High‐entropy (HE) oxides have become increasingly popular as electromagnetic wave‐absorbing materials owing to their customizable structure and unique HE effects. However, the weak loss property of single‐phase HE ceramics and the approaches implemented to improve them based on semi‐empirical rules severely limit their development. Herein, two biphasic HE oxides are prepared by simple sintering to realize accurate regulation of crystal phases and structural defects. It is verified that HE effects cause various defects that are beneficial for microwave dissipation within complex‐phase ceramics. In spinel/perovskite HE oxides, around the interface of spinel (111) and perovskite (110) planes, notable stress concentrations and lattice distortions are directly observed, inducing numerous point defects and stacking faults. Interestingly, besides the existing heterogeneous interface of rock salt (220)/spinel (220) plane and defects, rock salt/spinel HE oxides enabled synergistic effects via the precise regulation of components’ phase. Driven by structural defects and multi‐phases in HE complexes, the intense polarization is evidently found, confirmed by the first‐principles calculations. Accordingly, the two complex‐phase HE oxides demonstrate excellent microwave absorption performance, and the minimal reflection loss of −54.5 dB is achieved. Therefore, this study provides valuable guidelines for the design of microwave absorbers using HE oxides.

Exchange bias was observed in the Ni50Mn36Sn14 Heusler alloy after field cooling by means of hysteresis loop measurement. The hysteresis loops shift along the axis of an applied field and its magnitude significantly increased with decreasing temperature below 70K. This effect could be understood as a result of exchange anisotropy created at the interface between an antiferromagnet and a ferromagnet in the phase separated of martensitic state. Above 70K, however, the exchange bias field disappeared and the coercivity significantly reduced owing to the fact that the pinning between an antiferromagnet and a ferromagnet becomes weaker with increasing temperature.

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The prospect of controlling the magnetization (M) of a material is of great importance from the viewpoints of fundamental physics and future applications of emerging spintronics. A class of rare-earth orthoferrites RFeO3 (R is rare-earth element) materials exhibit striking physical properties of spin switching and magnetization reversal induced by temperature and/or applied magnetic field. Furthermore, due to the novel magnetic, magneto-optic and multiferroic properties etc., RFeO3 materials are attracting more and more interests in recent years. We have prepared and investigated a prototype of RFeO3 materials, namely SmFeO3 single-crystal. And we report magnetic measurements upon both field cooling (FC) and zero-field cooling (ZFC) of the sample, as a function of temperature and applied magnetic field. The central findings of this study include that the magnetization of single-crystal SmFeO3 can be switched by temperature, and tuning the magnitude of applied magnetic field allows us to realize such spin switching even at room temperature.

The addition of numerous main metal elements into highentropy alloys (HEAs) have been popular since their discovery in 2004. [2] This has provided a vast combinatorial space for the exploration of new materials with unexplored abnormal functionalities. In general, four core factors, namely, sluggish diffusion, configurational entropy, lattice distortion, and cocktail effects, affect the crystal structure and properties of HEAs. [3] Since 2015, the concept of high entropy has been successfully expanded to include oxides. [4] Similar to HEAs, high-entropy oxides (HEOs) are defined as compositions consisting of oxygen and more than five metal cations in equimolar or near equimolar ratios in the range of 5-35% atomic concentration. [5] HEOs are rapidly emerging as delicate functional constituents that offer excellent compositional flexibility that permits the stabilization of numerous compositions with various crystal structures (e.g., rock-salt, spinel, fluorite, perovskite, and pyrochlore phases). [6] Consequently, HEOs present numerous attractive functional properties, such as high ionic conductivity; [7] superior storage capacity retention and good stable cycles of Li battery; [8] low thermal conductivity and good thermal stability; colossal dielectric constant; [9] and novel magnetic phenomena. [10] However, a deep understanding of their microstructures has yet to emerge. Thus, it is extremely urgent to learn more about the microstructure of HEOs to further understand their anomalous High-entropy oxides (HEOs), which incorporate multiple-principal cations into single-phase crystals and interact with diverse metal ions, extend the border for available compositions and unprecedented properties. Herein, a high-entropy-stabilized (Ca 0.2 Sr 0.2 Ba 0.2 La 0.2 Pb 0.2 )TiO 3 perovskite is reported, and the effective absorption bandwidth (90% absorption) improves almost two times than that of BaTiO 3 . The results demonstrate that the regulation of entropy configuration can yield significant grain boundaries, oxygen defects, and an ultradense distorted lattice. These characteristics give rise to strong interfacial and defect-induced polarizations, thus synergistically contributing to the dielectric attenuation performance. Moreover, the large strains derived from the strong lattice distortions in the high-entropy perovskite offer varied transport for electron carriers. The high-entropy-enhanced positive/negative charges accumulation around grain boundaries and strain-concentrated location, quantitatively validated by electron holography, results in unusual dielectric polarization loss. This study opens up an effective avenue for designing strong microwave absorption materials to satisfy the increasingly demanding requirements of advanced and integrated electronics. This work also offers a paradigm for improving other interesting properties for HEOs through entropy engineering.

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The rational design of magnetic composites has great potential for electromagnetic (EM) absorption, particularly in the low-frequency range of 2-8 GHz. However, the scalable synthesis of such magnetic absorbers with both high magnetic content and good dispersity remains challenging. In this study, a confined diffusion strategy is proposed to fabricate functional magneticcarbon hollow microspheres. Driven by the ferromagnetic enhanced Kirkendall diffusion effect, the in situ alloying of FeCo nanoparticles is tightly confined in carbon shells, effectively inhibiting magnetic agglomeration. Moreover, the core-shell FeCo-carbon nano-units further assemble into dispersive microscale magnetic-carbon Janus bulges on both the inner and outer surfaces of the hollow microsphere. The optimized hollow FeCo@C microspheres exhibit excellent low-frequency EM wave absorption performance: the minimum reflection loss (RL min ) is −35.9 dB, and the absorption bandwidth covers almost the entire C-band. Systematic investigation reveals that the large size of the magnetic-carbon integration, high-density confined magnetic units, and strong magnetic coupling are essential for enhancing the magnetic loss dissipation of low-frequency EM waves. This study provides a novel strategy for fabricating advanced EM wave absorbers and significant inspiration for investigating the magnetic attenuation mechanism at low frequency.

Positive exchange bias from magnetization reversal in La1xPrxCrO3 (x 0.7-0.85) Appl.