Structural, magnetic and x-ray absorption spectroscopy studies of new Cr-based low, medium and high-entropy spinel oxides

Abstract: The emergence of high-entropy oxides has spurred significant research interest in recent times. These compounds exhibit exotic functional properties that often transcend simple linear combinations of their constituent elements. Herein, we present a new series of Cr-based low, medium, and high entropy spinel oxides with composition NiCr2O4, [Ni0.5Mn0.5]Cr2O4, [Ni0.33Mn0.33Co0.33]Cr2O4, [Ni0.25Mn0.25Co0.25Cu0.25]Cr2O4, [Ni0.2Mn0.2Co0.2Cu0.2Zn0.2]Cr2O4, and [Ni0.2Mg0.2Co0.2Cu0.2Zn0.2]Cr2O4. We conducted detailed structural (X-ray and Neutron diffraction), microstructural, Raman spectroscopy, magnetic, and X-ray absorption spectroscopy measurements on these materials. Our study reveals that the incorporation of multiple cations at the A-site of the structure (AB2O4) significantly modulates the magnetic properties. These compounds exhibit transitions from complex ferrimagnetic ([Ni0.2Mn0.2Co0.2Cu0.2Zn0.2]Cr2O4) to antiferromagnetic ([Ni0.2Mg0.2Co0.2Cu0.2Zn0.2]Cr2O4) states, with remarkable coercivity variations, demonstrating the ability to tailor magnetic responses through compositional design.