Physics of Magnetism

102 CHAPTER 11. MAGNETIC ANISOTROPY

The torque can be obtained by differentiating this equation:

The torque expressions for uniaxial symmetry are simpler and can be derived by

differentiating Eq. (11.1). This leads to

Results obtained in this way by Franse et al. (1989) on a single crystal of the compound

are shown in Fig. 11.5. These measurements were made at 4.2 K. The easy

magnetization direction in is in a plane perpendicular to the hexagonal axis and the

torque was measured in the plane. It can be derived from the results shown that a magnetic

field of 1 T is not strong enough to saturate the magnetization in the hard direction, that is,

in the After Fourier analysis of the curves and comparison with Eq. (11.18),

the following values for the anisotropy constants are found:

and

More extensive descriptions of magnetic anisotropy and its determination can be found

in the textbooks of Chikazumi (1966) and McCaig and Clegg (1987).

References

Chikazumi, S. (1966) Physics of magnetism, New York: John Wiley and Sons.



Durst, K. D. and Kronmüller, H. (1986) J. Magn. Magn. Mater., 59, 86.



Franse, J. J. M., Sinnema, S., Verhoef, R., Radwanski, R. J., de Boer, F. R., and Menovsky, A. (1989) in



I. V. Mitchell et al. (Eds) CEAM Report, London: Elsevier, p. 175.