JPS6076078A - Magnetic random access memory system - Google Patents

Abstract

PURPOSE:To increase the reading/writing speed with a random access and to simplify the constitution of a magnetic random access memory system with cost reduction, by energizing an address line to write information and detecting the direction of a magnetic domain by means of the magneto-resistance effect to read information respectively. CONSTITUTION:An external coil is used to give upward or downward magnetization to uniaxial magnetic anisotropic matters 1a serving as each memory unit. Then the selective energization is given between X-direction read/write lines X1, X2- and Y-direction read/write lines Y1, Y2-. The external coil is energized in the direction where the matters 1a- are magnetized upward while a ''Permalloy'' pattern 2 is kept under a heating state. Thus only the matter 1a of the heated part is easily magnetized upward. In the same way, the energization is given in the direction where the downward magnetization is carried out. Thus only the matter 1a at the heated part is easily magnetized downward. In such a way, the magnetizing directions of the matters 1a are set at random to set the magnetizing directions opposite to logics 1 and 0. Then the magnetizing direction is detected and read out to obtain a magnetic random access memory.

Description

[Detailed description of the invention] [Technical portion of the invention! I! F) The present invention relates to an Mt magnetic random access memory system that performs a memory function using the direction of magnetization of a uniaxial magnetic anisotropic material such as a bubble material.

[Prior art and its problems]

A memory device using magnetic bubbles has been put into practical use, but writing is transferred from the major line to each minor loop and transferred to each minor loop for storage, while reading is performed using the bubbles circulating in the minor loop. When the signal arrives at the gate position, 1 - 1 out is sent to the measurer line, and the signal is transferred to the detecting section via the measurer line and read. Therefore, compared to IC memory, the read/write speed is slow, and the bubble generator, gate, detector, etc. Jt requires complicated functional parts and is expensive.

(Objective of Origin 1) The object of the present invention is to solve such problems in memory devices using uniaxial magnetic anisotropy materials such as bubble materials, and to read and write data at high speed through random access. The object of the present invention is to realize a magnetic random access memory system that is simple in configuration and inexpensive.

[Structure of the invention]

The technical means according to the present invention taken to achieve this object are as follows: - Construct a large number of storage units with magnetic films having axial magnetic anisotropy, and provide a method for writing and reading information in each storage unit. Address lines are connected, and information is written by heating the storage unit by energizing the address line and applying a bias magnetic field, and reading information is performed using the bias magnetic field and the magnetic field created by the magnetic domains of each storage unit. A method is adopted in which the direction of the magnetic domains is detected in a superimposed state using the magnetoresistive effect.

[Embodiments of the invention]

Next, how the magnetic random access memory system according to the present invention is actually implemented will be explained using examples.

FIG. 1 is a perspective view of a memory device implementing a magnetic random access memory method according to the present invention. In this memory device, a large number of storage units 1a are formed in the shape of a grid on a substrate 1 such as GGG crystal used as a bubble material, and storage is performed in each storage unit.

On each storage unit 1a..., read/write lines X1, Xl... in the X direction and read/write lines Y1,
Y2... are connected via heat generating conductors.

FIG. 2 is an enlarged view of each storage unit 1a, in which (a) is a plan view and (b) is a cross-sectional view. Xl, x2
. . . are read/write lines in the X direction arranged at intervals in the X direction, and are made of a conductor. Yl,
Y2... are write lines in the Y direction arranged at intervals in the Y direction. read/write line x in each X direction,
, x2... and read/write lines in the Y direction Y1, Y2...
and are connected to each other by a heating conductor made of a permalloy pattern 2. And each pattern 2...
A storage unit 1a, which is made of a uniaxially magnetically anisotropic material formed on a GGG plate or the like, is formed below the memory unit 1a.

Magnetic materials with uniaxial magnetic anisotropy, such as bubble materials, require a small magnetic field to reverse magnetization at high temperatures. Therefore, in the present invention, an external coil is provided to magnetize the uniaxial magnetic anisotropic body 1a, which is each storage unit, in two directions or in a downward direction.

Then, while selectively energizing the X-direction read/write lines X1, Xl... and the Y-direction read/write lines Y1, Y2... to generate heat in the permalloy pattern 2, the -axis magnetic difference is applied to the external coil. Electricity is applied in the direction in which the rectangular bodies 1a... are magnetized upward. Then, only the uniaxial magnetic anisotropic body 1a of the heat generating part is easily magnetized upward. Similarly, X-direction read/write lines X 1 , X 2 . . . and Y-direction read/write lines Y1, Y
2... Selectively energize between the permalloy pattern 2
When a current is applied to the external coil in a direction in which the -axis magnetic anisotropic body 1a... is magnetized downward while generating heat, only the uniaxial magnetic anisotropic body 1a of the heat generating part is easily magnetized downward. do. In this way, the direction of magnetization of the -axial magnetic anisotropic body 1a is randomly set, and the direction of magnetization is set to logic "1".
A magnetic random access memory can be realized by making it correspond to "0" and detecting and reading the direction of magnetization. Note that by forming grooves 3 in each of the -axis magnetic anisotropic bodies 1a to partition the space between the respective -axis magnetic anisotropic bodies 1a, the -axis magnetic anisotropy of each The bodies 1a... are prevented from influencing each other thermally or magnetically.

In addition, permalloy pattern 2 and X-Y reading/writing line X,
, x2...Yl, Y2... and each -axis magnetic anisotropic body la... are insulated by an insulating layer 4 such as 5i02.

As described above, the bias magnetic field 11 is applied in a state in which the magnetic domains of each of the -axis magnetic anisotropic bodies 1a are magnetized upward or downward.
When b is applied, the magnetic field becomes stronger if the direction of magnetization of the magnetic domain is the same as the bias magnetic field, and becomes weaker if it is in the opposite direction. Therefore, between magnetic domains whose magnetization directions are opposite to each other,
Since the difference is twice the magnetic field of the magnetic domains, the direction of magnetization of the magnetic domains can be easily detected. To detect the direction of this magnetization,
A low current is passed between the read/write lines x1, x2, . . . in the X direction and the read/write lines yt, Y2, . Then, in the uniaxial magnetic anisotropic material "2" where the direction of magnetization of the magnetic domain is the same as the bias magnetic field, the resistance value of the permalloy pattern 2 increases due to the magnetoresistive effect, and the X-Y read/write lines x1, Xl... The current value between Yl, Y2, and so on decreases. On the other hand, on a uniaxial magnetic anisotropic unit in which the direction of magnetization of the magnetic domains is opposite to the bias magnetic field, the magnetic fields cancel each other out and become extremely small, so the resistance value of the permalloy pattern 2 due to the magnetoresistive effect is extremely small. the result,
X-Y reading and writing lines X1, X2... and Yi, y2.
...The current value between the two does not decrease.

In this way, the direction of magnetization of the magnetic domains of the -axis magnetic anisotropic bodies 1a... can be easily detected by using the magnetoresistive effect and the bias magnetic field, and the direction of magnetization of the magnetic domains of the -axis magnetic anisotropic bodies 1a... It is possible to read the storage state of .

[Effects of the Invention] As described above, according to the present invention, a large number of memory units are constructed of magnetic films having -axis magnetic anisotropy, and an address pattern for writing and reading information is provided in each memory unit. are connected. Information is written by heating the storage unit by supplying electricity to the address pattern and applying a bias magnetic field. For reading, a method is adopted in which the direction of magnetization of the magnetic domains is detected using the magnetoresistive effect in a state where the bias magnetic field and the magnetic field generated by the magnetic domains of each storage unit are superimposed. Therefore, information can be read and written at random, and even magnetic memory can be accessed at high speed. Furthermore, since reading is non-destructive, complicated control such as writing at the same time as reading is unnecessary. Furthermore, writing and reading can be performed using the same element, making the structure of the memory element simple and inexpensive.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a memory device implementing the magnetic random access method according to the present invention, and FIG. 2 is a plan view and a sectional view of each -axis magnetic anisotropic body. In the figure, 1 is a substrate of a memory device, 1a... is a uniaxial magnetic anisotropic material constituting a storage unit, 2 is a permalloy pattern, Xi, x2... are read/write lines in the X direction,
Yl, Yl, . . . indicate read/write lines in the Y direction, respectively. Patent Applicant: Fujitsu Limited Agent, Patent Attorney: Minoru Aoyagi Figure 1 Figure 2 (A)

Claims (1)

[Claims] A large number of memory units are constructed of magnetic films having uniaxial magnetic anisotropy, and address lines for writing and reading information are connected to each memory unit, and information is written by energizing the address lines. Information is read by heating the storage unit by heating the storage unit and applying a bias magnetic field, and with the bias magnetic field and the magnetic field generated by the magnetic domain of each storage unit superimposed, the orientation of the magnetic domain is detected using the magnetoresistive effect. Magnetic random magnetic
Access memory method.