A heat-capacity study of the intermetallic compounds R/sub 2/Fe/sub 17/X/sub y/(R=Er, Tm, Gd; X=N, D)

Adiabatic heat-capacity measurements of some of the intermetallic compounds R/sub 2/Fe/sub 17/X/sub y/(R=Er, Tm, Gd; X=N, D) have been performed from 5 K to 350 K. Magnetic ordering phase transitions have been observed at 291.9 K for Er/sub 2/Fe/sub 17/ and at 260 K for Tm/sub 2/Fe/sub 17/. The anomalous enthalpy and entropy of these transitions are much smaller than expected in a pure localized model for the magnetic moments. In Tm/sub 2/Fe/sub 17/ a spin reorientation phase transition of second order character has been observed at 94 K. Theoretical calculations of the free energy and thermodynamic functions have been developed. In the interstitial compounds Er/sub 2/Fe/sub 17/D/sub 3.4/, Tm/sub 2/Fe/sub 17/D/sub 2.13/, Gd/sub 2/Fe/sub 17/N/sub 2.18/ and Er/sub 2/Fe/sub 17/N/sub 2.4/ no anomalies have been observed.<
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