Magnetic phase diagram of NdMn 2 (Ge 1− xSi x) 2 system

Abstract

The NdMn 2(Ge 1− x Si x ) 2 system has been studied by means of X-ray powder diffraction and magnetic measurement. With increasing temperature, for the compounds with x<0.6, both a spin reorientation and a ferromagnetic-paramagnetic transition are observed at T r and T C, respectively. The spin reorientation temperature and the Curie temperature decrease with Si content. In compounds with x≥0.4 a transition from ferromagnetic to antiferromagnetic with increasing temperature was observed at a lower temperature T 1, which decreases with increasing Si concentration. A magnetic behaviour similar to that of SmMn 2Ge 2 is observed in compounds with 0.4≤ x<0.6, although a pure antiferromagnetic state is not reached. For compounds with x≥0.6 an antiferromagnetic-paramagnetic transition is observed and the Néel temperature increases monotonically with Si content. A tentative spin phase diagram has been obtained which shows three concentration regions (0≤ x<0.4, 0.4≤ x<0.6, 0.6≤ x≤1.0) of qualitatively different low temperature behavior.