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This paper presents the design of a transmission-type dual-frequency polarization rotator for linearly polarized electromagnetic wave. The rotator facilitates polarization conversion for incident waves at any azimuth angle ϕ at two specific frequency points, resulting in a transmission wave with a counterclockwise rotation of 2ϕ. The proposed polarization rotator structure comprises three metal layers separated by two dielectric substrates. It includes two large rectangular metal patches positioned orthogonally along the x- and y-axes, respectively, as well as two small rectangular metal patches also positioned orthogonally along the x- and y-axes, respectively. The upper and lower metal layers act as the receiving and radiation ends, respectively. The transmitting and receiving ends are interconnected through coaxial metal holes. Remarkably, polarization conversion efficiencies exceeding 0.95 and 0.94 at 12 and 17 GHz, respectively, are achieved, and these high conversion efficiencies remain consistent as the azimuth angle of incidence changes. Furthermore, experimental results obtained from fabricated samples align well with the simulation ones, thus validating the effectiveness of the proposed polarization rotator. The proposed transmissive dual-frequency polarization rotator exhibits good practical application prospects in mobile satellite communications, GNSS, WLAN, etc.

C6H2KN3O7, monoclinic, P21/m (no. 11), a = 4.1681(2) Å, b = 10.6704(6) Å, c = 10.2381(6) Å, β = 95.134(2)°, V = 453.52(4) Å3, Z = 2, R gt(F) = 0.0404, wR ref(F 2) = 0.0967, T = 295 K.

Controlling spin electromagnetic waves by ultra-thin Pancharatnam-Berry (PB) metasurfaces show promising prospects in the optical and wireless communications. One of the major challenge is to precisely control over the complex wavefronts and spatial power intensity characteristics without relying on massive algorithm optimizations, which requires independent amplitude and phase tuning. However, traditional PB phase can only provide phase control. Here, by introducing the interference of dual geometric phases, we propose a metasurface that can provide arbitrary amplitude and phase manipulations on meta-atom level for spin waves, achieving direct routing of multi-beams with desired intensity distribution. As the experimental demonstration, we design two microwave metasurfaces for respectively controlling the far-field and near-field multi-beam generations with desired spatial scatterings and power allocations, achieving full control of both sophisticated wavefronts and their energy distribution. This approach to directly generate editable spatial beam intensity with tailored wavefront may pave a way to design advanced meta-devices that can be potentially used in many real-world applications, such as multifunctional, multiple-input multiple-output and high-quality imaging devices.

We studied the effect of Eu3+ substitution on the structural, magnetic and magnetocaloric properties of La0.7–xEuxBa0.3MnO3 (x = 0, 0.02, 0.04, 0.06 and 0.08) (LEBMO). The material is prepared by solid-state sintering method. X-ray diffraction and structural refinement parameters indicate that all the synthesized samples have single-phase hexagonal structure. Magnetic measurements indicate that Curie temperature (TC) of the samples decrease with increasing Eu3+ content, because of the weakening of double exchange interaction. All samples present a second-order ferromagnetic to paramagnetic phase transition. Magnetic entropy change (ΔSM) of the samples increases as the Eu3+ content enhance. When x = 0.08, the TC of the sample is 258.6 K and the maximum value of ΔSM reaches 3.27 J kg−1 K−1 at 5 T of a magnetic field. These results indicate that the material can be used as an ideal working material for the normal temperature magnetic refrigeration. [ABSTRACT FROM AUTHOR]

Narrow absorption bandwidth has been a fundamental drawback hindering many metamaterial absorbers for practical applications. In this paper, by loading lumped resistors, we have successfully designed a microwave metamaterial absorber with multioctave wide absorption bandwidth covering the entire X- and Ku-bands, while keeping the thickness of the absorber less than 1/10 of the working wavelength. The polarization-insensitive absorber shows a good angular stability for both transverse electric (TE) and transverse magnetic (TM) incidences. Prototype has been fabricated and measured to validate the design principle and the simulated results, and good agreements are observed between simulated and measured results. The proposed metamaterial absorber offers an efficient way to realize broadband microwave absorption with stable angular performance, which may find potential uses in many applications, for example, electromagnetic compatibility.

The structure, magnetic properties, critical behavior, and magnetocaloric effect (MCE) of La0.7−xEuxBa0.15Ca0.15MnO3 (x = 0, 0.02, 0.04, 0.06, and 0.08) samples have been investigated in the paper. The samples have a rhombohedral crystal structure with the R-3C space group. The magnetic entropy change (− ∆SM) of the samples increases from 2.8 to 3.43 J/kg K (μ0H = 5 T) with increasing Eu3+ content. The Curie temperature (TC) decreases from 228 to 187 K; however, the relative cooling power (RCP) increases from 308 to 340 J/kg due to the weakness of the double-exchange interaction with the Eu3+ content. The samples undergo the second-order magnetic phase transitions with the critical parameters of TC = 191 K, β = 0.849, γ = 1.078, and δ = 2.242. The exponents are close to the mean-field values, which means large disorder of spin magnetic moments in the sample. Our work provides a method to tailor the working temperature of MCE in magnetic refrigeration while maintaining or even increasing the magnetic entropy change. [ABSTRACT FROM AUTHOR]