JPH01112587A - Driving method for magnetic storage element - Google Patents

Abstract

PURPOSE:To contrive to prevent the occurrence of a transfer error by applying >=2 same pulse-shaped bias magnetic fields to drive a VBL pair. CONSTITUTION:A magnetic wall 13 at the outside of a stripe magnetic domain 12 stabilized around a groove 11 dig into a garnet is used for a transfer path of the VBL pair, and a current is given to a zigzag conductor 21 to generate a local planer magnetic field thereby forming a stable position 5 of the VBL pair 1 on the magnetic wall 13, and plural pulse-shaped bias magnetic fields are applied externally to transfer the VBL pair 1 to the next position 5 without making the magnetic wall 13 unstable dynamically. Thus, the speed of the magnetic wall is suppressed to be less than a peak speed, and the dynamic change in the state of magnetic wall is suppressed thereby preventing the occurrence of a transfer error.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for driving a pair of vertical Bloch lines using a pulsed bias magnetic field used in a Bloch line memory.

(Prior art and its problems) Magnetic bubble memory elements are being actively developed in various places with the aim of becoming high-density solid-state magnetic memory elements. However, with currently used garnet materials, the minimum attainable bubble diameter is said to be 0.3 pm. Therefore, 0.
A bubble material other than garnet material that retains bubbles with a diameter of 3 pm or less must be found. This is not easy, and this is considered to be the limit of increasing bubble memory density.

As an ultra-high-density solid state magnetic memory element that greatly improves the density limit due to the characteristics of the bubble retention layer, we have developed a ferromagnetic (including ferrimagnetic) film whose easy magnetization direction is perpendicular to the film surface. A Bloch line memory element was invented that uses a Bloch line pair (hereinafter referred to as a VBL pair) consisting of two vertical Bloch lines stably existing in a Bloch domain wall that forms the boundary of a striped magnetic domain to be formed as a storage unit. (Patent application No. 57-182346).

In a Bloch line memory element, information is written in the form of VBL pairs along the Bloch domain wall around the stabilized stripe magnetic domains that constitute the minor loop, and the information is written in the form of VBL pairs.
A means for reading information units represented by a minute area called L pairs, and a means for transferring and holding VBL pairs bit by bit on a minor loop are essential.

The stripe fixing method by trenching is used to stabilize the striped magnetic domain, and the local in-plane magnetic field generated from the battened in-plane magnetized film or current conductor is used to fix the bits of the VBL pair on the stabilized stripe. It is common to use the potential of A specific example is shown in FIG.

In Figure 3, 11 is a groove dug into the garnet layer;
12 is a striped magnetic domain that constitutes a minor loop, 13
5 is the stable position of the VBL pair, 1 is the VBL pair, 21 is a zigzag conductor button for bit fixing, and 25 is a bit fixing current. The striped magnetic domain 12 is stabilized around the groove 11, and the domain wall 13 outside of the striped magnetic domain 12 becomes a transfer path for the VBL pair.

When a current 25 is passed through the zigzag conductor button 21, a local in-plane magnetic field is generated, and the stable position 5 of the VBL pair is generated every other conductor.
is formed. The interval between the stable positions 5 of the VBL pair is determined by the processing accuracy of the zigzag conductor button 21, and in the case of Fig. 3, lp
The m-bang and lpm gap are still 4pm.

Transfer of VBL pairs is performed by applying a pulse-like bias magnetic field to the striped magnetic domains to move the domain walls in the normal direction of the striped magnetic domains, and using the resulting gyroscopic force to cause the VBL pairs to slide laterally within the domain walls. . However, in the case of a rectangular-wave bias magnetic field pulse, when the stripe magnetic domain returns to its original state at the fall of the pulse, the VBL pair moves in opposite directions, and the total amount of movement becomes almost zero. Therefore, as shown in Figure 4, the fall time of the bias magnetic field pulse is lengthened, and V
The unidirectional movement of the VBL pair is ensured by suppressing the return of the BL pair. The moving distance of the VBL pair depends on the magnitude and rise time of the pulsed bias magnetic field.

(Problem to be Solved by the Invention) However, in order to transfer the VBL pair from one bit position to the next bit position with one bias magnetic field pulse, a very large bias magnetic field pulse must be applied. , the domain wall becomes dynamically unstable, causing transfer errors.

An object of the present invention is to provide a method for driving a magnetic memory element that solves this problem.

(Means for Solving the Problems) The gist of the present invention is to provide a ferromagnetic (including ferrimagnetic) film whose easy magnetization direction is perpendicular to the film surface.
A pulsed bias magnetic field is applied in the direction perpendicular to the film surface,
In the method for driving a magnetic memory element in which a VBL pair consisting of two adjacent vertical Bloch lines formed in a Bloch domain wall at the boundary of a stripe domain existing in the ferromagnetic material is transferred and held as a storage carrier, two or more The idea is to apply the same pulsed bias magnetic field to drive the VBL pair.

(Function) Transfer errors in VBL pairs occur in a large pulsed bias magnetic field because, when the striped magnetic domain moves, the domain wall exceeds the peak speed of domain wall movement and a horizontal Bloch line is generated and punch-through occurs in the large driving magnetic field. is added in a short period of time.

By dividing the bias magnetic field pulse into a plurality of pulses, the velocity of the domain wall can be suppressed below the peak velocity, and dynamic changes in the state of the domain wall can be suppressed.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a pulse waveform diagram showing an embodiment of the present invention.

In the figure, 31 represents a pulse, and 32 represents a clock. To explain the present invention using FIGS. 1 and 3, a striped magnetic domain 1 stabilized around a groove 11 dug in garnet.
The outer domain wall 13 of 2 is used as a transfer path for the VBL pair, and a current is passed through the zigzag conductor 21 to generate a local in-plane magnetic field to form a stable position 5 of the VBL pair on the domain wall 13.
By applying a plurality of pulsed bias magnetic fields 31 shown in FIG. 1 from the outside, VB can be applied without making the domain wall 13 dynamically unstable.
This is to transfer the L pair to the next stable position 5.

FIG. 2 is a diagram showing the effect of the above embodiment, and shows the pulsed bias drive magnetic field margin characteristics of a device using a 5 pm bubble material. In the figure, the vertical axis represents a static bias magnetic field, and the horizontal axis represents a pulsed bias drive magnetic field. 2pm
A current of 1 mA was passed through a zigzag conductor batten with a width of lpm gap to form a stable position of a VBL pair with a period of 6 pm. Six pulsed bias drive magnetic fields having a rise time of 100 ns, a pulse width of 200 ns, and a fall time of 900 ns were applied continuously within one clock, and the margin shown in FIG. 1 was obtained.

Under the same conditions, if the number of pulsed bias drive magnetic fields was reduced to three or less, the transfer margin for the VBL pair could not be obtained. On the other hand, when the number of pulsed bias drive magnetic fields was increased to nine or more, two bits were transferred and an error occurred.

(Effects of the Invention) As described above, the present invention prevents the domain wall state from dynamically changing when the VBL pair is driven by a large pulsed bias magnetic field, and prevents the domain wall state from changing dynamically below the peak speed of domain wall movement. A large operating margin can be obtained by driving the VBL pair in small intervals.

In addition, in this example, VB due to the current flowing through the zigzag conductor
Although the L-pair stabilization method was used, it is clear that similar effects can be obtained even when a battened in-plane magnetization film or the like is used.

[Brief explanation of the drawing]

FIG. 1 is a pulse waveform diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing measurement results of pulsed bias magnetic field margin characteristics of VBL versus transfer, and FIG. 3 is a diagram showing striped magnetic domains and VB
FIG. 4 is a batan diagram showing an example of a method for stabilizing the L pair, and FIG. 4 is a pulse waveform diagram showing a conventional method for driving a magnetic memory element. In the figure, 1 is a pair of vertical Bloch lines, 5 is a stable position of a pair of vertical Bloch lines, 11 is a groove dug into garnet, 12 is a striped magnetic domain, 13 is a domain wall, 21 is a zigzag conductor button, and 25 is a bit fixing hole. 31 is a bias magnetic field pulse, and 32 is a clock.

Claims (1)

[Claims] A pulsed bias magnetic field is applied in the direction perpendicular to the film surface to a ferromagnetic material (including ferrimagnetic material) film whose easy magnetization direction is perpendicular to the film surface, and the striped domains existing in the ferromagnetic material are In a method for driving a magnetic memory element in which a vertical Bloch line pair consisting of two adjacent vertical Bloch lines formed in a Bloch domain wall at a boundary is transferred and held as a memory carrier, the pulsed bias magnetic field is A method for driving a magnetic memory element, characterized in that the pulsed bias magnetic field is: