Mitita Goto

Magnetic Properties of the Amorphous Alloy System (Fe1-xNix)77Si10B13

The saturation magnetic moment µs, the Curie temperature Tc, and the high temperature susceptibility were measured in the amorphous alloy system (Fe1-xNix)77Si10B13. The measurements were done for temperatures above 77 K. The variation of µs and Tc with x were similar to that in other (Fe-Ni)-amorphous systems so far reported. The susceptibility was measured for specimens with 0.6x1.0. Ni77Si10B13 or x=1.0 was found to have Pauli type paramagnetism with χg=2×10-6 emu/g over the temperature range 77-500 K. The susceptibilities for other specimens followed the Curie-Weiss law well, and so the Curie constant Cg, the effective magnetic moment µeff, and the asymptotic Curie temperature Θ were determined. Cg, µeff, and Θ decreased so as to vanish at x~1.0.

Magnetic Properties of the (Fe1-xMx)3P Compounds

The crystal structure, magnetic transition point and saturation magnetic moment were determined for (Fe1-xMx)3P compounds with M=Cr, Mn, Co, Ni. X-ray examination identified all the compounds as b.c.t., except Mn compounds with 0.3 0.3 could not be prepared. Antiferromagnetism was found in Mn compounds with x>0.3. The concentration dependence of lattice constants indicates that, in the range of small x, the substitution occurs preferentially at a specified site. The saturation moment at 4.2 K decreases almost linearly with increasing x, but with a different slope depending on the substituted elements. The result was discussed based on the assumption of the preferential substitution.

Magnetocrystalline Anisotropy in Quenched and Annealed Fe3Si

Magnetocrystalline anisotropy constant K 1 of Fe 1- x Si x (0.08≤ x ≤0.25) in both as-quenched and after-annealed samples was determined from torque measurements in 77∼300 K, in order to make clear the difference in K 1 between disorder and order phase (D0 3 type) of Fe 3 Si at x =0.25. The difference in K 1 between both the cases began to appear at x ≃0.17, and values of K 1 for x =0.25 were determined to be - 1.01× and 0.94×10 5 erg/cm 3 at 77 K in the as-quenched and the after-annealed, respectively. This difference in K 1 was apparently due to the one in the degree of order in D0 3 ; the former value was thought to be of nearly perfect disorder in long range and the latter of perfect order. In any case, it was concluded that K 1 of Fe 3 Si is negative in disorder and positive in order (D0 3 ).

Forced Volume Magnetostriction of Ni-Cr Alloys

The temperature dependence of forced volume magnetostriction dω/d H for Ni 1- x Cr x alloys ( x <0.1) has been measured by strain gauge technique. The values of dω/d H for Ni, 1.9 and 3.9 at%Cr-Ni change their sign from positive to nenative at T / T c =0.7, 0.75 and 0.85, resrectively. Those for other Ni-Cr alloys measured are positive at all temperatures. The pressure coefficients of the magnetic moment per unit mass at 0 K, d ln σ s0 /d p , determined from the present data by using thermodynamic relations are all negative and become larger in the absolute value with increasing x . These results suggest that the s - d transfer is dominant according to Mathons procedure based on the itinerant electron model. The pressure derivatives of T c , d T c /d p , obtained from the present data agree with direct measurements and their sign changes from positive to negative at about 6 at%Cr-Ni with increasing x .

Contribution of the Magnetoelastic Term to the Effective Magnetic Anisotropy Constant K1 for Nickel

The contribution of the magnetoelastic term ( K 1 ) M.E. to the effective magnetic anisotropy constant K 1 has been evaluated for Ni using the published data on elastic constants and the magnetostriction constants redetermined in the present measurement. Measurements were done with the (001) and (011) disks by means of the strain gauge technique. At high temperatures where the sign of K 1 is positive, the sign of ( K 1 ) M.E. is positive and the magnitude is a little larger than that of K 1 . The change in sign of K 1 from negative to positive with a rise in temperature is therefore ascribable to ( K 1 ) M.E. , and the intrinsic magnetic anisotropy constant ( K 1 ) 0 (= K 1 -( K 1 ) M.E. ) decreases monotonically in magnitude without accompanying any change in sign, as temperature rises up to the Curue temperature T c .

Forced Volume Magnetostriction of Disordered Ni-Mn Alloys

The temperature dependence of the forced volume magnetostriction dω/d H of disordered Ni 1- c Mn c alloys ( c <0.25) has been measured by strain gauge technique. The values of dω/d H for Ni and 4.8 at%Mn change the sign at T / T c =0.7 and 0.9, respectively, but those for the other Ni–Mn are positive at all temperatures. The pressure coefficients of magnetic moment at 0 K dln σ s0 /d p estimated thermodynamically are all negative and become larger with increasing c . The values of dln σ s0 /d p are approximately proportional to the high field susceptibility χ hf at 4.2 K. The estimated pressure derivatives of the Curie temperature d T c /d p also change the sign to negative with decreasing T c , and agree well with the direct measurement. These results for the pressure effects are discussed qualitatively with the competition between the d -band widening and the s - d transfer in itinerant electron model.

Pressure Effects Estimated from Forced Volume Magnetostriction for Ni–Tm [Tm=Ti, V, Cr, Mn] Alloys

The temperature dependence of forced volume magnetostriction dω/d H for Ni 1- x Ti x ( x ≤0.1) and Ni 1- x V x ( x ≤0.08) alloys has been measured using the 3-terminal capacitance method. The values of dω/d H for Ni ∼8 at%Ti-Ni and ∼6 at%V-Ni alloys change their sign from positive to negative with raising the temperature. Pressure coefficients, d ln µ/d p and d ln T c /d p , have been deduced from the temperature dependence of dω/d H using the thermodynamical and the Kornetzki-Kouvel relations. The relation between two pressure coefficients above are analysed according to Inoue and Shimizus discussion. The values of the coefficient C /χ hf T c obtained decrease gradually from 2 to 1 with decreasing T c toward 0 K for both alloy systems.