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A simple design of a triple-band multi-polarization reflective polarization converter is presented. The proposed device consists of a modified split-ring structure and a cut-wire resonator. A linearly polarized (LP) incident electromagnetic (EM) wave can be reflected into an orthogonally directed LP wave in two widebands and a circularly polarized (CP) wave in one wideband. The triple-band multi-polarization conversion performance is achieved by combing multiple plasmon resonances, which can be controlled by adjusting the parameters of the modified split-ring structure and the cut-wire resonator independently. The simulations show that a y/x-polarized incident EM wave can be rotated to an x/y-polarized reflected wave from 5.75–9.40 GHz (a fractional bandwidth of 48.18%) and 14.22–16.28 GHz (a fractional bandwidth of 13.51%) with a polarization conversion ratio over 0.9. Besides, a CP reflection is obtained from 10.58–13.88 GHz (a fractional bandwidth of 26.98%) with an axial ratio of less than 3 dB. The device is prototyped and a good agreement between experimental and simulated results is obtained. The proposed multi-functional polarization converter yields a wideband in each polarization conversion band and can be extended to work in other frequency bands.

Calculated in this paper are the band structures of both the one-dimensional (1D) antiferromagnet Sr2CuO3 and the two-dimensional one Sr2CuO2Cl2 by using the local-spin-density approximation (LSDA) and the on-site Coulomb interaction U correction (LSDA+U). The pd hybridization is weaker in 1D Sr2CuO3 than in 2D Sr2CuO2Cl2, thus favoring a spin-polarized and insulating solution for the former but a nonmagnetic and metallic state for the latter. While the strong d–d electron correlations are responsible for the O 2p-Cu 3d charge-transfer insulating character of these two cuprates. The calculated band gaps and spin moments are well comparable with the experimental and theoretical values.

The fully self‐consistent discrete variational method within the local‐spin‐density framework has been employed to obtain the electronic structure and magnetic moments of the Mn‐containing cubic Laves phase pseudobinary compound of YFe2. The calculated results show that the substitution of Mn atoms on Fe sites weakens the ferromagnetism of this compound. The magnetic moments on distinct atomic sites were derived from the calculation. We found that when the Fe atom has one Mn atom in its nearest neighbor sites, its magnetic moment decreases rapidly, while the Mn moment is 0.71μB, parallel to the Fe moment. Based upon our results, the various experimental data have been satisfactorily explained.

The electronic structure and magnetic properties of rare‐earth iron compounds R2Fe17Nx (x=0,3,4) and R2Fe17Cx (x=0,3) (R=Sm,Nd) have been studied by the self‐consistent, spin‐polarized local spin density functional theory calculations. Several cluster models were used to study the electronic structure of these compounds. For the R2Fe17Nx and R2Fe17Cx (x=0,3), the 9(e) sites in a unit cell are considered as occupied by N or C atoms. The additional N atom in the x=4 case is considered as occupying the 3(b) sites. The distribution of electrons and the magnetic moments for four kinds of crystalline inequivalent Fe atoms, Sm (Nd) and N(C) are calculated. The role of N or C atom in above compounds were discussed.

The textured Pr2Fe14B nanoflakes were produced by surfactant-assisted ball milling (SABM). Single phase tetragonal structure was characterized for the samples before and after SABM by X-ray diffraction (XRD). The thickness and length of the as-milled flakes are mainly in the range of 50–150 nm and 0.5–2 μm, respectively. For the field-aligned Pr2Fe14B nanoflakes, the out-of-plane texture (the easy magnetization direction (EMD) along the c-axis) is indicated from the increasing (00l) peaks in the XRD patterns. SEM image demonstrates that the EMD is parallel to flaky surface, which is different from the RCo5 (R = rare earth) system with EMD perpendicular to the surface. We propose a hypothesis that the easy glide planes are related with the area of crystal planes. In addition, a large coercivity Hc = 3.9 kOe is observed in the Pr2Fe14B flakes with strong texture.

The microstructure, crystal structure, and magnetic properties of low-temperature phase (LTP) Mn-Bi nanosheets, prepared by surfactant assistant high-energy ball milling (SA-HEBM) with oleylamine and oleic acid as the surfactant, were examined with scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometer, respectively. Effect of ball-milling time on the coercivity of LTP Mn-Bi nanosheets was systematically investigated. Results show that the high energy ball milling time from tens of minutes to several hours results in the coercivity increase of Mn-Bi powders and peak values of 14.3 kOe around 10 h. LTP Mn-Bi nanosheets are characterized by an average thickness of tens of nanometers, an average diameter of ∼1.5 μm, and possess a relatively large aspect ratio, an ultra-high room temperature coercivity of 22.3 kOe, a significant geometrical and magnetic anisotropy, and a strong (00l) crystal texture. Magnetization and demagnetization behaviors reveal that wall pinning is the dominant coercivity mechanism in these LTP Mn-Bi nanosheets. The ultrafine grain refinement introduced by the SA-HEBM process contribute to the ultra-high coercivity of LTP Mn-Bi nanosheets and a large number of defects put a powerful pinning effect on the magnetic domain movement, simultaneously. Further magnetic measurement at 437 K shows that a high coercivity of 17.8 kOe and a strong positive temperature coefficient of coercivity existed in the bonded permanent magnet made by LTP Mn-Bi nanosheets.

The effect of the milling time on the structure, morphology, coercivity, and remanence ratio of textured PrCo5 nanoflakes produced by low power surfactant-assisted ball milling (SABM) was investigated. The X-ray powder diffraction (XRD) patterns indicate that the SABM PrCo5 samples are all CaCu5-type hexagonal structure. The average grain size is smaller than 10 nm when the SABM time is equal to or longer than 5.5 h. The thickness of nanoflakes is mainly in the range of 50−100 nm while the length is 0.5−5 μm when the SABM time reaches 8 h. For the field-aligned PrCo5 nanoflakes, the out-of-plane texture is indicated from the increasing (0 0 l) peaks in the XRD patterns, and the easy magnetization direction is perpendicular to the flake surface. The strong texture of PrCo5 nanoflakes leads to a large coercivity Hc (7.8 kOe) and obvious anisotropic magnetic behaviors for the aligned samples.

The magnetic and magnetocaloric properties of TmNi1-xCuxAl (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) compounds have been investigated. With the substitution of Ni by Cu, the Tm-magnetic moment rotates its direction from basal plane to the c-axis and finally becomes canted antiferromagnetism structure with larger projected moments along the c-axis near Tord. Furthermore, large reversible magnetocaloric effects have been observed in TmNi1-xCuxAl compounds around Tord, with no thermal hysteresis and magnetic hysteresis loss. The values of −ΔSMmax and refrigerant capacity are greatly improved when the part of Ni was superseded by Cu. In particular, under the magnetic field change of 2 T, a large −ΔSMmax of TmNi0.7Cu0.3Al (10.7 J/kg K) is almost twice that of TmNiAl (5.5 J/kg K) and 17.2 J/kg K for TmCuAl around 4 K. The present results indicate that TmNi1-xCuxAl (x ≥ 0.3) compounds could be considered as good candidate materials for low-temperature and low-field magnetic refrigerant.

By micromagnetic simulation, we investigated the interaction between propagating spin wave (or magnonic) and a 360° domain wall in a nanostrip. It is found that propagating spin wave can drive a 360° domain wall motion, and the velocity and direction are closely related to the transmission coefficient of the spin wave of the domain wall. When the spin wave passes through the domain wall completely, the 360° domain wall moves toward the spin wave source. When the spin wave is reflected by the domain wall, the 360° domain wall moves along the spin wave propagation direction. Moreover, when the frequency of the spin wave is coincident with that of the 360° domain wall normal mode, the 360° domain wall velocity will be resonantly enhanced no matter which direction the 360 DW moves along. On the other hand, when the spin wave is reflected from the moving 360° domain wall, we observed the Doppler effect clearly. After passing through a 360° domain wall, the phase of the spin wave is changed, and the phase shift is related to the frequency. Nevertheless, phase shift could be manipulated by the number of 360° domain walls that spin wave passing through.

An improvement is made on our previous band results of Sr2CuO3 and Sr2CuO2Cl2 by including the extended Sr 4p valence orbital in the present self-consistent calculations. The differences between our improved results and those of others are mainly due to different evaluation of the ionicity in these compounds.

We present the study of the giant magnetoresistance effect in ferromagnetically ordered thin film and bulk based on the Hund’s rule coupling between the mobile d electron and the core spin of Mn ions. It has been shown that the resistivity is proportional to the spin–spin correlation functions, a maximum resistivity appears near the critical point in absence of magnetic field and an applied field drives the resistivity peak to higher temperature and reduces the peak value, which is in agreement with the experiments. The giant magnetoresistance effect in thin film is attributed to the spin‐correlation‐dependent scattering and the low‐dimensional character.