JPS615506A - Generator for magnetic field - Google Patents

Abstract

PURPOSE:To increase intensity per unit currents of a magnetic field, to lower an applied current value required for the same generating magnetic field and to inhibit the heat dissipation of a coil by mounting a soft ferromagnetic material plate having a normal parallel with the central axis of the solenoid type coil to an end surface vertical to the central axis of the solenoid type coil. CONSTITUTION:A Helmholtz type coil in which coils such as solenoid type ones 1a, 1b are positioned oppositely through a clearance section 20 is used as a coil for generating a magnetic field. A sample piece 5 to which the magnetic field must be applied is positioned normally in the clearance section 20 in the coil in such a Helmholtz type magnetic-field generating coil. The magnetic field 21 generated is of a component in the direction along the central axis of the coil. Disks 2a, 2b consisting of a high permeability soft magnetic material are fitted brought into contact with end surfaces 10 vertical to the central axis of the solenoid type coil so as to each share holes together wit hollow sections 12 in the solenoid in such a case. Accordingly, magnetic field intensity generated per unit currents is increased, thus realizing a magnetic field generator having small power consumption in the coil section in the same magnetic field intensity.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a device that generates a magnetic field using a solenoid coil. More specifically, the present invention relates to a magnetic field generating device having a structure that makes it possible to strengthen the generated magnetic field.

(Prior art and its problems) A magnetoresistive bubble ILt'' that utilizes magnetic bubbles existing in a thin piece of magnetic material having i-uniaxial magnetic anisotropy perpendicular to the surface.
- For the purpose of stably holding the magnetic bubble number □ in the child, the □ bubble holding field perpendicular to the thin piece of magnetic material (
(hereinafter referred to as □bias magnetic field) is required. To generate a bias magnetic field, methods using permanent magnets and methods using solenoid-type hollow coils are well known.

In particular, when measuring and evaluating the magnetic properties of a magnetic bubble element, it is important to change the magnetic field.

Therefore, for the purpose of generating a bias magnetic field.

. Engineering□□1゜1. . It is common to use a waka85, wa, 271 id type coil.

On the other hand, in magnetic bubble devices, especially magnetic bubble memory devices that utilize magnetic bubbles as information carriers.

In order to increase the density of information, efforts have been made to miniaturize the diameter of the magnetic bubbles used. As magnetic bubbles become smaller, it is generally necessary to increase the saturation magnetization Ms of the magnetic material. As the saturation magnetization increases, the bias magnetic field that stably holds the magnetic bubble also increases accordingly. For example, when a magnetic garnet film is used as the magnetic material, when the magnetic bubble diameter is about 3 μm, the bias magnetic field is about 1500e;
The bias magnetic field that holds a 2 μm diameter magnetic bubble is approximately 2
For a diameter tc of 500e and 14m, approximately 3500e is required. Furthermore, a bias magnetic field of about 6000e is required to stably hold a magnetic bubble with a diameter of 0.5 μm.

As described above, a high bias magnetic field is required to evaluate a magnetic bubble device using minute magnetic bubbles. To generate a high bias magnetic field, it is sufficient to apply a large current to the magnetic field generating coil.

In a simple coil, the Ziehl heat generated in the coil is proportional to the square of the current value, so as the bias magnetic field increases, the temperature of the coil rises rapidly, making it impossible to stably evaluate and measure magnetic bubble elements. have.

(Purpose of the invention) The aim of the invention is to eliminate the above-mentioned drawbacks.

It is an object of the present invention to provide a magnetic field generating device which reduces the applied current value required for the same generated magnetic field and suppresses heat generation in the coil by increasing the strength per unit current of the magnetic field generated by a solenoid type magnetic field generating coil.

(Configuration of the Invention) The configuration of the magnetic field generating device according to the present invention includes at least one solenoid type magnetic field generation coil, and has a normal line parallel to the central axis on an end face perpendicular to the central axis of the solenoid type coil. It is characterized by the provision of a soft ferromagnetic flat plate.

(Detailed explanation of the configuration F!A) The present invention provides a magnetic field generating device having the above-described configuration.
1 (which solves the drawbacks of the prior art.

The principle of the present invention is to provide a flat plate of high magnetic permeability soft magnetic material on the outer end surface of the solenoidal magnetic field generating coil, and to increase the magnetic flux that would otherwise be widely dispersed in the outer part of the solenoidal magnetic field generating coil. The purpose is to emphasize the magnetic field inside the solenoid by absorbing the magnetic permeability into a magnetic flat plate and using the so-called mirror image effect.

(Example) Embodiments of the present invention will be explained below with reference to the drawings.

Example 1 A first example of the present invention will be described with reference to FIG. In this embodiment, as the AL field generating coil, a Shita Helmholtz type coil is used in which the solenoid type coils la and lb are placed opposite each other with a gap 20 interposed therebetween. Normally, in such a Helmholtz type magnetic field generating coil, the sample piece 5 to which the magnetic field is applied is
Place it in the gap 20 of the coil. The generated magnetic field 21 is a component in the direction along the central axis of the coil.

Discs 2a and 2b made of a soft magnetic material with high magnetic permeability are provided in contact with an end surface 10 perpendicular to the central axis of the solenoid-type coil so as to share their respective holes with the hollow portion 12 of the solenoid. If the solenoid coil has an inner diameter of 32 mm, an outer diameter of 95 mm, a thickness of 1511 mm, and a gap size of 16 mm, if a perforated circular plate of NiZn magnetic ferrite with a wall thickness of 3 mm is provided,
It has been found that a magnetic field that is approximately 20% stronger per unit current is generated than in the case without this.

In other words, to obtain the same generated magnetic field strength, a current value that is approximately 15 inches smaller is required, that is, the power consumption of this magnetic field generator is reduced by approximately 30%, and the generation of Joule heat is suppressed accordingly.

1m The second embodiment will be explained using FIG. use Flat plates 2a, 2 made of high magnetic permeability soft magnetic material
Unlike the previous example, b is simply a disk without a hole corresponding to the hollow part at the center of the coil. In this case, due to the lack of a hole in the central part.

In the previous example, leakage of the magnetic flux that was dispersed to the outside through the holes is avoided, and a more perfect mirror image of the coil is formed. Therefore, the generated magnetic field per unit current will further increase. In this example, we saw an increase of about 25 Ls - that is, to generate the same magnetic field, 20% less current is required, which reduces the power consumption of the coil. This is a decrease of about 35ts.

Example 3 A third example of the present invention will be described with reference to FIG. 3. In this example, the magnetic field generator shown in the first example is applied to a coil for evaluating magnetic bubble elements. There is. A coil 6 for generating a rotating magnetic field in one plane is provided in a gap 20 between the solenoid coils.

As the rotating magnetic field coil, a shape in which an excitation coil is wound around a magnetic ferrite ring, a Helmholtz type hollow coil, etc. are suitable for this purpose. The sample 5 is passed through a hollow part of a solenoid-type coil installed in the center of the coil gap and a corresponding perforated high-permeability disk 2a, and an optical system such as a microscope consisting of a light source 7 and an observation part 8 is By using the observation method, the state of the sample can be observed while applying an in-plane magnetic field and a magnetic field along the coil center axis perpendicular to this. If such a magnetic field generator is used, elements using magnetic bubbles with a diameter of 0.5 μm or less as described above can also be produced.
Its characteristics can be evaluated without being affected by coil heat generation.

(Effects of the Invention) As described above, if the present invention is used, the generated magnetic field strength per unit current is large, so at the same magnetic field strength,
A magnetic field generating device with low power consumption in the coil portion is realized.The frame material of the present invention can be made of not only magnetic ferrite having high magnetic permeability as described above, but also high magnetic permeability metal materials such as permalloy. It is natural from the principle that the effects of the invention can be easily obtained. Furthermore, it is clear that the present invention can be practiced not only with a Helmholtz type magnetic field generating coil in which solenoid type coils are arranged in opposition, but also with a single solenoid type coil.

[Brief explanation of the drawing]

1 to 3 are schematic diagrams showing embodiments of the present invention. In the figure, la and lb are solenoid magnetic field generating coils, 2a and 2b are high permeability magnetic material flat plates, 5 is a sample, and 6
is an in-plane magnetic field generating coil, 7 is a light source section, 8 is an observation section, 10
is the end face perpendicular to the central axis of the solenoid magnetic field generating coil,
12 is a hollow part of the coil, 20 is a coil gap, and 21 is a magnetic field parallel to the coil center axis.

Claims (4)

[Claims] (1) It has at least one solenoid-type magnetic field generating coil, and on an end face perpendicular to the central axis of the solenoid-type coil,
A magnetic field generating device comprising a soft ferromagnetic flat plate having a normal line parallel to the central axis. (2) The magnetic field generating device according to claim 1, wherein the soft magnetic flat plate has an opening in its center that is approximately equal to the inner diameter of the solenoid type magnetic field generating coil. (3) The magnetic field generating device according to claim 1 or 2, wherein soft ferromagnetic flat plates are provided on both end faces of a Helmholtz coil in which two solenoid type magnetic field generating coils are placed opposite each other. (4) The magnetic field generating device according to claim 1, 2, or 3, characterized in that ferrite is used as the soft ferromagnetic material.