JPH0227587A - Magnetic memory element driving method - Google Patents

Abstract

PURPOSE:To prevent a transferring error from being generated by providing a pulse pause period longer than the rise time of a pulselike bias magnetic field after the pulselike bias magnetic field. CONSTITUTION:A magnetic wall 13 on the external side of a stripe magnetic domain 12 stabilized around a groove 11 cut into a garnet is made into the transferring path of a pair of Bloch lines (VBL), a current is applied through a parallel conductor 21, a local magnetic field is generated, and a stable position 5 of the VBL pair is formed on the magnetic wall 13, a pulselike bias magnetic field 31 is externally impressed, and a VBL pair 1 are transferred to the next stable position 5. Thereafter, by the pulse pause period longer than the rise time of the pulselike bias magnetic field, the VBL pair 1 are stabilized at the root of a local intra-surface magnetic field potential by means of the parallel conductor. Thus, the dispersion of the pause position of the VBL pair driven by the pulselike bias magnetic field is eliminated, the start line of the VBL pair for the next driving is aligned, and the transferring error can be prevented.

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) As an ultra-high density solid-state magnetic memory element to replace magnetic bubble magnets and warped elements, boundaries between striped magnetic domains existing in a ferromagnetic (including ferrimagnetic) film whose easy magnetization direction is perpendicular to the film surface. A Bloch line pair consisting of two vertical Bloch lines (
A Bloch line memory element using VBL pairs (hereinafter referred to as VBL pairs) as a memory unit was invented (Japanese Patent Laid-Open No. 57-18
2346).

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 a minor loop, and the VBL
means for reading out information units represented by minute regions called pairs;
Also, a means for transferring and holding VBL pairs bit by bit on the minor loop is essential.

The stripe fixing method by trenching is used to stabilize striped magnetic domains, and the local in-plane fixation method generated from battened in-plane magnetized films and current conductors is used to fix bits of VBL pairs on the stabilized stripes. It is common to use the potential of a magnetic field. A specific example is shown in FIG.

In Figure 3, 11 is a trench dug into the Garne layer, 12
1 is a striped magnetic domain constituting a minor loop, 13 is a Bloch domain wall around the striped magnetic domain, 5 is a stable position of a VBL pair, 1 is a VBL pair, 21 is a parallel conductor pattern for bit fixing, and 25 is a bit fixing current. Stripe magnetic domain 1
2 is stabilized around the groove 11 and the outer domain wall 13 of 12
becomes the transfer path for the VBL pair.

When a current 25 is passed through the parallel conductor pattern 21, a local in-plane magnetic field is generated, and a stable position 5 of the VBL pair of each conductor is formed.

Transfer of the VBL pairs is performed by applying a pulsed bias magnetic field to the striped magnetic domains to move the domain walls in the normal direction of the striped magnetic domains, and by utilizing the accompanying gyroscopic force that causes 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, Figure 4 (
aXb), the falling time of the bias magnetic field pulse 31 is lengthened to suppress the return of the VBL pair and ensure unidirectionality of movement of the VBL pair. The moving distance of the VBL pair depends on the magnitude and rise time of the pulsed bias magnetic field. (FIG. 4(b) shows the clock 33.) (Problem to be solved by the invention) However, the bit fixed positions are spread out,
Individual VBLs that have moved relative to a fixed bit position
Pairs do not always stop at exactly the same position. Furthermore, VBL pair transfer errors may occur due to factors such as variations in memory element temperature and pulsed bias magnetic field conditions.

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 perpendicular Bloch lines formed in a Bloch domain wall at the boundary of a striped domain existing in the ferromagnetic material is transferred and held as a storage carrier, the pulsed bias The magnetic field is followed by a pulse pause period that is longer than the rise time of the pulsed bias magnetic field.

(Function) VBL pair transfer errors occur because the stopping position of the VBL pair driven by the bias magnetic field pulse varies due to factors such as variations in memory element temperature and pulsed bias magnetic field conditions, and this variation This is due to the fact that it is cumulative. By providing a pulse pause period that is longer than the rise time of the pulsed bias magnetic field after the bias magnetic field pulse, the VBL pair settles at the bottom of the potential of the local in-plane magnetic field for bit fixing, thereby eliminating variations in the stopping position of the VBL pair. I can do it.

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

FIG. 1 (aXb) is a pulse waveform diagram showing one embodiment of the present invention. To explain the present invention using FIGS. 1 and 3, the outer domain wall 13 of the striped magnetic domain 12 stabilized around the groove 11 dug in garnet is used as a transfer path for the VBL pair, and parallel conductors 21 to generate a local in-plane magnetic field to create a stable position 5 of the VBL pair on the domain wall 13.
is formed, and a pulsed bias magnetic field as shown in FIG. 1 is applied from the outside to transfer VBL pair 1 to the next stable position 5. Thereafter, the VBL pair 1 is stabilized at the bottom of the local in-plane magnetic field potential due to the parallel conductor by a pulse pause period that is longer than the rise time of the pulsed bias magnetic field. 33 is a clock.

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. 211
A current of 1 mA was passed through parallel conductor patterns with a width of m and a gap of 1 μm to form a stable position of a VBL pair with a period of 3 pm.

Size 60e, rise time 100ns, pulse flat part 2
After applying a pulsed bias drive magnetic field of 00 ns and fall time of 500 ns, a pulse pause period of 500 ns was provided to obtain the margin shown in FIG. The margin shown by the broken line in FIG. 2 is the margin when the pulse pause period is 50 nsl or not provided.

By providing a pulse pause period that is longer than the rise time of the pulsed bias magnetic field, the upper and lower limits of the margin were improved.

(Effects of the Invention) As described above, the present invention eliminates variations in the stop position of the VBL pair driven by a pulsed bias magnetic field, and eliminates transfer errors by aligning the start lines of the VBL pair for the next drive. A large operating margin can be obtained.

In this embodiment, a method of stabilizing the VBL pair using a current flowing through parallel conductors was used, but it is clear that the same effect can be obtained even when a battened in-plane magnetized film or the like is used.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are pulse waveform diagrams showing one embodiment of the present invention, Figure 2 is a diagram showing measurement results of pulsed bias magnetic field margin characteristics of VBL versus transfer, and Figure 3 is a diagram showing striped magnetic domains. FIGS. 4(a) and 4(b) are pulse waveform diagrams 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 parallel conductor button, and 25 is a bit fixing hole. current, 31 is a bias magnetic field pulse, 32 is a bias magnetic field pulse pause period, 3
3 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 Two adjacent blocks created in the Bloch domain wall at the boundary of
In a method for driving a magnetic memory element that transfers and holds a vertical Bloch line pair consisting of two vertical Bloch lines as a storage carrier, a pulse pause period longer than a rise time of the pulsed bias magnetic field is provided after the pulsed bias magnetic field. A method for driving a magnetic memory element characterized by: