JPS6160504B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in bubble domain generators patterned with thin film metal on magnetic bubble memory chips.

In general, magnetic thin films have an easy axis of magnetic domain in the in-plane direction, but certain magnetic materials, such as single crystals such as orthoferrite and magnetic garnet, have a strong uniaxial anisotropy that has an easy axis of magnetization only in the C-axis direction. It has directionality. When such a material is made into a thin film with a surface perpendicular to the C-axis, when no external magnetic field is applied, the upward magnetization direction magnetic domain 1 and the downward magnetization direction magnetic domain 2 have approximately equal areas, as shown in Figure 1a. They are intertwined in a striped pattern. When a downward bias magnetic field H _B is applied to this thin film, the upward magnetic domain 1 decreases, the downward magnetic domain 2 expands, and the first
After passing through the state shown in Figure b, the upwardly directed magnetic domain becomes a small cylinder with a diameter of several μm, as shown in Figure 1C. This cylindrical magnetic domain 3 is called a magnetic bubble domain. The magnetic bubble memory device utilizes the fact that the magnetic bubble domains can move freely within a magnetic thin film by a magnetic field.
Alternatively, a propagation path is formed by forming a matrix of patterns such as half disks as shown in FIG. 2b,
Information is stored by transferring magnetic bubbles and setting "1" where there is a magnetic bubble and "0" where there is no magnetic bubble. Therefore, magnetic bubbles must be generated according to the information to be stored. Moreover, when the bias magnetic field is further strengthened from the state shown in FIG. 1c, the magnetic bubble domain suddenly collapses and disappears from a certain radius. To create a new magnetic bubble domain from this state, it is necessary to locally apply a pulsed magnetic field of several thousand Oe in the opposite direction to the bias magnetic field. This magnetic field is called a nucleation magnetic field (H _N ). FIG. 3 shows a nucleation-type bubble magnetic domain generator using this method, which combines a hairpin-shaped conductor 4 for generating a local magnetic field and a pickaxe-shaped permalloy pattern 5. This bubble magnetic domain generator generates bubbles 6 by passing a pulsed current through the conductor pattern 4 to generate a magnetic field in the opposite direction to the bias magnetic field. However, when bubbles are generated using this nucleation type bubble magnetic domain generator, as the temperature rises, the nucleation magnetic field (H _N ) of the magnetic thin film decreases, so that the bubbles become larger. For this reason, when propagated to the propagation path by the rotating magnetic field, the bubbles cannot contract suddenly, and as shown in Figure 4, the bubbles stretch and become easy to break, causing one bubble to become two or more, causing malfunction. It may become. The present invention has been devised to remedy this drawback.

Therefore, in the bubble magnetic domain generator of the present invention, a hairpin-shaped conductor pattern, a side that is arranged along the parallel part of the conductor pattern and has a length equal to or longer than the length of the bubble generated in the hairpin part of the conductor; and a permalloy pattern having a side connected to the side to propagate the bubble and propagate the bubble to another propagation pattern.

Embodiments of the present invention will be described in detail below based on the accompanying drawings.

FIG. 5 shows a plan view of the embodiment. In the figure, numeral 7 is a hairpin-shaped conductor pattern, and 8 is a substantially L-shaped permalloy pattern. One side 8a of this permalloy pattern 8 is arranged along the parallel portion of the hairpin-shaped conductor 7 so as to be overlapped, and its length is longer than the length of the bubble generated in the hairpin loop of the conductor 8. The other side 8b of the permalloy pattern 8 extends in the direction of the propagation patterns 9 and 9' so that bubbles can be transferred.

Note that 1 of the length of one side 8a of the permalloy pattern 8 arranged along the parallel part of the hairpin-shaped conductor 7
For example, (YSmLuCa) ₃ (GeFe) ₅ O ₁₂
In a 3 μm bubble device using a crystal of
_P (Peak Velocity) is 40m/sec and 300nsec
(pulse width of new creation current) is 12
~15 μm. Therefore, the length of one side 8a of the permalloy pattern 8 is approximately this.

In this embodiment formed in this manner, as shown in FIG. 6, when a pulse current flows through the hairpin-shaped conductor 7, a bubble 10 is generated along one side 8a of the permalloy pattern 8 as shown in the figure. After the pulse current is cut off, this bubble 10 is guided by the driving magnetic field to the other side 8b of the permalloy pattern 8 as indicated by the arrow P, but since it is not necessary to shrink rapidly, it is divided into two or more pieces. Nothing happens. Therefore, the upper limit of the pulse current value at high temperatures can be significantly increased, and the guaranteed operation range can be widened.

FIG. 7 shows a comparison of the generator current temperature characteristics of the product of the present invention and the conventional product. In the figure, the vertical axis represents the generator current and the horizontal axis represents the chip temperature.The solid line A shows the upper and lower limits of the characteristics of the product of the present invention, and the dotted line B represents the upper and lower limits of the characteristics of the conventional product. The hatched area A' indicates the guaranteed operation range of the product of the present invention, and the hatched area B' indicates the guaranteed operation range of the conventional product. From the figure, it can be seen that the product of the present invention has a larger current margin, especially on the high temperature side, than the conventional product, and the guaranteed operation range is expanded.

As explained above, the bubble magnetic domain generator according to the present invention makes it possible to increase the current margin, especially on the high temperature side, by forming a permalloy pattern having sides along the hairpin parallel portions of the hairpin-shaped conductor. This also contributes to improving the reliability of the magnetic bubble memory device.

[Brief explanation of the drawing]

Fig. 1 is a diagram of the principle of magnetic bubble generation, Fig. 2 is a plan view of the magnetic bubble propagation pattern, Fig. 3 is a plan view of a conventional bubble magnetic domain generator, Fig. 4 is an explanatory diagram of its operation, and Fig. 5 is a plan view of the magnetic bubble propagation pattern. FIG. 6 is a plan view of a bubble domain generator according to an embodiment of the present invention, FIG. 6 is an explanatory diagram of its operation, and FIG. 7 is a diagram showing the temperature characteristics of the generator current. 7... Hairpin-shaped conductor pattern, 8... Permalloy pattern, 9,9'... Propagation pattern, 10... Bubble.

Claims (1)

[Claims] 1 A hairpin-shaped conductor pattern, a side arranged along the parallel part of the conductor pattern and having a length equal to or longer than the length of a bubble generated in the hairpin part of the conductor, and a side connected to the side to propagate the bubble. and a permalloy pattern having edges that transfer the bubble to another propagation pattern.