaping the above-mentioned problem by the use of a perpendicular magnetic anisotropy film was submitted, for example, as the disclosure in U.S. Pat. No. 6,219,725. Because the demagnetizing field does not increase even if the device size becomes small in accordance with the method, the method makes it possible to realize a magnetoresistive film having a size smaller than that of the MRAM using the in-plane magnetic film.
Like the magnetoresistive film using the in-plane magnetic film, the electric resistance of the magnetoresistive film using the perpendicular magnetic anisotropy film is relatively small if the magnetization directions of two magnetic layers are parallel to each other, and the electric resistance becomes relatively large if the magnetization directions are anti-parallel to each other. In
FIGS. 13A
,
13
B,
13
C and
13
D, a magnetic layer
23
located above a non-magnetic layer
22
is used as a memory layer; a magnetic layer
21
located under the non-magnetic layer
22
is used as a detection layer; the state in which the magnetization direction of the memory layer faces upward is supposed to the state of the record information “1”; and the state in which the magnetization direction of the memory layer faces downward is supposed to the state of the record information “0”. If the magnetization directions of both of the magnetic layers
23
and
21
face upward as shown in
FIG. 13A
, the electric resistance of the magnetoresistive film is relatively small. If the magnetization direction of the detection layer faces downward and the magnetization direction of the memory layer faces upwards as shown in
FIG. 13C
, the electric resistance of the magnetoresistive film is relatively large. Moreover, if the magnetization direction of the detection layer faces upward and the magnetization direction of the memory layer faces downward as shown in
FIG. 13B
, the electric resistance of the magnetoresistive film is relatively large. And, if the magnetization directions of both of the magnetic layers
23
and
21
face to downward as shown in
FIG. 13D
, the electric resistance of the magnetoresistive film is relatively small. That is, if the magnetization direction of the detection layer is fixed to face upward, the record information “0” is recorded in the memory layer when the electric resistance is large, and the record information “1” is recorded in the memory layer when the electric resistance is small. Or, if the magnetization direction of the detection layer is fixed to face downward, the record information “1” is recorded in the memory layer when the electric resistance is large, and the record information “0” is recorded in the memory layer when the electric resistance is small.
The following films can be cited chiefly as the perpendicular magnetic anisotropy film: an alloy film or an artificial lattice film which is composed of at least one kind of element selected among rare earth metals such as Gd, Dy and Tb and at least one kind of element selected among transition metals such as Co, Fe and Ni, an artificial lattice film made of a transition metal and a noble metal such as Co/Pt, and an alloy film having a magne
Lebentritt Michael S.
Nguyen Nam
LandOfFree
Magnetoresistive film and memory using the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetoresistive film and memory using the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetoresistive film and memory using the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3207341