SPECIFIC HEAT OF YFe₃(BO₃)₄, Y_0.5Gd_0.5Fe₃(BO₃)₄, AND GdFe₃(BO₃)₄
Vasiliev A.N., Popova E.A., Bezmaternyckh L.N., Temerov V.L., Hiroi Z.

Received: July 14, 2005

PACS: 75.40.Cx

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The specific heat was measured in the range 0.4-300 K in YFe₃(BO₃)₄, Y_0.5Gd_0.5Fe₃(BO₃)₄, and GdFe₃(BO₃)₄ single crystals. Sharp anomalies were found at temperatures of first-order structural, second-order antiferromagnetic, and first-order spin-reorientational transitions. The Neel temperature of about 37 K was found to be virtually independent of presence of rare-earth ions, indicating rather weak coupling of Gd and Fe subsystems. The contribution of the magnetic system to specific heat was separated through the scaling procedure allowing determination of the magnetic entropy of Fe and Gd subsystems. At the lowest temperatures, the specific heat in GdFe₃(BO₃)₄ exhibits a Schottky-type anomaly, which is due to Gd³⁺ eight-fold degenerate ground level splitting by the internal magnetic field of the Fe subsystem of about 7 T.