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 $\mathrm{YbCr}{\mathrm{O}}_{3}$ compound at the magnetization compensation temperature, ${T}_{\mathrm{COMP}}$ of 16.5 K by dc magnetization, ac susceptibility, neutron diffraction (ND), neutron depolarization, specific heat, and dielectric measurements. A weak magnetization $({M}_{\mathrm{Cr}})$ is observed below the N\'eel temperature ${T}_{\mathrm{N}}$ (\ensuremath{\sim}120 K) in dc magnetization, which is consistent with a canted antiferromagnetic (AFM) state due to ordering of ${\mathrm{Cr}}^{3+}$ moments. Specific heat data exhibit a \ensuremath{\lambda}-shaped peak at ${T}_{\mathrm{N}}$. 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 ${\mathrm{Yb}}^{3+}$ moment $({M}_{\mathrm{Yb}})$ under the molecular field of the AFM ${\mathrm{Cr}}^{3+}$ sublattice. Our ND study has confirmed a finite polarized ${\mathrm{Yb}}^{3+}$ ordered moment, and the ${G}_{\mathrm{z}}$-type AFM ordering of ${\mathrm{Cr}}^{3+}$ moments below ${T}_{\mathrm{N}}$. The temperature variations of the lattice constants $a$ and $b$ show a crossover from positive to negative thermal expansion (NTE) across the ${T}_{\mathrm{COMP}}$ while cooling. Below ${T}_{\mathrm{COMP}}$, 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 ${\mathrm{Yb}}^{3+}$ $({M}_{\mathrm{Yb}})$ and the ferromagnetic ${\mathrm{Cr}}^{3+}$ $({M}_{\mathrm{Cr}})$ sublattice moments results in the sign reversal of magnetization. Interestingly, anomalous behavior of the coercive field with its minimum value at $T\ensuremath{\sim}{T}_{\mathrm{COMP}}$ is observed. EB also changes sign at $T\ensuremath{\sim}{T}_{\mathrm{COMP}}$. Moreover, the temperature variation of the real part of the dielectric constant reveals an anomaly at ${T}_{\mathrm{COMP}}$, indicating a weak magnetodielectric coupling in the $\mathrm{YbCr}{\mathrm{O}}_{3}$ 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 ${T}_{\mathrm{COMP}}$. 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.