Ultra-soft ferrimagnetism in a high-entropy spinel oxide driven by site-selective cation disorder.

Abstract

High-entropy materials are complex, multifunctional materials that have reshaped the design of advanced functional materials. Their chemically diverse compositions enable access to a broader compositional space than conventional solid solutions, while simultaneously posing significant challenges for fundamental structure-property understanding. In this study, we introduce a new high-entropy spinel oxide with an exceptionally low coercivity of 1.8 Oe at room temperature, among the lowest reported for bulk spinel oxides, and a high electrical resistivity (1560 ohm cm). Neutron powder diffraction (NPD) and magnetic measurements reveal long-range collinear ferrimagnetic ordering (k = 0, 0, 0) with a transition temperature at 420 K. This rare combination of ultra-soft magnetic behavior, robust ferrimagnetic ordering well above room temperature, and high resistivity highlights its strong potential as an advanced soft-magnetic oxide for low-loss, high-frequency applications. Furthermore, X-ray absorption spectroscopy (XAS), Mössbauer spectroscopy, and NPD analyses were combined to determine the cation distribution and site selectivity across the tetrahedral and octahedral sites of the complex structure.