Negative magnetic moment induced by a magnetic field in the region of the magnetic phase transition in SmMnSi compound

The magnetic, electrical and crystallographic properties of SmMnSi compound with CeFeSi-type structure have been studied by magnetization, susceptibil ity, conductivity and thermal expansion measurements. The unusual magnetic behaviour with two magnetic phase transitions at T-r = 130 K and T-N = 240 K and the compensation point T-c 215 K have been observed. A large temperat ure hysteresis takes place around T-c. The results are compared with those obtained for isostructural RMnSi compounds and discussed assuming the stron g correlation of exchange interactions with interatomic distance.