Hydrogen induced structural and magnetic transformation in the SmMn2H2 compound

X-Ray and magnetic investigations of the SmMn2H2 hydride at temperatures ra nging from room temperature down to liquid nitrogen temperature are present ed and analysed. It has been shown that hydrogen increases the magnetic ord ering temperature from 86 K for SmMn2, to about 248 K for SmMn2H2, which is accompanied by a structural transformation. SmMn2, having the hexagonal C1 4 structure, is distorted into orthorombic below 86 K. However, for SmMn2H2 having also the same C14 structure, we observed the transformation of the hexagonal phase into two separate hexagonal phases below 248 K. In contrast to the parent antiferromagnetic SmMn2 compound, a small ferromagnetic comp onent is observed in the hydride. (C) 1999 Elsevier Science Ltd. All rights reserved.