Complex ferromagnetic state transformation in single crystal [formula omitted

Abstract

The magnetic properties of Nd 0.5 Pb 0.5 MnO 3 single crystal have been studied by dc magnetization and magnetotransport data. The ferromagnetic (FM) to paramagnetic (PM) transition temperature T C and the metal–insulator transition temperature are 177 and 194 K, respectively. The deviation of the inverse susceptibility from the Curie–Weiss law indicates the presence of a Griffiths-like phase in this system, viz., an inverse susceptibility characterized by χ - 1 ∝ ( T - T C Rand ) 1 - λ with λ = 0.81 and T C Rand = 183 K close to the T C 177 K. The slopes of H / M vs. M 2 isotherms are negative between 300 and 194 K and positive above 300 K and below 194 K. The transition cannot be regarded as first or second order on the basis of the Banerjee criterion. The above interesting and complex magnetic transition is a manifestation of competition between the double exchange mechanism and correlations arising from coupled spin and lattice degrees of freedom present in studied system. To analyze the magnetism around T C , the critical behavior of Nd 0.5 Pb 0.5 MnO 3 is investigated based on the data of static magnetization measurements. It is seen that the critical behavior of Nd 0.5 Pb 0.5 MnO 3 belongs to the mean-field model and shows a second-order like magnetic transition at high fields, however, the poor scaling is found toward low fields, which suggest that the critical behavior is related to the observed complicated magnetic transition. The possible origin of observed complex FM state has been discussed based on the competition between the charge/orbital order clusters and the A site disorder.