Unusual magnetocaloric effect in R2Al (R = Dy, Ho, Er) compounds

The magnetic properties of the orthorhombic intermetallic compounds R2Al (R = Dy, Ho, Er) are reported. Dy2Al undergoes a long-range canted antiferromagnetic-type ordering below T1 = 105 K, and a further spin reorientation-type ordering below T2 = 33 K. The low temperature magnetic state of the sample is found to be quite unusual, where a large hysteresis loop is observed in the magnetization curves (coercive field ∼ 33 kOe at 2 K). The isostructural compositions Ho2Al and Er2Al show multiple magnetic transitions: however, they do not show a large hysteresis loop at low temperature. Dy2Al is also associated with an interesting magnetocaloric effect, which is negative and moderate around T1, but becomes large and positive below T2. The observed behavior is related to the large magnetocrystalline anisotropy and narrow domain wall propagation coupled with a field-induced state at low temperature.