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 Dy_0.5Ho_0.5MnO₃ 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. Dy_0.5Ho_0.5MnO₃ exhibits a clear magnetocrystalline anisotropy with enhanced refrigeration capacity and negative magnetic entropy change along the a-axis. The adiabatic temperature change of Dy_0.5Ho_0.5MnO₃ is 8.5 K, larger than that of HoMnO₃, rendering it a promising choice for low-temperature magnetic refrigeration applications.