The intermetallic compound ${\mathrm{SmMn}}_2{\mathrm{Ge}}_2,$ displaying multiple magnetic phase transitions, is investigated in detail for its magnetization behavior near the 145-K first-order ferromagnetic-to-antiferromagnetic transition occuring on cooling, in particular, for thermomagnetic history effects in the magnetization data. The most unusual finding is that the thermomagnetic irreversibility, $\left[{=M}^{\mathrm{FCW}}\mathrm{}\right(T\left)\mathrm{}-M^{\mathrm{ZFC}}\mathrm{}\right(T\left)\mathrm{}\right]$ at 135 K is higher in intermediate magnetic-field strengths. By studying the response of the sample (i.e., thermomagnetic irreversibility and thermal hysteresis) to different histories of application of magnetic field and temperature, we demonstrate how the supercooling and superheating of the metastable magnetic phases across the first-order transition at 145 K contribute to overall thermomagnetic irreversibility.

• Received 19 March 2002

DOI:https://doi.org/10.1103/PhysRevB.66.014424