Magnetic and magnetocaloric properties of HoCrO3 and HoCr0.5Al0.5O3: Experimental and DFT study

Abstract

The impact of Al3+, a non-magnetic element, replacing Cr3+ in the HoCrO3 perovskite on its crystal structure, magnetic characteristics, and magnetocaloric behavior has been reported. X-ray diffraction (XRD) analysis revealed octahedral distortions and changes in lattice parameters upon incorporating Al3+ ions. Magnetic studies showed that undoped and doped samples transition from a paramagnetic state to a canted antiferromagnetic state below the critical Néel temperature (TN), associated with Cr3+-O2--Cr3+ exchange interactions. Al3+ doping in HoCrO3 lowered the TN value because the substitution reduced the number of magnetic Cr3+ ions, diluting the magnetic sub-lattice and weakening overall magnetic interactions. Density functional theory (DFT) studies confirmed that Al3+ doping altered the magnetic configurations from AFM-G to AFM-C. The energy difference |EAFM-G – EAFM-C| for HoCrO3 was significantly higher (52 meV) than that observed for HoCr0.5Al0.5O3 (13.8 meV), indicating greater stability in the doped compound. From an application standpoint, Al3+ doping reduced coercivity and enhanced the compound's magnetocaloric effect. Specifically, the Al3+-doped HoCr0.5Al0.5O3 exhibited a change in magnetic entropy, -ΔSm ∼8.83 Jkg−1K−1 at a 5T applied field, 36 % higher than HoCrO₃ compound (-ΔSm ∼ 6.47 Jkg−1K−1 at 5T) under the same conditions. This enhancement of -ΔSm positions the Al3+-doped HoCr0.5Al0.5O3 as a promising material for magnetic refrigeration applications.

Publication Title

Ceramics International

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