Neutron powder diffraction studies and magnetic properties in Nd_(1-x)K_xMnO_3 (x = 0.15 and 0.20) compounds

摘要

Nd_(1-x)K_xMnO_3 (x = 0.15-0.20) compounds were prepared in single phase form and their crystal structure, magnetic structure, and magnetic properties were studied by recording neutron powder diffraction patterns and magnetization measurements down to 22 K. The patterns at low temperatures could be refined by considering magnetic reflections corresponding to ferromagnetic structure. The value of lattice parameters exhibits a sharp fall below FM T_C The temperature variation of magnetization measurements show that both the compounds exhibit paramagnetic to ferromagnetic transition at around 120 K followed by a low temperature spin-glass-like transition at around 45 K. The effective magnetic spin (S_(eff)) toward the double exchange ferromagnetic interaction was determined by analyzing the initial magnetization data in terms of the Brillouin function model. The refined magnetic moments of Mn ion are found to be ferromagnetically aligned along ac plane with a typical value of 2.82(3) μB and 2.68(5) μB per Mn ion for x = 0.15 and x = 0.20 compounds, respectively, at 22 K and their temperature dependence is comparable to the magnetization results.