Room temperature large magnetodielectric and magnetoimpedance in (NiMnFeAlZn)3O4 high entropy oxide

Abstract

Spinel-structured high entropy oxide (HEO) establishes a unique class of multifunctional materials, where intrinsic chemical disorder and multi-site tenancy enable a unique interplay between spin and charge dynamics. In this work, we report the interplay between magnetic field and dielectric and impedance behaviors in such a chemically complex HEO. For this purpose, a spinel-structured (NiMnFeAlZn)3O4 single-phase compound was synthesized via the solid-state method, its microstructure was analyzed at the atomic level, and its electronic, magnetic, dielectric, and impedance properties were systematically characterized. The detailed atomic-level microstructure and electronic properties analyses revealed a strong site presence by Zn2+ and Al3+ in tetrahedral and octahedral sublattices, respectively, while Ni, Mn, and Fe cations with mixed-valence state are distributed across both sublattices. Thermomagnetization studies and detailed analyses of magnetic data using the modified Arrott plot method and the modified Curie–Weiss law revealed a ferrimagnetic-to-paramagnetic phase transition around 217 K. The dielectric and impedance studies showed a strong temperature- and frequency-dependent behavior, underscoring the intrinsic association between spin and charge dynamics. As a result, a notably large room-temperature magnetodielectric (MD) effect (10.3%) and magnetoimpedance (MZ) response (−13%) were observed at 2.2T. Comparative analysis of the square of normalized magnetization with normalized MD and MZ, along with the field-dependent thermomagnetization, not only confirmed that these enhanced functionalities stem from the field-induced magnetic ordering but also highlighted the importance of harnessing the couplings in these spinel-based HEOs for applications in next-generation electromagnetic, memory, sensing, and spintronic applications.