Basal plane anisotropy temperature

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.)...

Lounasmaa and Sundstrom (1966), in view of the strong basal plane anisotropy of Tb at low temperatures, favoured introduction of a spin-wave energy gap as against a simple power law for Cm. They found a reasonable fit with Cm = 36 r exp(-23.5/T) from 8 to 20 K, based on the assumption Ce+Cl = Cp (Lu). In their analysis, Wells et al. (1976) used a theoretical expression... 

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. 

The calculated value dPsr/dP = —4.9K/kbar is in accordance with the measured one. The pressure effect on the anisotropy constants was studied by Mihai and Franse (1976), Franse and Mihai (1977) and Toyama et al. (1969). The experiments showed that dK /dP > 0. Franse and Mihai determined the direction of the magnetic easy axis with the help of a torque magnetometer. It was shown that below Pgr the magnetic moment lies in the basal plane. At temperature = lOOK the angle 0 begins to decrease reaching the value of 45 at P = OK. The temperature interval APjr = — Psr expands under... 

The specific resistance of natural graphite crystals is ca Hem (room temperature) along the a axis parallel to the network basal plane. The resistance along the c axis (perpendicular to the basal plane) is ca 1 Q. The cja axis anisotropy ratio is, therefore, ca 10 . Screw dislocations within the crystal may short-circuit the current path parallel to the c axis and cause lower anisotropic ratios separation of planes may cause higher anisotropic ratios. 

X-ray diffraction analysis of the samples sintered from powder A has shown that theoretical density decreases with the growth of the sintering temperature, while the experimental values increase. At the same time lattice parameter a increases and parameter c decreases under the sintering temperature higher than 1200°C, i.e. the anisotropy of the TiB2 lattice decreases. Apparently this is caused by different value of compressibility of the lattice in basal plane and direction of hexagonal axis. 

---