High Entropy Protected\nSharp Magnetic Transitions\nin Highly Disordered Spinel Ferrites

How disorder affects magnetic ordering is always an intriguing\nquestion, and it becomes even more interesting in the recently rising\nhigh entropy oxides due to the extremely high disorder density. However,\ndue to the lack of high-quality single crystal samples, the strong\ncompositional disorder effect on magnetic transition has not been\ndeeply investigated. In this work, we have successfully synthesized\nhigh-quality single crystalline high entropy spinel ferrites (Mg<sub>0.2</sub>Mn<sub>0.2</sub>Fe<sub>0.2</sub>Co<sub>0.2</sub>Ni<sub>0.2</sub>)<sub><i>x</i></sub>Fe<sub>3‑<i>x</i></sub>O<sub>4</sub>. Our findings from high-temperature magnetization and\nneutron diffraction experiments showed ferrimagnetic transitions at\n748, 694, and 674 K for <i>x</i> values of 1, 1.5, and 1.8,\nrespectively. Notably, the magnetic transition almost showed no broadening\nfor <i>x</i> values of 1 and 1.5, compared to Fe<sub>3</sub>O<sub>4</sub>. Extended X-ray absorption fine structure measurements\nprovided insights into the elemental distribution among the octahedral\nand tetrahedral sites. The random distribution of elements across\nthese sites reduced the formation of local clusters and short-range\norders, enhancing sample homogeneity and preserving the sharpness\nof the magnetic transition, despite bond length variation. Our study\nnot only marks the first successful synthesis of an HEO bulk single\ncrystal exhibiting long-range magnetic order but also sheds light\non the interaction between high configurational entropy and magnetic\norderings. This opens new avenues for future research and applications\nof magnetic high entropy oxides.