F. Ono

Magnetization and torque measurements on Nd2Fe14B single crystals

Abstract Magnetization and torque measurements on single crystal specimens of Nd2Fe14B have been carried out. The magnetization values measured always in the direction of easy magnetization and those in the [001] direction have been precisely determined at temperatures from 4.2K to 600K with a superconducting magnet up to 52.65 kOe. Below the spin reorientation temperature 135K, the magnetization value of the direction of easy magnetization increases anomalously with decreasing temperature. The direction of easy magnetization tilts from the [001] axis to the [110] axis and this tilt angle has been also precisely determined by torque measurement in the temperature range below the spin reorientation temperature. The four-fold symmetry in torque curve for the (001) plane is continously observed at even up to near room temperature and the [110] direction of easy magnetization and the [100] direction of hard magnetization do not change below and above the spin reorientation temperature.

Pressure dependence of the Curie temperature in Ni2MnSn Heusler alloy

Abstract Pressure dependence of the Curie temperature in Ni 2 MnSn ferromagnetic Heusler alloy has been examined in a high-pressure region up to 12 GPa by using a double-stage multianvil apparatus. The Curie temperature increased from 65°C at ambient pressure to 122°C at the maximum pressure. The increasing rate decreased above 7 GPa. The tendency can be explained by the interaction curve determined by Kanomaaa et al.

Comparison of magnetic properties of Fe-Pt and Fe-Pd invar alloys with those of Fe-Ni invar alloys

Abstract Temperature dependence of the high-field susceptibility above 300 K for Fe-Pd and Fe-Pt Invar alloys has a strong resemblance to that of Fe-Ni Invar alloys. There exists also a large T 2 term in temperature decrease in magnetization for Fe-Pd and ordered Fe-Pt Invar alloys, similarly for Fe-Ni Invar alloys.

Magnetic properties suggesting a premartensitic transformation in disordered Fe-Pt invar alloys

Abstract An integrated neutron intensity, containing both magnetic and nuclear reflections, shows a hysteresis in the intensity-temperature curve for disordered Fe-Pt Invar alloys, which suggests the existence of a premartensitic transformation in these alloys. This transformation would cause an anomalous change of magnetocrystalline anisotropy constant K 1 , being field dependent and also strongly temperature dependent. The magnetization decreases against temperature more slowly with decreasing Pt concentration, which would be ascribed to the premartensitic transformation.

High-field susceptibility and magnetization in Fe-Ni invar alloys

Abstract The high-field susceptibility of Fe-Ni Invar alloys does not give rise to a sudden increase at the Curie temperature. The decrease in magnetization with increasing temperature is attributed to the T 2 term as well as to the spin wave term for Fe-Ni Invar alloys.

Magnetic field dependence of the magnetocrystalline anisotropy in Fe

Abstract Measurements of the magnetic field dependence of torque curves in pure Fe were made at various temperatures between room temperature and 628 K. A gentle peak was observed in the dK1/dH vs. temperature curve at 360 K. This peak was explained by using the model proposed in former papers of the present author.

The Arrott plots and the itinerant electron character for Fe-Ni invar alloys

In Fe-Ni Invar alloys, the slope of the straight line of the Arrott plots gives 2χ(0, T){M(0, T)}2 from which one can estimate their low field susceptibility, which cannot easily be measured experimentally. The weak itinerant electron character of Fe-Ni Invar alloys can be verified by the fact that the contribution of single particle excitations to the high field susceptibility must be taken into account.

Measurements of lattice parameters in disordered Fe-Pt invar alloys

Abstract By using the X-ray Bond method, lattice parameter measurements have been made in disordered Fe-Pt Invar alloys in the temperature range between 4.2 K and room temperatures. From the observed thermal expansion data the normal lattice contribution and the magnetovolume term due to the longitudinal spin fluctuation were determined.

Permeability change due to stress variation after demagnetization in rayleigh region

Abstract An effective permeability measured in a small alternating field may be changed by changing the stress after demagnetization. A similar phenomenon often takes place when the temperature of magnetic materials is changed instead of the stress variation. This phenomenon may cause an instability of permeability in a weak alternating field.

Pressure dependence of Ms-T curve in GdMn2

Abstract Measurements of magnetization vs temperature curves under pressures have been made in GdMn2 intermetallic compound up to a hydrostatic pressure of 10.7 kbar and a chemical pressure of 14.8 kbar in the low temperature region between 4.2 and 150 K, and the pressure dependence of the Neel temperature of the Mn-sublattice was determined. By using data for the pressure dependence of the lattice parameter, the critical pressure of 14.8 kbar, below which the Mn sublattice magnetic moment disappears, was converted to the critical lattice parameter of 7.6A. This value is in excellent agreement with the results of Yoshimura et al.