Basal plane anisotropy dependence

Fig. 18. Temperature dependence of the magnetization of a LuNi2B2C single crystal in a field of 3 T applied along the crystallographic directions c, a and (110), clearly showing an out-of-(tetragonal basal) plane anisotropy as well as an in-plane anisotropy of Hc2 where Hc2(T) is determined by the indicated linear extrapolation (after...

Fig. 10. Applied field dependence of the = 0 magnon energy gap in Tb—10%Ho demonstrating the validity of the frozen-lattice strain approximation as manifested by the minimum, but non-vanishing, of the gap energy at a held corresponding to the basal plane anisotropy held. Data taken with the field along the hard basal plane direction, except for the curves marked easy (axis) which show a linear increase of gap energy with field. The lines are theoretical curves. Different symbols are used to distinguish data taken at different temperatures. (After Nielsen et al. 1970b.)...

Following the /-dependence of the appropriate Stevens factor, Dy exhibits a crystal field contribution to the basal plane anisotropy considerably larger than Tb and, as already noted (section 2.2.2), the a-axis is the easy direction so that If is negative. Although Feron et al. estimated kI from 1.7 to 105 K, below 50 K the available magnetic field was insufficient to pull the magnetization completely into the hard direction. Thus the extrapolations used to calculate K6(0) = -1.1 0.1 X 10 Jm should be treated with caution. 

Both Rhyne and Feron estimated kKO) as 2.7 0.3 x 10 Jm whilst Cock (1976) deduced a value of 3.4 0.3 x 10 Jm The basal plane anisotropy in Ho is thus larger than in any other lanthanide, a result of the 4f charge distribution associated with the large orbital moment (L = 6). As in the case of k , the temperature dependence of kI cannot be readily parameterized and requires further investigation. 

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