Magnetic transitions inNd2NiO4

Five different magnetic phase transitions have been identified and characterized in stoichiometric ${\mathrm{Nd}}_2$ ${\mathrm{NiO}}_4$ by means of magnetic-susceptibility and isothermal-magnetization measurements. A collinear antiferromagnetic ordering of ${\mathrm{Ni}}^{2+}$ magnetic moments exists between ${\mathit{T}}_{\mathit{N}1}$≊320 K and ${\mathit{T}}_{\mathit{c}1}$≊130 K where an orthorhombic-to-tetragonal structural phase transition occurs. In this temperature range, ${\mathrm{Nd}}^{3+}$ ions follow a simple paramagnetic Curie-Weiss-like behavior, while a weak ferromagnetic component appears below 130 K. An internal magnetic field on the ${\mathrm{Nd}}^{3+}$ ions develops with this structural phase transition. Two additional transitions are observed at ${\mathit{T}}_{\mathit{c}2}$≊68 K and ${\mathit{T}}_{\mathit{c}3}$≊45 K which are characterized by a sudden increase of the weak ferromagnetic component. Finally, a peak of the differential susceptibility at ${\mathit{T}}_{\mathit{N}2}$≊11 K marks a long-range antiferromagnetic ordering of the ${\mathrm{Nd}}^{3+}$ ions. The internal magnetic field acting on the Nd ions was evaluated to be 5.2 T in the 20 K–${\mathit{T}}_{\mathit{c}2}$ temperature range.