Nature of magnetism and magnetic-field-induced transitions in non-collinear antiferromagnet Er2O3

The nature of magnetism in Er2O3 is investigated by detailed studies of the temperature (2-300 K) and magnetic field (up to 90 kOe) dependence of the magnetization M of powder sample of Er2O3. The results show paramagnetic to antiferromagnetic (AFM) transition occurring at TN=3.3 K. For T>TN the magnetic susceptibility vs. temperature data follows the Curie-Weiss (χ=C/(T−θ)) variation with θ=−10.2 K and magnetic moment μ=6.68μB/Er3+ ion determined from C. Molecular field model is used to determine the nn (nnn) exchange constants J1(J2)=−0.57 K (−3.38 K). The M vs. H data at 2 K analyzed in terms of dM/dH vs. H variations show two field-induced transitions, the first one at HSF≃15kOe and the second one at HS≃31kOe. Arguments and analysis are presented to show that HSF represents the spin-flop transition whereas for H>HS, the system is field-aligned ferromagnetically since the calculated value of HS for ferromagnetic ordering using the above magnitudes of J1 and J2 agrees well with the experimental HS. The temperature dependence of HSF is shown to follow the normalized Brillouin function variation for spin S=1/2 valid for Er2O3. The magnetic field dependence of TN is measured and shown to follow the equation: TN(H)=TN(0)−D1H2, expected for antiferromagnets.