Calorimetric evaluation of magnetic ordering and spin reorientation in Er3Ge4

Calorimetric measurements have been made on orthorhombic Er3Ge4 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 ln 2 for the ordering of all Er3+ With a ground-state doublet, entropy analysis results in a 30 J/mol energy associated with the spin reorientation process.