Specific heat of some rare earth iron garnets and yig at low temperatures
Heat capacity measurements of the iron garnets of Y, Gd, Er, Ho, and Yb between 1.4°and 20°K are presented. Below 5°K, the specific heat of YIG can be represented by the sum of a lattice term proportional to T 3 and the spin-wave contribution 2.15 × 10-3T 32 joules/mole-deg. This last term agrees satisfactorily with that calculated from a spin-wave analysis, in which the exchange interaction coefficients were those derived from Pauthenet's magnetization data. The results of the magnetic specific heat of the rare earth ions could be interpreted in terms of a Weiss molecular field acting on these ions. For Gd3+ and Yb3+, this field was found to be, respectively, about 3.0 × 105 and 1.5 × 105 oe below 20°K, in satisfactory agreement with that derived from Pauthenet's data. © 1960 The American Institute of Physics.
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