Magnetic phase transition and magnetocaloric effect of DyMn₂Ge₂

We examined magnetocaloric effects of DyMn₂Ge₂, which shows two successive first-order phase transitions at 36 and 40 K. Above 40 K, DyMn₂Ge₂ shows the metamagnetic transition in an appropriate magnetic field and large magnetocaloric effects were observed. The magnetization measurements for single crystals have revealed that the intermediate state appearing between 36 and 40 K in zero field is essentially the same as the high-field phase, which is induced by a magnetic field of 7 T at 4.2 K. Anomalous field dependence of isothermal magnetic entropy change was observed. We discuss the origin of anomalous entropy change as well as that of large magnetocaloric effects in connection with the magnetic structure of DyMn₂Ge₂.