Magnetic and structural transitions in Dy5Si3Ge

Magnetization and x-ray powder diffraction studies have been performed on a polycrystalline sample of Dy5Si3Ge compound. This compound has a monoclinic crystal structure (Gd5Si2Ge2-type, space group P112(1)/a) at room temperature. Low field magnetization data taken on heating from a zero-field-cooled state indicate a ferromagnetic transition at 62 K (T-C) followed by an antiferromagneticlike cusp at 74 K (T-N). The ferromagnetic transition is marked by a significant hysteresis between zero-field-cooled and field-cooled measurements. Magnetization vs field isotherms display a reversible metamagnetic step with critical fields ranging from similar to 10 k to 55 kOe, in the temperature range of 60-80 K. At 50 K, magnetization is typical of a soft ferromagnet, whereas between 2 and 15 K, the M-H data show a substantial remanence and coercivity. A sharp step in magnetization occurs at 1.8 K in a field of similar to 10 kOe, giving rise to a saturation magnetization (M-s) of similar to 9.7 mu(B)/Dy3+. X-ray diffraction studies in the temperature range of 5-300 K reveal a monoclinic to orthorhombic (Gd5Si4-type, space group Pnma) transition in the neighbourhood of T-C, with a significant thermal hysteresis around the transition. The changes in the lattice parameters, Delta a/a, Delta b/b, and Delta c/c across the transition are similar to-1%, -0.2%, and 0.2%, respectively. The structural transition remains incomplete down to 5 K (with similar to 53 vol % of the monoclinic phase coexisting with similar to 47 vol % of the orthorhombic Gd5Si4-type phase). Application of a magnetic field at 10 K does not lead to the growth of the orthorhombic phase, whereas at 55 K, application of 40 kOe magnetic field increases the concentration of the orthorhombic phase from 24% to 37%.