Erbium sample dependence

Fig. 6.9. Temperature dependence of the susceptibility of erbium measured by an AC method in a field of amplitude 6.4 x 10" tesla (after Taylor et al. 1975). Results for the sample warming and cooling are shown. For conversion 1 emu/g = 4irl0 m kg ". ...

Finally, Dodds and Sanny (1978) observed the Er resonance in polycrystalline films which were deposited at room temperature onto fiised-quartz or plexiglass substrates at pressures of approximately 1 x 10" Torr. The nominal erbium concentration varied between 0.2 and 2%. The angular variation of the g-value and linewidth was measured for each sample at a fixed temperature in the liquid He range. During cooling, the difference in thermal contraction between film and substrate produced an effective uniaxial strain in the film. The contraction of the substrate forces the film to expand in the direction perpendicular to the substrate, which becomes the preferred axis and the g-value will depend on the orientation of the field with respect to this axis. In this way even in polycrystalline films an anisotropy of the g-value can be observed. The inferred orbit-lattice coefficients were somewhat smaller than those observed in insulators. They were the same for films on quartz or on plexiglass substrates. This fact supports the conclusion that the strain is macroscopically uniform in contrast to the argumentation of Arbilly et al. (1975). 

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