Persistent Structure and Frustrated Magnetism in High Entropy Rare‐Earth Zirconates

Abstract

The configurational complexity and distinct local atomic environments of high entropy oxides remain largely unexplored, leaving structure‐property relationships and the hypothesis that the family offers rich tunability for applications ambiguous. This work investigates the influence of cation size and materials synthesis in determining the resulting structure and magnetic properties of a family of high entropy rare‐earth zirconates (HEREZs, nominal composition RE2Zr2O7 with RE = rare‐earth element combinations including Eu, Gd, Tb, Dy, Ho, La, or Sc). The structural characterization of the series is examined through synchrotron X‐ray diffraction and pair distribution function analysis, and electron microscopy, demonstrating average defect‐fluorite structures with considerable local disorder, in all samples. The surface morphology and particle sizes are found to vary significantly with preparation method, with irregular micron‐sized particles formed by high temperature sintering routes, spherical nanoparticles resulting from chemical co‐precipitation methods, and porous nanoparticle agglomerates resulting from polymer steric entrapment synthesis. In agreement with the disordered cation distribution found across all samples, magnetic measurements indicate that all synthesized HEREZs show frustrated magnetic behavior, as seen in a number of single‐component RE2Zr2O7 pyrochlore oxides. These findings advance the understanding of the local structure of high entropy oxides and demonstrate strategies for designing nanostructured morphologies in the class.

Phase Selectivity and Stability in Compositionally Complex Nano (nA1/n)Co2O4

“…Limited work has been reported on nano-HEOs to date. Wang et al 17 18 Nebulized spray pyrolysis, flame spray pyrolysis, and reverse co-precipitation techniques were employed by Sarkar et al to synthesize nanocrystalline rock salt structure HEOs. 19,20 Lowtemperature solvothermal synthesis with pyrolysis at 400 °C was developed for obtaining nano-spinel structure HEOs by Wang et al, 21 and the sol−gel method was used by Wang et al to fabricate nano-spherical mesoporous spinel HEO particles.…”

“…Wang et al reported a nano-HEO material (Cu–Cr–Fe–Co–Ni–O) obtained via laser scanning ablation. The preparation of nano-fluorite HEO materials with ball-milling, chemical co-precipitation, and polymeric steric entrapment was reported by Jothi et al Nebulized spray pyrolysis, flame spray pyrolysis, and reverse co-precipitation techniques were employed by Sarkar et al to synthesize nanocrystalline rock salt structure HEOs. , Low-temperature solvothermal synthesis with pyrolysis at 400 °C was developed for obtaining nano-spinel structure HEOs by Wang et al., and the sol–gel method was used by Wang et al to fabricate nano-spherical mesoporous spinel HEO particles . We note that materials in these works have been reported as nano-HEOs (not nano-CCOs), though most do not explore/discuss specific thermodynamic criteria distinguishing them one way or the other.…”

Density functional theory study of energetics, local chemical environment and magnetic properties in a high-entropic MnNiSi0.2Ge0.2Sn0.2Al0.2Ga0.2 intermetallic magnet

“…Large variation in local chemical environments have also been shown to lead to useful magnetic properties. For example, compositionally complex alloys, intermetallics, and oxides have been shown to have intriguing magnetic properties [15][16][17][18]. There is significant interest in leveraging these intriguing features to design novel magnets with low coercivity and high saturation magnetization (M s ) [19].…”

Tuneable Short-Range Antiferromagnetic Correlation in Fe-Containing Entropy Stabilized Oxides

“…Although complex magnetic behaviors have been reported in HEOs , such as perovskites, pyrochlores, spinels, zirconates, and Ruddlesden–Popper oxides, so far, only some of them were able to offer magnetic details, such as long-range magnetic order or magnetic phase competition, for example. For a rock salt-type (Co, Cu, Mg, Ni, and Zn)O structure, an antiferromagnetic (AFM) order has been predicted from modeling experiments, which could be confirmed by magnetic susceptibility as well as neutron diffraction below a critical temperature of ∼120 K. , Moreover, the short-range spin ordering in its glassy magnetization state can be tuned by ∼65% by changing the Cu amount from 11 to 27% .…”