Magnetocrystalline anisotropy nickel - vanadium alloys

Abstract

Single crystals of 5N and 4N pure Ni and a series of NiV alloys up to 6.72 at % V were grown and cut into spheres and blocks for anisotropy, magnetization and resistivity measurements. Measurements of the first anisotropy constant of these crystals were made between 4.2 and 300K using a torque magnetometer. All the measurements were performed when the magnetic field of up to 11 k0e could rotate in a (001) plane. Corrections for the effect of the higher order constant K(_3) on the torque curves were found to be necessary in the case of pure Ni and 0.98% alloy. Using a Faraday balance the magnetizations of the crystals of higher vanadium content were measured from 77K to room temperature. Values of M at 4.2K were measured to check the validity of the extrapolation of these results to OK. Using a D.C. method it was possible to measure the values of the resistivity of these samples from 4.2K to room temperature. In addition crystals of Ni Mo with 1 at % Mo and of NiV with 12.5 at % V were grown and their resistivities were measured from 4.2K to room temperature. Using the results from anisotropy measurements it was possible to show that variations of temperature or of concentration affect the first anisotropy constant in a similar manner. This is in good agreement with the results on Ni Mo of Hausmann and Wolf (1971). The results from anisotropy and resistivity measurements were combined to check whether the hypothesis suggested by Hausmann (1970) were true. This was found not to be so even though the relationship was examined for a wide range of temperature. Combining the results of anisotropy and resistivity measurements it has been found that there is further support for the suggestion by Franse et al. (1973) of a link between temperature variation of anisotropy and the minority spin resistivity in accord with the work of Furey. There remains some doubt about the correctness of the method of distinguishing between majority and minority spin resistivities. The temperature variation of K(_1) and M was also examined and the value of n found in equation K(T,C) = K(O,C) [ M(T)/M(O) ](^n) in the case of NiV crystals is less than that for pure Ni and it decreases as the concentration is increased.