The ferromagnetic anisotropy of electrical resistivity (FAR) has been measured at 300 and 77 K, together with the saturation magnetization n
B, the Curie temperature and the temperature coefficient of resistivity (TCR), for a large number of (Fe-Co-Ni)-X alloys in fcc, bcc and amorphous phases. Several empirical rules are presented. (1) The FAR is found to be correlated not only with n
B but also with the resistivity. In the low-resistivity regime the FAR reaches a maximum at about n
B=1.0. The maximum becomes suppressed with increasing resistivity. In the high-resistivity regime, into which the amorphous alloys are grouped, the FAR increases monotonically with increasing magnetization. (2) The FAR value decreases rapidly with increasing resistivity. The value in the amorphous phase is one to two orders of magnitude smaller than that in the low-resistivity alloys. (3) Both FAR and TCR are closely interrelated; an increase in the FAR is always accompanied with an increase in TCR.
An improved method is proposed of determining magnetic anisotropy constants for Alnico monocrystals subjected to the optimal field treatment. The magnetic torque curves are measured for the (001) disk specimen in various intensities of magnetic field, and then they are resolved by a harmonic analysis to obtain the Fourier coefficients. By postulating a uniform precipitate structure in the specimen, the formulae can be derived by which the uniaxial shape anisotropy constant as well as the cubic crystalline anisotropy constant can be separately evaluated with due consideration for a field dependence of the coefficients. For an Alnico 5 monocrystal treated in the optimal condition, the erg/cm3, respectively. Furthermore, similar measurements are made on Alnico 5 specimens fieldtreated in some directions deviating from the cube axis. These results can reveal the limitations on applications of the present method.
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