JPH0283889A - Magnetic storing element and its driving method - Google Patents

Abstract

PURPOSE:To stably hold a Bloch line pair on a magnetic wall by arranging the column of a conductor to form a closed circuit approximate to a ferromagnetic body film where a stripe domain exists as a means to hold the Bloch line pair. CONSTITUTION:A soft magnetic stripe domain (SD) 4 in a ferromagnetic body film 7 is held so that a groove 3, in which the film surface is groove-dug over the same depth as the film thickness, can be included in the internal part. Infor mation is stored as the presence and absence of a Bloch line (BL) pair 6 on an SD magnetic wall 5. A closed circuit conductor 1 to stabilize the driving of a BL pair and hold the stability is crossed perpendicular to the SD magnetic wall on a film surface and arranged mutually in parallel. A hard film thin line group which is a BL pair holding means is also crossed perpendicular to the SD magnetic wall at the same period on a closed circuit conductor col umn and arranged mutually in parallel. For the bias pulse magnetic field in a Z direction to drive the BL line pair, the non-symmetrical pulse magnetic field having a steep rise and a smooth fall is used.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a nonvolatile ultra-high density magnetic memory element.

(Problems to be Solved by the Prior Art and the Invention) Magnetic bubble elements are being actively developed in various places as a substitute for high-density solid-state magnetic storage elements. However, with the currently used garnet materials, the minimum attainable bubble diameter is 0.
It is said to be 3pm. Therefore, a bubble material that retains bubbles with a diameter of 0.3 pm or less must be found other than garnet material. This is not easy and is even considered to be the limit of bubble density. We have developed an ultra-high-density magnetic memory element that is magnetized in the direction perpendicular to the film surface, which can significantly improve the high-density limit based on the characteristics of the bubble retention layer, and keep the information readout time at the same level as conventional elements. A Bloch line consisting of two pairs of perpendicular Bloch lines that statically and stably exist within a Bloch domain wall that forms the boundary of a stripe domain formed in a soft magnetic ferromagnetic (including ferrimagnetic) film with an easy direction. An element using a pair (hereinafter referred to as a VBL pair) as a storage unit was invented (Japanese Patent Application No. 182346/1982).

One of the most important parts of this device is the transfer of the VBL pair that carries information.

In principle, for selective transfer of one bit at a time, a means is required to apply a force to drive the VBL pair along the domain wall. In reality, a method of applying a local in-plane magnetic field in the form of a traveling wave along the domain wall surface to the VBL pair existence region, and a method of applying a pulse bias magnetic field to the stripe domain domain wall to dynamically move the domain wall and thereby causing the VBL pair to change. It has been considered to utilize gyroscopic force, which is a type of reaction that occurs due to position, but the former is only achieved by using conductor patterns, so it is not practical when aiming to increase the density of elements. . On the other hand, in the latter case, the domain wall driving force provided by the externally applied pulsed bias magnetic field is very important. In order to make this domain wall driving force constant in each part of the chip, it is important to stabilize the Bloch line pairs on the striped domain domain wall, that is, to stably hold the Bloch line pairs on the striped domain domain wall. Become. The technology for this method will be explained in detail.

Conventionally, as a method to maintain the Bloch line pair stably,
For example, a group of fine wires made of a hard magnetic film are arranged in-plane and perpendicular to the stripe domain domain wall via an insulating layer on the stripe domain domain wall transfer path, and the magnetization of the group of thin wires is magnetized in the direction of the stripe domain domain wall. There are known methods to
Ranzak John, Ob, Magnetics, MAG-2
2, pp. 784-789, September 1986). Other methods such as stress and ion implantation have also been proposed.

All of these methods involve arranging a group of thin wires having stripes on the soft magnetic ferromagnetic material film in which the striped domains are present in order to maintain Bloch line pairs, or arranging a thin line mask to maintain the soft magnetic ferromagnetic material. This is achieved by selectively modulating the film characteristics of the film surface layer spatially by implanting ions from above the magnetic film. Even in the already known effective method of arranging the hard film thin wire group on a soft magnetic film, the magnetic charge caused by the magnetization of the end of the hard film mainly causes the soft magnetic ferromagnetic film to It has a structure that can apply a spatially modulated magnetic field to the surface layer.

On the other hand, as a means for driving Bloch line pairs, a method using a spatially uniform and temporally modulated pulsed bias magnetic field has been proposed as a means applicable to large-capacity storage elements.

In this way, the conventional Bloch line pair holding means described above is a Bloch line pair driving means.
These are mutually independent means that have no correlation with the driving of the Bloch line pair by a spatially uniform and temporally modulated pulsed bias magnetic field. That is, the conventional Bloch line pair driving and holding means are temporally different from each other.
Furthermore, it is composed of two independent means that have no spatial correlation.

However, in order to achieve stable Bloch line pair driving and holding, it is not enough to simply provide a Bloch line pair holding mechanism that is uncorrelated with the bias pulse magnetic field that is the driving means. It is necessary to have the function of promoting the Bloch line pair at the human position and stably holding the Bloch line pair at the human position. Moreover,
In order to apply it to a large-capacity element, it is necessary to realize such a function without consuming extra power.

An object of the present invention is to eliminate such conventional problems and to provide an ultra-high density magnetic memory element having means for stably holding the Bloch line pairs on the stripe domain domain wall.

(Means for Solving the Problems) That is, the present invention has information reading means, information writing means, and information storage means, and uses a ferromagnetic material (phenomagnetic material) whose easy magnetization direction is perpendicular to the film surface. A vertical Bloch line pair consisting of two adjacent vertical Bloch lines created in a Bloch domain wall at the boundary of a strive domain in a film (including a body) is used as a storage information unit, and a bias pulse is applied to the vertical protubo line pair. In a magnetic memory element equipped with a means for transferring data within a Bloch domain wall using a magnetic field, the rise time and fall time of the striped tome magnetic field are determined in close proximity to the ferromagnetic film of the soft magnetic material in which the striped domains are present. This is a driving method characterized by applying a first pulsed magnetic field both having a length of Ion seconds or more and a second pulsed magnetic field having either a rise time or a fall time of 0.1 ns or less.

(Embodiment) The present invention provides a magnetic memory element having stable Bloch line pair driving and holding means by adopting the above-described configuration. Hereinafter, a detailed explanation of a configuration example of the present invention will be given.

FIGS. 1(a) and 1(1)) show an example of the configuration of an element including a closed circuit conductor for stably driving and holding a Bloch line pair in the present invention.

In FIG. 1, a stripe domain 4 in a soft magnetic ferromagnetic film 7 is held so as to include therein a groove 3 which is formed by digging the film surface to a depth equal to the thickness of the film.

The effect of the present invention will not change in the slightest even if the live domain holding means is formed by digging a groove as in this embodiment, or by other means such as a hard film. The information is stored as the presence or absence of the Bloch line sentence 46 on the live domain domain wall 5. Closed circuit conductors 1 for stabilizing and stably maintaining the driving of the Bloch line pair are arranged on the film surface so as to intersect perpendicularly to the stripe domain domain walls and to be parallel to each other. A group of hard film fine wires, which are Bloch line pair holding means, are also arranged on the closed circuit conductor row so as to intersect perpendicularly to the striped domain domain wall at the same period and to be parallel to each other (not shown).

The bias pulse magnetic field in two directions for driving the Bloch line pair is an asymmetric pulse-shaped pulse magnetic field in which the pulse rises steeply and the pulse falls gradually, as shown in FIG. Alternatively, a pulsed magnetic field with a gradual rise and a steep fall will produce essentially the same driving force.

This bias pulse magnetic field is applied as a substantially uniform magnetic field in a direction perpendicular to the film surface of the element. If the rise time or fall time of such a bias pulse magnetic field is too steep, the striped domain domain walls cannot move following the pulse time, and therefore, the pronovo line is difficult to move. Therefore, normally the steepest of the rising and falling times is 50 seconds to 1 seconds.
The slow speed ranges from about 100 ns to lpm.

However, as in the present invention, a row of conductors forming a closed circuit is provided in contact with a ferromagnetic film, and a first bias pulse magnetic field having a rise time and a fall time of both Ion seconds or more for Bloch line pair driving is applied. In addition, when a second bias pulse magnetic field with a steep rise time or fall time of 0.1 ns or less is applied, the time change in the magnetic flux interlinking with the closed circuit is the same as that of the first pulse. There is only a small contribution from the magnetic field, but a large contribution from the second pulsed magnetic field, and an electromotive force proportional to the time change in magnetic flux due to the second pulsed magnetic field is generated in the closed circuit, creating a closed circuit conductor with finite resistance. A current flows through.

In the case of this embodiment, the first bias pulse magnetic field has a peak value of 50e, a rise time of 50 ns and a fall time of 900 ns as shown in FIG. 3, and the second bias pulse magnetic field has a peak value of 50 e as shown in FIG. Peak value 0.50e, rise 0.
A driving pulse with a pulse waveform of 1 ns and a fall of 100 ns is applied. The directions of the twelfth and second pulsed magnetic fields are applied in the same direction. Each one of the closed circuit conductor rows is made of gold and has a rectangular shape as shown in FIG.
The conductor thickness is 1 pm, the conductor width is 1 pm, the distance between conductors facing perpendicular to the striped domain domain wall is 120 pm, and the distance between conductors facing in the direction parallel to the striped domain domain wall is 21
It is 1m. This rectangular closed circuit conductor is formed on a soft magnetic ferromagnetic film with an insulating layer of 5i02 having a thickness of 0.05 pm interposed therebetween. Rising time: 50 ns, falling time: 900 ns
Although the Bloch line pair receives a driving force and transfers due to the first pulse of n seconds, the dielectric current generated in the closed groove body is very small. On the other hand, at the rise of the second pulse with a rise time of 0.1 ns and a fall time of 100 ns, the magnitude of the magnetic flux change interlinking the closed circuit is ~1.2 x 1
O-3Wb1 second, and the resistance of the closed circuit where electromotive force is generated due to electromagnetic induction effect is ~6Ω, so ~0.2
A current of mA is generated at the rising edge of the pulse. When the second pulse amplitude reaches its maximum value and when it falls, the electromotive force generated in the closed circuit is less than 1/100 of the rise, and during this period, the current generated in the closed circuit is less than that at the rise. , can be regarded as almost 0. Since the rise time of the second pulsed magnetic field is steep and as small as 0.50e, it does not serve as a driving force for the Bloch line pair.

That is, only when the second bias pulse magnetic field rises,
A current flows through the closed circuit string, and the current generates a magnetic field under the closed circuit conductor in a direction opposite to the first bias pulse magnetic field. Since the closed circuit is provided close to the ferromagnetic film, the magnetic field caused by the current induced in the closed circuit by the second pulsed magnetic field becomes a relatively large magnetic field in the ferromagnetic film. In this way, if the delay time between the first pulse magnetic field and the second pulse is fixed, the magnetic field generated by the closed circuit will maintain a constant delay time with respect to the first bias pulse magnetic field. and is spatially synchronized with the arrangement period of the closed circuit. Therefore, when the bias pulse magnetic field pulse rises, the soft magnetic ferromagnetic film under the closed circuit conductor is superimposed with the opposite magnetic field from the closed circuit conductor.
The bias pulse magnetic field is effectively weakened. On the other hand, outside the closed circuit conductor, the magnetic field from the circuit conductor is in the same direction as the bias pulse magnetic field, so the bias pulse magnetic field is effectively strengthened.

Therefore, as shown in FIG.
), when the bias pulse magnetic field 2 rises steeply, the Bloch line pair held at the bit position, which is the striped domain domain wall portion under the closed circuit conductor, begins to be driven by the steep rise of the bias pulse; Moreover, the magnetic field from the closed circuit conductor has the effect of being drawn out of the closed circuit conductor from the original bit position. That is,
The driving force to the adjacent closed circuit conductor at the next bit position is strengthened. After the Bloch line pair has been driven to the adjacent bit position, when the bias pulse magnetic field pulse gradually falls, the force that drives the Bloch line pair in the opposite direction due to the bias pulse magnetic field is small, and the magnetic field of the closed circuit conductor is This is negligible, and there is no extra effect of causing a Bloch line pair that once reached an adjacent bit position to return to its original bit position, and remains stable at the adjacent bit position.

The closed circuit conductor strengthens the driving of the Bloch line pair to the adjacent bit position only when the bias pulse magnetic field rises steeply, whereas when the bias pulse magnetic field gradually falls after reaching the adjacent bit position, There is no effect that promotes the return of the Bloch line pair. Moreover, this closed circuit conductor effect is achieved without consuming any extra power.

As a second embodiment, when the first pulsed magnetic field and the second pulsed magnetic field are synchronized by increasing the delay time as shown in FIG. 4(b), and the magnetic field directions are reversed, the second pulsed magnetic field The magnetic field caused by the current induced in the closed circuit has the effect of suppressing the return of the Bloch line pair transferred to the adjacent bit.

(Effects of the Invention) As described above, in the magnetic memory element of the present invention, the conventional problem of driving and holding a Bloch line pair by a bias pulse magnetic field can be solved by arranging a closed circuit conductor, and a large capacity This is a dog that will contribute to the practical application of magnetic memory elements.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are diagrams showing the main parts of the present invention, FIG. 2 is a diagram showing the first pulse waveform for bias pulse driving, and FIG. 3 is a diagram showing the second pulse waveform. FIG. 4 is a diagram showing a pulse waveform, and FIGS. 4(a) and 4(b) are diagrams showing the magnitude, direction, and phase relationship of the first pulse and the second pulse of the present invention. 1 closed circuit conductor, 2 bias pulse magnetic field, 3 groove for holding stripe domains, 4 stripe domains, 5 stripe domain domain walls, 6 Bloch line pairs, 7 soft magnetic ferromagnetic film.

Claims (2)

[Claims] (1) A stripe existing in a soft magnetic ferromagnetic material (including ferrimagnetic material) film that has information reading means, information writing means, and information storage means and whose easy magnetization direction is perpendicular to the film surface. In a magnetic memory element having means for driving a vertical Bloch line pair consisting of two adjacent vertical Bloch lines formed in a Bloch domain wall at the boundary of a domain within the Bloch domain wall, the stripe is used as a means for holding the Bloch line pair. A magnetic memory characterized in that on the soft magnetic ferromagnetic film in which domains are present, a row of conductors forming a closed circuit is arranged close to the ferromagnetic film so as to intersect the striped domain domain wall. element. (2) As the first bias pulse magnetic field for driving the Bloch line pair, an asymmetric pulse magnetic field with both a rise time and a fall time of 10 ns or more and an asymmetric pulse magnetic field with either a rise time or a fall time of 0.1 ns or less 2
2. The method of driving a magnetic memory element according to claim 1, wherein a pulsed magnetic field of .