The Magnetic and Electric Properties of (Co_<1-x> Mn_x)_2B Crystalline compounds and Amorphous Alloys

The manganese concentration x dependence of the average magnetic moment μo, the Curie temperature Tc, the pressure effect on Tc and the electric resistance for the ferromagnetic amorphous alloys (Co_ Mn_x)B were investigated. The Curie temperature decreases linearly with increasing x and μo had a maximum around x=0.15. The magnetic susceptibility vs. temperature curves for all the prepared amorphous alloys obey the Curie-Weiss law above Tc. The pressure effect on Tc is that Tc has a value of 1.06 K/kbar at x=0 and is decreasing with increasing x and becomes zero at x=0.4. These results are analyzed on the basis of the pair interaction model and the local enviroment effect. There arise two kinds of minimum in the resistance vs. temperature curves. That the resistance minimum at high temperature has a strong correlation with Tc is assured by measuring the transverse effect of the resistance with amorphous alloys x=0.4. The resistance minimum for the amorphous alloys and crystalline compounds are found at low temperature under ferromagnetic state

High Field Magnetization in Manganese Intermetallic Compounds(Magnetism)

Magnetization measurements were carried out on manganese intermetallic compounds Mn_3MC(M=Ga, Zn), Mn_Co_xSb(x=0.09 and 0.15) and MnMX(M=Ru, Rh, Pd;X=As, P)in magnetic fields up to 150 or 320 kOe. Antiferromagnetic(AF)-ferromagnetic(F) field-induced transitions and (AF+F)-(F) one were observed for Mn_3GaC and Mn_3ZnC, respectively. For Mn_Co_Sb, intermediate(I)- ferrimagnetic(Fr) field-induced transitions were observed. For Mn_Co_Sb, AF-Fr field-induced transitions were observed. These transitions were of the first order except one of Mn_3ZnC. The magnetic properties of MnMX (M=Ru, Rh, Pd;X=As, P) were discussed on the basis of the values of magnetization and high-field magnetic susceptibility

High Pressure Apparatus for Angle Dispersive Neutron Diffraction

A piston-cylinder type high pressure apparatus was designed for the angle dispersive neutron diffraction. A Ti-53wt% Zr alloy was used for the cylinder. The performance was tested by observing the structural transformation under pressure in RbBr from an NaCl-type to a CsCl-type

The Change of Curie Temperature of Ordered Au_4Mn and the Indium Heusler Alloy by Hydrostatic Pressure

The change of Curie point by the application of hydrostatic pressure of 3 katm. to the Indium Heusler alloy as well as the intermetallic compound Au_4Mn was measured. It was found that the rate of change took positive value 1.5×10^ and 2.7×10^ deg/kg/cm^2 for Heusler alloy and Au_4Mn respectively. It was also elucidated that the change of absolute saturation of magnetization for both alloys was negative, -2.1×10^ and -7.2×10^ cm^2/dyne respectively

A High Pressure Apparatus for Neutron Diffraction

A high pressure apparatus was developed for thermal neutron diffraction of time-of-flight method. The high pressure vessel was a piston-cylinder type, and Ti-Zr alloy was used as a material of the cylinder. The coherent scattering of neutron is suppressed in Ti-53wt% Zr alloy. The diffraction spectrum is formed of peaks from the specimen and a background, which corresponds to the energy distribution of the incident neutron. High pressure measurements were made in RbBr on the transformation between NaCl-type structure and CsCl-type to a pressure about 20 kb, and a good agreement was confirmed with former experiments

Effect of Pressure on the Curie Temperature of CrTe and MnSb Compounds of the Nickel Arsenide Type

The effect of the pressure on the Curie temperature of CrTe and MnSb compounds of the nickel arsenide type structure were studied up to 4, 000 kg/cm^2. The rate of change of the Curie temperature was -5.5×10^℃ kg^cm^2 for CrTe and (-3.2±0.5)×10^℃ kg^cm^2 for MnSb. From the result of the present experiment, the critical pressure and temperature to realize a first kind transition from a ferromagnetic to a paramagnetic state in CrTe are evaluated to be 41, 000 kg/cm^2 and 107°K, respectively

On the Magnetostriction of Au_2Mn at High Magnetic Fields

The magnetostriction of an antiferromagnet Au_2Mn of the screw type spin arrangement was measured up to a magnetic field intensity of 80 kOe in the temperature range from room temperature to the liquid He point. Both the longitudinal and transverse magnetostriction curves consist in series of (1) a fairly complicated part in a low magnetic field range, (2) a contraction of the order of 200×10^, and (3) a weak contraction proportional to the intensity of the magnetic field in a high field range. At temperatures above 200°K, slight expansion can be seen between the stages (2) and (3) in the case of the longitudinal effect. The observed magnetostrictions can be considered to be caused by (1) the rotation of the magnetic moment in the c-plane, (2) the rotation of the magnetic moment toward the c-axis, and (3) the change in screw angle during the course of magnetization

Heat Capacity of Pd-Si, Ni-Si-B and Zr-Based Metallic Glasses

The specific heat of metallic glasses containing Si and B (Ni_Si_B_ and Pd_Si_) and Zr-based metallic glasses(Zr_Al_Cu_Ni_Co_, Zr_Al_Cu_ and Zr_Cu_) was measured in the temperature range 77-800 K using an a.c. calorimeter. Several exothermic and endothermic processes were observed correspondingly to the transformation sequences for complete crystallization of all the glasses. The structural relaxation process appears with a decrease in heat capacity. For Ni-Si-B and Pd-Si glasses an abrupt increase in the specific heat is observed at the glass transition temperature T_g. For Zr-based glasses, however, a monotonous increase in the specific heat is observed just below T_g. Then the specific heat makes a peak and decrease abruptly with increasing temperature. The height of the peak increases with heating rate

Pressure Effect on the Magnetic Transition in Mn-Compounds

In the ferromagnetic compounds Ni_2MnSn (Heusler type) and PtMnSn (C1_b-type), the sign of the spontaneous volume striction is measured as negative and dT_c/dP is positive. The signs are opposite to those in NiAs-type Mn-compounds, in which the Mn-Mn distance is comparatively small. These facts are discussed on the basis of an argument that the ferromagnetic interaction is stabilized by contraction or extension of the Mn-Mn distance to adjust the overlapping of d-shells