Metamagnetic phase transition induced large magnetocaloric effect in a Dy0.5Ho0.5MnO3 single crystal.

Abstract

Magnetic refrigeration based on the magnetocaloric effect is gaining interest in orthogonal or hexagonal rare-earth manganite. However, a more comprehensive understanding of the underlying mechanism is still required. We grew a high-quality single crystal of Dy0.5Ho0.5MnO3 using the optical floating zone method, since the parent crystals DyMnO3 and HoMnO3 have orthogonal and hexagonal structures, respectively. The magnetic and magnetocaloric properties and refrigeration mechanisms are thoroughly investigated. Doping modifies the magnetism according to the results obtained from the investigation of magnetic and dielectric properties and heat capacity. The spin reorientation transition shifts towards low temperature in comparison to HoMnO3. Near the Néel temperature of rare-earth sublattices (5 K), the highest changes in negative magnetic entropy under 0-70 kOe are 18 J kg-1 K-1 and 13 J kg-1 K-1 along the a- and c-axes, respectively. The low-temperature metamagnetic phase transition caused by the alterations in the magnetic symmetry of Ho3+ contributes to an increased magnetocaloric effect in comparison to the parent crystals, rendering it a promising choice for magnetic refrigeration applications. Dy0.5Ho0.5MnO3 exhibits a clear magnetocrystalline anisotropy with enhanced refrigeration capacity and negative magnetic entropy change along the a-axis. The adiabatic temperature change of Dy0.5Ho0.5MnO3 is 8.5 K, larger than that of HoMnO3, rendering it a promising choice for low-temperature magnetic refrigeration applications.