Co based amorphous films were plated from the bath with phosphorus acid as a metalloid source. The amorphous films with a thickness of about 1μm were successfully fabricated by peeling from a smooth electrode which was mirror-finished so that the center line average roughness was less than 0.5μm. Magnetic properties of these very thin films were examined and a discussion was developed for the relationship between the thickness of the films and the high frequency magnetic properties. The initial permeability of the film with 1μm thickness was high and constant value 3000 at a frequency of up to 10 MHz. Furthermore, the value of tan δ was exceedingly small.
Mössbauer studies were carried out to clarify the magnetic structure and the formation process of α"-Fe16N2. To obtain α"-Fe16N2 samples, thin iron films were nitrified by a multiple implantation of nitrogen ions, followed by vacuum annealing at 150°C for 2 or 60 hours. Their Mössbauer spectra were decomposed into three sextets originated from three sites of Fe in α"-Fe16N2, and one of residual α-Fe. It was found that the nitrogen ions tend to order, so as to form α"-Fe16N2. Because of the tendency, the iron nitride has a structural resemblance with α"-Fe16N2 since ions were implanted. The annealing was effective to an additional improvement of the nitrogen order and a relaxation of internal stresses. Magnetic moment of each Fe atom corresponding to the three sextets was obtained to be 1.3, 2.5 and 3.8 μB, respectively. In α"-Fe16N2, the first neighbor Fe atom of nitrogen yields the least moment, and the third one yields the maximum moment.
A YBCO superconductor prepared by a Melt Powdering Melt Growth (MPMG) method was investigated with respect to the feasibility for an application to a superconducting current lead. A thermal conductivity and a critical current density of the YBCO sample were measured in the temperature range from 50 K to 15 K. The value of the thermal conductivity was about 0.03 W/cmK at 50 K. In the sample with a cross section of 8.65 × 6.85 mm2 and a thickness of 2.25 mm, the maximum quench current at 26 K was 86 A of which the value was one of few tens of the value expected from the critical current density, about 3000 A/cm2. The contact resistance at the current junction was relatively high, about 0.5 mΩ. Obtained results indicate that the MPMG bulk is a hopeful material for a superconducting current lead.
We have observed that gas-flow can be blocked or disturbed by magnetic fields. To exaplain this phenomenon, we developed a model called a “magnetic curtain” based on the paramagnetic properties of the oxygen molecule. In this paper, we applied this phenomenon to the control of heat transport in heat pipes. We used a heat pipe 20 mm in diameter and 500 mm in length packed with oxygen as a working fluid. We positioned this device vertically in an airgap 70 mm wide between the poles of an electro-magnet with 240 mm in diameter, in the direction perpendicular to the axis of the magnetic poles. The top side of the heat pipe was chilled with liquid nitrogen (77 K), and the lower side of the heat pipe was exposed to room temperature (290K). When the middle part of the heat pipe was exposed to magnetic fields of 1.0 T with the gradient of 5～50 T/m, the heat transport was blocked.
We investigated the minor M-H loop focussing especially on the third harmonic component in the loop and its DC-bias magnetic field for a sintered Y-Ba-Cu-O superconductor disk. We found that; (1) the minor loop is a Rayleigh type, (2) the Rayleigh constant depends on the DC-bias field and shows a singular magnetic hysteresis, and (3) the hysteresis is symmetrical when the sample is cooled under zero-magnetic field, whereas it is asymmetric when it is cooled under a magnetic field. These phenomena are qualitatively explainable using the critical state model.
A measurement method of the saturation magnetostriction constant is introduced. The magnetostriction was determined without using the thickness and Young's modulus of the films. The annealed film deposited on a substrate which has the uniaxial anisotropy of thermal expansion has the magnetic anisotropy induced by thermal stress. The stress anisotropy was determined by interpolation or extrapolation. And the magnetic anisotropy induced by magnetostriction was measured from B-H loops. The saturation magnetostriction constant was derived from the relation between these two types of anisotropy.