Magnetic properties of ErFe2Al10 and ErRu2Al10 single crystals

We investigated the field dependences of magnetization M(H), the temperature dependences of magnetic susceptibility χ(T), and specific heat C(T) of orthorhombic ErFe2Al10 and ErRu2Al10 single crystals in a temperature range of 0.46–300 K. For ErFe2Al10, an antiferromagnetic phase transition was observed at the Néel temperature TN 1.7 K, and M(H) of the b-axis at 0.47 K indicated a metamagnetic transition at 0.07 T. The easy axis in M(H) and χ(T) curves is the b-axis and the hard axis is the c-axis. A large anisotropy was seen in M(H) and χ(T) curves in the three crystal axes. In the case of ErRu2Al10, magnetic successive phase transitions were observed at 1.3 and 1.0 K. Spin-flops were observed in M(H) curves at 0.25 T on the a- and b-axes in 0.46 K. The easy axis in M(H) curves is the a-axis and the hard axis is the c-axis. We proposed a magnetic structure from the result of χ(T) curves, whereby the magnetic moment of Er was perpendicular to the c-axis and closely aligned to the [110] direction below TN. The C(T) curve showed sharp peaks at corresponding temperatures. For both compounds, hump structures were observed in the temperature dependences of magnetic specific heat above TN. These structures were Schottky anomalies that came from excited doublets.