Investigation of the magnetic properties of Mn-doped Jahn–Teller active high entropy rare-earth orthoferrites

Abstract

High-entropy rare-earth orthoferrites with composition (Dy0.2Ho0.2Sm0.2Er0.2Tm0.2)Fe1−xMnxO3 (x = 0.0, 0.25, 0.35), provide an effective platform to investigate entropy-driven tuning of structural distortion and magnetic functionality. Incorporation of Jahn–Teller active Mn-cations induce octahedral distortion, resulting in pronounced modifications to lattice vibrations and magnetic behavior. Raman spectroscopy reveals the appearance of an additional vibrational mode near (∼650 cm−1) in Mn-doped samples, confirming Mn-induced structural distortion. A substantial shift in the spin-reorientation temperature from 96 to 259 K, demonstrating strong sensitivity of magnetic anisotropy to compositional tuning. High-temperature magnetization measurements indicate that the Néel temperature decreases from 632 K with increasing Mn content which is attributed to the weakening of Fe–O–Fe superexchange interactions. Notably, below 10 K, a significant magnetocaloric response is observed compared to many conventional orthoferrite systems. Unlike systems showing first-order phase transitions, the second-order nature of the underlying magnetic phase transition highlights the potential of these high-entropy orthoferrites for the commercial applications related to magnetic refrigeration.