MAGNETIC TRANSITIONS IN ND2NIO4

Five different magnetic phase transitions have been identified and characterized in stoichiometric Nd2NiO4 by means of magnetic-susceptibility and isothermal-magnetization measurements. A collinear antiferromagnetic ordering of Ni2+ magnetic moments exists between T(N1) almost-equal-to 320 K and T(c1) almost-equal-to 130 K where an orthorhombic-to-tetragonal structural phase transition occurs. In this temperature range, Nd3+ ions follow a simple paramagnetic Curie-Weiss-like behavior, while a weak ferromagnetic component appears below 130 K. An internal magnetic field on the Nd3+ ions develops with this structural phase transition. Two additional transitions are observed at T(c2) almost-equal-to 68 K and T(c3) almost-equal-to 45 K which are characterized by a sudden increase of the weak ferromagnetic component. Finally, a peak of the differential susceptibility at T(N2) almost-equal-to 11 K marks a long-range antiferromagnetic ordering of the Nd3+ ions. The internal magnetic field acting on the Nd ions was evaluated to be 5.2 T in the 20 K-T(c2) temperature range.