Intertwined magnetization and exchange bias reversals across compensation temperature in YbCrO3 compound

Abstract

We have investigated the origin of magnetization and exchange bias (EB) reversals in the YbCrO3 compound at the magnetization compensation temperature, TCOMP of 16.5 K by dc magnetization, ac susceptibility, neutron diffraction (ND), neutron depolarization, specific heat, and dielectric measurements. A weak magnetization (MCr) is observed below the Néel temperature TN (∼120 K) in dc magnetization, which is consistent with a canted antiferromagnetic (AFM) state due to ordering of Cr3+ moments. Specific heat data exhibit a λ-shaped peak at TN. Further, a monotonic increase of ac susceptibility at low temperatures and the Schottky anomaly in the specific heat data account for the polarized nature of the Yb3+ moment (MYb) under the molecular field of the AFM Cr3+ sublattice. Our ND study has confirmed a finite polarized Yb3+ ordered moment, and the Gz-type AFM ordering of Cr3+ moments below TN. The temperature variations of the lattice constants a and b show a crossover from positive to negative thermal expansion (NTE) across the TCOMP while cooling. Below TCOMP, the separation between Cr-Cr atoms lying in the ab plane increases with decrease in temperature, which corroborates with the observed NTE of the lattice constants. In the present compound, the sign change of the net magnetization arising out of the AFM coupled polarized Yb3+ (MYb) and the ferromagnetic Cr3+ (MCr) sublattice moments results in the sign reversal of magnetization. Interestingly, anomalous behavior of the coercive field with its minimum value at T∼TCOMP is observed. EB also changes sign at T∼TCOMP. Moreover, the temperature variation of the real part of the dielectric constant reveals an anomaly at TCOMP, indicating a weak magnetodielectric coupling in the YbCrO3 compound. A training effect analysis ensures the conventional nature of the observed EB. Neutron depolarization study sheds light on the temperature-dependent domain magnetization with its zero value at the TCOMP. The presence of the observed important phenomena viz. magnetization and EB reversals in a single-phase compound suggests their possible use in making magnetization switching, spin-value, thermomagnetic, and other spintronic devices.