Structure dependence of magnetic properties of Nd5Si4−xGex (<f>x=1.2</f> and 2)

The crystal structure and magnetic properties of ternary compounds <f>Nd5Si4−xGex</f> (<f>x=1.2</f> and 2) were investigated by means of X-ray powder diffraction and magnetic measurements. The as-cast samples <f>α</f>-Nd5Si2.8Ge1.2 and <f>α</f>-Nd5Si2Ge2 crystallize in the orthorhombic Gd5Si4-type structure with space group Pnma and the monoclinic Gd5Si2Ge2-type structure with space group <f>P1121/a</f>, respectively. The samples <f>β</f>-Nd5Si2.8Ge1.2 and <f>β</f>-Nd5Si2Ge2 annealed at 1273 K all crystallize in the tetragonal <f>Zr5Si4</f>-type structure with space group <f>P41212</f>. All phases of <f>α</f>-Nd5Si2.8Ge1.2, <f>β</f>-Nd5Si2.8Ge1.2, <f>α</f>-Nd5Si2Ge2 and <f>β</f>-Nd5Si2Ge2 exhibit a spin glasslike behavior and may have a canted magnetic structure. The Curie temperature shows a strong dependence on the crystal structure of the compounds. The average interatomic distances of magnetic Nd atoms and the amount of the covalent (Si,Ge)–(Si,Ge) bond pairs in these phases are different, which may be responsible for their different magnetic properties. [Copyright &y& Elsevier]