Antiferromagnetism and Metamagnetism in ErFeCuGe4O12

Magnetic properties of GdBB′Ge4O12; BB′ = FeZn or GdCa

“…The transition temperature is higher than those of ~4 K reported previously for Gd2CoGe4O12, GdScCoGe4O12 and GdLuCoGe4O12 [8] and it approaches, but remains below, the transition temperatures, 15 ≤ T/K ≤ 17, observed in AMnFeGe4O12 (A = Y, Eu, Lu). It is also lower than that of the more magnetically-concentrated composition ErFeCuGe4O12 [9]. The magnetic superexchange pathways that might be important in this crystal structure have been described in detail elsewhere [4].…”

“…In this case those compounds that underwent a magnetic transition did so at a temperature below 4 K and the interpretation of our data was consequently complicated by the interplay of crystal-field effects and spin-orbit coupling. More recently [9] we have described the behaviour of the magnetically-concentrated composition ErFeCuGe4O12 which orders antiferromagnetically at 20 K and undergoes a metamagnetic transition, driven by the single-ion anisotropy of Er 3+ , in a field of 20 kOe at 2 K. Similar transitions have been seen in compositions with anisotropic Co 2+ cations on the 4f sites [6]. In order to eliminate the consequences of orbital angular momentum and spin-orbit coupling we have begun to prepare compounds containing only spherical magnetic cations.…”