Magnetic Anisotropy Fields in Single-Crystal Iron Garnets

摘要

Measurements of the temperature dependency of firstand second-order anisotropy fields, as well as g-factors, have been made on single crystal iron garnets of yttrium, lutetium, gallium-yttrium, and indium-yttrium. Unit formulas are denoted by Y3Fe5O12, Lu3Fe5O12, YeFe(5-z) Ga(z)O12, and Y3Fe(5-z)InzO12, respectively. Results show that at any given temperature, first-order anisotropy fields within the yttrium iron garnet are enhanced by the substitution of gallium and diminished by the substitution of indium, and that for any given sample, these fields increase as temperature is lowered. Low temperature anisotropy fields for lutetium iron garnet, while completely at variance with those previously reported, are as expected. However, the anisotropy surface of lutetium iron garnet is highly convoluted at liquid helium temperatures. Also, there is evidence that anisotropy fields are independent of sample size effects. No experimental evidence of effects due to an external electrostatic field or of thermal hysteresis could be detected. Secondary peaks observed superimposed on the principal resonance absorption curve of some of the samples over many temperatures are noted. Derivations are given of the cubic system anisotropy energy and Kittel's 'effective demagnetization factors' in the (110) plane up to third order. (Author)