Holmium magnetic structure

The holmium ions order antiferromagnetically in the HoRu2Ge2 compound at the Neel temperature T = 20K. This compound exhibits a square modulated structure with a propagation vector k = (0.2216, 0.0111, 0) and a holmium magnetic moment of 6.6 parallel to the c-axis (Yakinthos and Roudaut 1987). 

Figure 9.17 Plot of the in-phase and out-of-phase AC magnetic susceptibility for the complex [SmFe] at driving frequency of 199 Hz and 355 Hz [98]. (Reprinted with permission from B. Yan, and Z. Chen, Cyano-bridged aqua(A, Al-dimethylacetamide)(cyanoiron)lanthanides from samarium, gadolinium, or holmium nitrate and potassium hexacyanoferrate crystal structures and magnetochemistry, Helvetica Chimica Acta, 2001, 84, 817-829 (Figure 7). Wiley-VCH Verlag GmbH Co. KGaA.)...

In fig. 3.22 the data on holmium in two different directions and at two different temperatures are shown. The near parabolic shape for the data along the b axis indicates that there is more symmetry in the Fermi surface around the hexagonal axis. However, the surface is not spherical because the data deviate considerably from the free electron theory. The slight temperature dependence of the c axis data for Ho reflects the change in band structure and Fermi surface due to magnetic ordering. 

Holmium orders magnetically at 133 K to form a bassd plane spiral structure with an interplanar turn angle decreasing monotonically from 50° at Tn to 36° at 35 K, below which it drops steeply to 30° at Tc = 19 K. The neutron diffraction study of Koehler et al. (1966) revealed, below Tc, a ferromagnetic c-axis moment of IJ /ib - the moments lift out of the plane by some 10° to form a conical structure. 

The 4.2 K magnetization measurements of Bozorth et al. (1972) support these results. Figure 6.8 illustrates how a field applied along the c-axis closes up the cone, after initial 180° domain reversals (as in the case of holmium). Rhyne et al. s (1968) results are similar but some 3.7% higher. The successive modifications of the spin structure, produced by a field in the basal plane, are reflected in the magnetization curves. At = 2.0 T, the distorted spiral... 

---