STRUCTURAL DETERMINATION AND MAGNETIC-PROPERTIES OF A NEW ORTHORHOMBIC CHROMIUM SELENO STANNATE, CR2SN3SE7

Since the discovery of a monoclinic phase Cr2Sn3Se7, it has been found that, for the same composition, an orthorhombic phase exists. It is d escribed in the Pnma space group with a = 23.097(1) Angstrom, b = 3.83 07(2) Angstrom, and c = 12.5414(6) Angstrom. The structure, refined to a reliability factor R(F) = 2.4%, is built upon [M(6)Se(14)](1)(infin ity) blocks (M = Cr(III) and Sn(IV)) defining 2,4 tunnels occupied by Sn(II) atoms in bicapped trigonal prisms. The orthorhombic Cr2Sn3Se7 s tructure differs from the monoclinic one through the occurrence of [M( 6)Se(14)](1)(infinity) blocks instead of [MSe(2)](2)(infinity), layers . The magnetic susceptibility variation versus the applied magnetic fi eld suggests a spin glass or a superparamagnetism behavior at low temp erature. (C) 1995 Academic Press, Inc.