Coexistence of positive and negative magnetic entropy changes in CeMn2(Si1 − xGex)2 compounds**Project supported by the Beijing Natural Science Foundation, China (Grant No. 2152034) and the National Natural Science Foundation of China (Grant Nos. 11274357 and 51271196).

Abstract

A series of CeMn2(Si1−xGex)2 (x = 0.2, 0.4, 0.6, 0.8) compounds are prepared by the arc-melting method. All the samples primarily crystallize in the ThCr2Si2-type structure. The temperature dependences of zero-field-cooled (ZFC) and FC magnetization measurements show a transition from antiferromagnetic (AFM) state to ferromagnetic (FM) state at room temperature with the increase of the Ge concentration. For x = 0.4, the sample exhibits two kinds of phase transitions with increasing temperature: from AFM to FM and from FM to paramagnetic (PM) at around TN ∼ 197 K and TC ∼ 300 K, respectively. The corresponding Arrott curves indicate that the AFM–FM transition is of first-order character and the FM–PM transition is of second-order character. Meanwhile, the coexistence of positive and negative magnetic entropy changes can be observed, which are corresponding to the AFM–FM and FM–PM transitions, respectively.