Calorimetric evaluation of magnetic ordering and spin reorientation inEr3Ge4

Abstract

Calorimetric measurements have been made on orthorhombic ${\mathrm{Er}}_{3}{\mathrm{Ge}}_{4}$ having two crystallographically distinct Er sites. The temperature dependence of specific heat shows a peak near 7 K, confirming the antiferromagnetic ordering of both Er sublattices as suggested by neutron diffraction. A spin reorientation in one of the Er sublattices of the highly canted magnetic structure prevails as a second peak in specific heat around 3.5 K. Both magnetic transitions exhibit no thermal hysteresis. By further taking into account the relatively small contributions from lattice and crystal-field effect, as well as $3R\mathrm{ln}2$ for the ordering of all ${\mathrm{Er}}^{3+}$ with a ground-state doublet, entropy analysis results in a 30 J/mol energy associated with the spin reorientation process.