The dielectric properties of Z-type hexaferrite Sr3Co2Fe24O41 (SCFO) have been investigated as a function of temperature from 153 to 503 K between 1 and 2 GHz. The dielectric responses of SCFO are found to be frequency dependent and thermally activated. The relaxation-type dielectric behavior is observed to be dominating in the low frequency region and resonance-type dielectric behavior is found to be dominating above 108 Hz. This frequency dependence of dielectric behavior is explained by the damped harmonic oscillator model with temperature dependent coefficients. The imaginary part of impedance (Z″) and modulus (M″) spectra show that there is a distribution of relaxation times. The scaling behaviors of Z″ and M″ spectra further suggest that the distribution of relaxation times is temperature independent at low frequencies. The dielectric loss spectra at different temperatures have not shown a scaling behavior above 108 Hz. A comparison between the Z″ and the M″ spectra indicates that the short-range charges motion dominates at low temperatures and the long-range charges motion dominates at high temperatures. The above results indicate that the dielectric dispersion mechanism in SCFO is temperature independent at low frequencies and temperature dependent at high frequencies due to the domination of resonance behavior.

Epitaxial SrRuO3 (SRO) films with BaTiO3 buffer layer are deposited on mica substrates by pulsed laser deposition. The flexible film layers are subsequently prepared by mechanical exfoliation. The impact of mechanical strain on the magnetic properties of SRO is investigated. To control the applied mechanical strain, the prepared SRO films are firmly attached onto convex molds with different radii of curvature. The magnetization measurements are performed on SRO films under different mechanical strains. It is found that the magnetic properties of SRO films, including Curie temperature, saturated magnetic moment, and coercive field, depend strongly on the mechanical strain. The saturated moment can be enhanced from 1.2 to 3.2 µB per Ru by applying a compressive mechanical strain, which is presumably attributed to a spin state transition. The magnetic anisotropy can be varied as well by exerting mechanical compressive or tensile strain. The flexible SRO films on mica substrate with highly tunable magnetic properties show a great potential for novel applications in flexible electronics.

Magnetoelectric materials which simultaneously exhibit electric polarization and magnetism have attracted more and more attention due to their novel physical properties and promising applications for next-generation devices. Exploring new materials with outstanding magnetoelectric performance, especially the manipulation of magnetization by electric field, is of great importance. Here, we demonstrate the cross-coupling between magnetic and electric orders in polycrystalline Co4Nb2O9, in which not only magnetic-field-induced electric polarization but also electric field control of magnetism is observed. These results reveal rich physical phenomenon and potential applications in this compound.

Stimuli‐responsive smart optical materials hold great promise for applications in active optics, display, sensing, energy conversion, military camouflage, and artificial intelligence. However, their applications are greatly restricted by the difficulty of tuning different optical properties within the same material, especially by a single stimulus. Here, magnetic modulations of multiple optical properties are demonstrated in a crystalline colloidal array (CCA) of magnetic nanorods. Small‐angle X‐ray scattering studies reveal that these nanorods form an unusual monoclinic crystal in concentrated suspensions. The CCA exhibits optical anisotropy in the form of a photonic bandgap and birefringence, thus enabling magnetic tuning of the structural color and transmittance at a rate of 50 Hz. As a proof‐of‐concept, it is further demonstrated that the fabrication of a multifunctional device for display, anticounterfeiting, and smart‐window applications based on this multiple magneto‐optical effect. The study not only provides a new model system for understanding colloidal assembly, but also opens up opportunities for new applications of smart optical materials for various purposes.

Inconceivably large changes (up to 10 6 %) of the resistivity induced by external magnetic field-a phenomenon known as the extreme magnetoresistance effect has been reported in a great number of exotic semimetals. The very recent and exciting discoveries mainly pay attention to the compounds without magnetic ground states, which appears to limit the potential growth of semimetal family. For fundamental scientific interests, introduction of spin degree of freedom would provide an almost ideal platform for investigating the correlation effect between magnetism, crystallographic structure and electric resistivity in materials. Here, we report the experimental observation of metamagnetic behaviors and transport properties of HoBi single crystals. Being a magnetic member of the rare earth monopnictide family, the magnetoresistance of HoBi is significantly modulated by the magnetic orders at low temperature, which shows a nonmonotonic increment across the successive magnetic phases and reaches 10 4 % (9 T and 2 K) in the ferromagnetic state. Kohler's rule predicts that more than one type of carriers dominates the transport properties. Well fitted magnetoresistance and Hall resistivity curves by the semiclassical two-band model suggest that the densities of electron and hole carriers are nearly compensated and the carrier mobilities in this compound are ultrahigh. Besides, the inverted band structures and nonzero Z 2 topological invariant indicate that possible nontrivial electronic states could generate in the ferromagnetic phase of HoBi. Combining the experimental and theoretical results, it is found that the cooperative action of carrier compensation effect and ultrahigh mobility might contribute to the extreme magnetoresistance observed in the titled compound. These findings suggest a paradigm for obtaining the extreme magnetoresistance in magnetic compounds and are relevant to understand the rare-earth-based correlated topological materials. tunnel magnetoresistance [2-5], extremely large magnetoresistance have attracted increasing interest [6, 7], since it not only offer the potential to design new devices, but also pose challenges to understand the fundamental phenomena in nature. The extreme magnetoresistance has been widely reported in the classic elemental semimetal Bi, topological semimetals WTe 2 , Cd 3 As 2 , TaPn (Pn = As, Sb) family, pyrite-type PtBi 2 , RPtBi (R=Nd, Gd), RPn (R=rare earth; Pn = Sb, Bi) and so on . Ever since the unprecedentedly large magnetoresistance is revealed in LaSb, the research enthusiasm on rare earth monopnictides RPn (R=rare earth, Pn = Sb, Bi) is inspired [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. The family has been widely studied in the 1980-90s for its heavy-fermion nature [31]. Intriguingly, the recent calculations predict that LaPn (Pn = N, P, As, Sb, and Bi) could be a topological prototype material with band inversion at X point of the bulk fcc Brillouin zone [32]. Afterwards, further investigation on this family has been systematically performe...

We report the gram-scale hydrothermal synthesis of superparamagnetic FeO CNCs with superior long-term charge stability, which are suitable building blocks for magnetically responsive photonic crystals (MRPCs) with widely, rapidly and reversibly tunable diffractions across the visible and near IR range, as well as long-term stability of photonic performances. The scalable synthesis of FeO CNCs with excellent long-term colloidal stability will facilitate their wide application in photonics, biomedicine, catalysis and other areas.

Self‐assembled nanocomposite films and coatings have huge potential for many functional and structural applications. However, control and manipulation of the nanostructures is still at very early stage. Here, guidelines are established for manipulating the types of composite structures that can be achieved. In order to do this, a well studied (YBa2Cu3O7‐δ)1‐x:(BaZrO3)x ‘model’ system is used. A switch from BaZrO3 nanorods in YBa2Cu3O7‐δ matrix to planar, horizontal layered plates is found with increasing x, with a transitional cross‐ply structure forming between these states at x = 0.4. The switch is related to a release in strain energy which builds up in the YBa2Cu3O7‐δ with increasing x. At x = 0.5, an unusually low strain state is observed in the planar composite structure, which is postulated to arise from a pseudo‐spinodal mechanism.

Nanoellipsoid-based photonic crystal supraparticles with tailored shapes and unusual internal structures are developed.