Anisotropic magnetic properties and giant magnetocaloric effect in antiferromagnetic $R$MnO${}_3$ crystals ($R$=Dy, Tb, Ho and Yb)

Abstract

We have systematically investigated the magnetic properties and magnetocaloric effect (MCE) in $R$MnO${}_3$ ($R$$=$Dy, Tb, Ho and Yb) single crystals. Above a critical value of applied field ($H_c$), $R$MnO${}_3$ undergo a first-order antiferromagnetic (AFM) to ferromagnetic (FM) transition below the ordering temperature ($T_N^R$) of $R^{3+}$ moment and a second-order FM to paramagnetic (PM) transition above $T_N^R$. Both $H$ and $T$ dependence of $M$ shows that the system is highly anisotropic in the FM as well as PM states and, as a result, the magnetic entropy change ($\Delta S_M$) is extremely sensitive to the direction of applied field and can be negative (normal MCE) or positive (inverse MCE). For hexagonal HoMnO${}_3$ and YbMnO${}_3$ systems, a very small inverse MCE is observed only for $H$ parallel to c axis and it decreases with increasing $H$ and crosses over to normal one above $H_c$. On the other hand, for orthorhombic DyMnO${}_3$ and TbMnO${}_3$, though the inverse MCE disappears above $H_c$ along easy-axis of magnetization, it increases rapidly with $H$ along hard-axis of magnetization for $T$$\ll$$T_N^R$. Except for YbMnO${}_3$, the values of $\Delta S_M$, relative cooling power and adiabatic temperature change along easy-axis of magnetization are quite large in the field-induced FM state for a moderate field strength. The large values of these parameters, together with negligible hysteresis, suggest that the multiferroic manganites could be potential materials for magnetic refrigeration in the low-temperature region.

10 pages, 11 figures

References in corpus (4)

• Neutron diffraction study of TbMnO3: Magnetic structure revisited
• Enhanced ferroelectric polarization by induced Dy spin-order in multiferroic DyMnO3
• Commensurate Dy magnetic ordering associated with incommensurate lattice distortion in orthorhombic DyMnO3
• Magnetic-field induced effects on the electric polarization in RMnO3 (R = Dy, Gd)

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