Magnetic and magnetocaloric properties of iron substituted holmium chromite and dysprosium chromite

In this work, HoCrO₃ and Fe substituted HoCrO₃ and DyCrO₃ (i.e. HoCr_0.7Fe_0.3O₃ and DyCr_0.7Fe_0.3O₃) powder samples were synthesized via a solution route. The structural properties of the samples were examined by Raman spectroscopy and X-ray diffraction techniques, which were further confirmed using the first-principle calculations. The dc magnetic measurements indicate that the Cr³⁺ ordering temperatures for the HoCrO₃, HoCr_0.7Fe_0.3O₃, and DyCr_0.7Fe_0.3O₃ samples were 140 K, 174 K, and 160 K, respectively. The ac magnetic measurements not only confirmed the Cr³⁺ ordering transitions in these samples (obtained using dc magnetic measurements), but also clearly showed the Ho³⁺ ordering at ∼10 K in the present HoCrO₃ and HoCr_0.7Fe_0.3O₃ samples, which to our knowledge, is the first ac magnetic evidence of Ho³⁺ ordering in this system. The effective magnetic moments were determined to be 11.67μ_B, 11.30μ_B, and 11.27μ_B for the HoCrO₃, HoCr_0.7Fe_0.3O₃, and DyCr_0.7Fe_0.3O₃ samples, respectively. For the first time, the magnetocaloric properties of HoCrO₃ and HoCr_0.7Fe_0.3O₃ were studied here, showing their potential for applications in magnetic refrigeration. In an applied dc magnetic field of 7 T, the maximum values of magnetic entropy change were determined to be 7.2 (at 20 K), 6.83 (at 20 K), and 13.08 J kg^-1 K^-1 (at 5 K) and the relative cooling power were 408, 387, and 500 J kg^-1 for the HoCrO₃, HoCr_0.7Fe_0.3O₃, and DyCr_0.7Fe_0.3O₃ samples, respectively.