JPS5951121B2 - Cylindrical domain material - Google Patents

Description

Detailed Description of the Invention The present invention uses germanium or silicon instead of potassium in a garnet material for a cylindrical magnetic domain element, and in order to compensate for the ion valence, a +2-valent cation (Ca) is added to the rare earth ion position. Among the materials put in, Sm ions and Tm ions are included as rare earth ions, and the respective concentrations y and z are 0.15≦y≦0.3 and 0.2≦z≦, respectively.
0.6, and Ca concentration X is 0.6≦X≦0.95
This relates to a cylindrical magnetic domain material.

Currently, cylindrical magnetic domain elements are attracting attention as elements that have the potential to open up a new phase in the information processing industry.

However, in order for this device to develop significantly in the future, further development of materials is desired. First, it has become important to increase bit density. As a result, composite rare earth iron garnets have attracted attention. In these garnets, the rare earth ion concentration is kept to the minimum necessary to increase the bubble movement speed. The minimum required amount is related to the limit value of the uniaxial magnetic anisotropy energy that determines the stability of the bubble. The bubble diameter is defined by the characteristic length (1) of the material. l can be expressed as = -2(1) 4πMo using domain wall energy density (σw) and saturation magnetization (Ms).

In order to create a material with a small bubble diameter from the mountain type, l must be made small. For this purpose, the material's 4πMs
must be increased or σw must be decreased. Furthermore, the conditions for becoming a bubble material include a uniaxial magnetic anisotropy field (Hk), 4πMs, and Hk>4πMs. In other words, the q value determined by the following formula is 1
It has to be bigger.

q=-(2)πMs Currently, it is becoming important to increase the bit density by making the bubble diameter as small as possible from the viewpoint of mass production, cost, etc.

The following three points must be considered as conditions for improving bubble stability when the bubble diameter is reduced.

(a) The ratio of the characteristic length (1) to the domain wall width (lw) should be the same as the current 8 μm bubble material.

In other words, q≧3.5. (b) If 81 is taken as the bubble diameter, 81<3.0 μm.

(c) 4πMs should be made as small as possible in order to make the driving magnetic field (Hr) as small as possible.

11. The relationship between q value is l=(2A/πMmi)”←”q”←” (3).

A is the exchange interaction constant, here 2×10-7Erg
/Cm.

Then, when material properties are determined so as to satisfy the conditions q≧3.5 and 81=bubble diameter, the smaller the bubble diameter is, the larger 4πMs must be. For example, for a 3 μm bubble, 4πMs must be 250 Gauss or more. As 4πMs is increased in this way, the bubble disappearance magnetic field (HcOl) also becomes higher.
4 with a material containing the same elements as the material when the bubble diameter is large.
When only πMs is increased, the Curie temperature of the material also increases accordingly. Such a tendency has a great influence on the temperature characteristics of device performance when assembled as a device.

Currently, barium ferrite is being considered as a ferromagnetic material for bias magnetic fields used in devices, but the temperature coefficient of its residual flux density (Br) is around room temperature, and its change is in the range up to around 100°C. It is known that it is linear over . Therefore, the bubble's vanishing magnetic field (HcOl)
One of the requirements for the material is that the temperature condition is -0.19%/Deg. However, the relationship between the bubble diameter and 4πMs in the above-mentioned materials is based on bubble extinction. This brings about the bubble diameter dependence on the temperature dependence of the demagnetizing field. This dependence on bubble diameter is such that in a garnet containing non-rare earth ions as a main component, the temperature characteristics become worse as the bubble diameter becomes smaller in the temperature range of 0 DEG C. to 100 DEG C. For example, 3
Regarding μm bubble diameter materials, in the case of S, the temperature characteristic of the bubble disappearance magnetic field is -0.19% near room temperature without using rare earth ions with 7 or more electrons packed in the 4f shell.
/Deg, and it has been difficult to obtain a material whose change is linear over the temperature range from 0°C to around 100°C. In consideration of the above points, the present invention uses a thulium ion with 12 electrons in the 4F shell among rare earth ions to generate a bubble extinguishing magnetic field (HcOl) temperature near room temperature in a micro bubble of 7 μm or less. The present invention provides a material having characteristics of -0.19%/Deg and in which the temperature change of HcOl is linear in the temperature range from 0°C to around 90°C.

This will be explained in detail below using examples. Figure 1 shows Y3-X
-y-ZCaXSmyTmZ, Fe5-XGeXOl2
7μm bubble made of garnet 4μm bubble and 2
It shows the temperature dependence of the bubble disappearance magnetic field HcOl of μm bubbles.

1, 2, and 3 in FIG. 1 are the measurement results for 7 μm bubbles, 4 μm bubbles, and 2 μm bubbles, respectively. z in these materials is 0.3, 0.4 and 0 respectively
．． It was 55. The reason why z must be increased as the bubble diameter is decreased is related to the increase in the Curie temperature of the material. Note that y is fixed at 0.25. X increases as the bubble diameter increases, and is in the range of 0.8≦X<0.9. These 3
The temperature characteristics of HcOl for the two materials are - around room temperature, respectively.
0.18, -0.19, -0.19%/Deg,
And 0. HcOl in the temperature range from ℃ to around 90℃
The change in was almost linear. By changing the amount of Ge in the film to adjust the 4πMs of the material and adjusting the amount of thulium ion replacement, the temperature characteristics can be adjusted to the residual magnetic flux density (B) of barium ferrite for bias magnetic fields.
We present epitaxial garnet films for bubble devices with bubble diameters from 7 μm to 2 μm, which are made of materials tailored to the temperature characteristics of r). The epitaxial film was fabricated using a liquid phase epitaxial method using the same depping method used to grow rare earth garnet films.

Claims (1)

[Claims] 1 General formula Y_3_-_x_-_y_-_zCa_xS
m_yTm_zFe_5_-_xM_xO_1_2(M
In the garnet epitaxial film for a cylindrical magnetic domain element represented by Si or Ge, the concentration y of samarium (Sm) is 0.15≦y≦0.3, and the concentration z of thulium (Tm) is 0.2≦z≦0. .6, and the concentration x of calcium (Ca) and germanium (Ge) or silicon (Si) is 0.6≦x≦0.95.