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Abstract-dynamic plasma sheath can severely interfere with the communication of hypersonic vehicles during atmospheric reentry. Theoretical and experimental results show that low-frequency (LF) electromagnetic (EM) waves could penetrate the plasma sheath, building a feasible method to solve the "radio blackout" problem. This paper discovers that the propagation of LF EM waves in plasmas is still influenced by parasitic modulation effects. Compared to microwave frequencies, the impact of parasitic modulation effects on signal modulation patterns is more distinct for LF EM waves. In contrast to the microwave frequency range, where the rotation direction of QPSK signal constellation points changes with the ratio of plasma frequency to electromagnetic wave frequency, in the LF range, the constellation points undergo limited clockwise rotation. This phenomenon can be attributed to the unique magnetic field propagation mechanism of LF EM waves in dynamic plasmas. This paper analyzes the mechanism of this specific parasitic modulation effect and discovers a sinusoidal transformation relationship between amplitude attenuation and phase shift. Meanwhile, the experimental and simulation results proved that the time-varying plasma could cause the parasitic modulation effect of LF EM wave, resulting in a limited clockwise rotation of orthogonal phase-shift keying constellation points, which is consistent with the theoretical analysis. [ABSTRACT FROM AUTHOR]

Antiferromagnets with the intrinsic advantages of terahertz spin dynamics and negligible stray fields have been extensively studied for spintronic applications. In particular, spintronic research on antiferromagnets has expanded its focus from collinear to noncollinear Weyl antiferromagnets and discovered that Mn3X (X = Sn, Ge) produces substantial magneto-electric responses. Therefore, noncollinear antiferromagnets could be an ideal spintronic platform. Exploring the domain-wall features in Mn3X is, on the other hand, essential for spintronic device engineering. Here, we report an in-depth study on magnetic octupole domain evolution and domain-wall structure with a choice of Mn3Ge single crystal. Our magneto-optical imaging and the anomalous Hall measurements elucidate the nontrivial magnetic octupole domain nucleation, domain-wall propagation, and pinning behaviors. Moreover, combining the micromagnetic simulation, we reveal that Bloch- and Néel-like walls coexist in bulk with comparable sizes and energy densities. Our findings promote understanding the magnetic octupole domain-wall physics and designing domain-wall-based spintronic devices. [ABSTRACT FROM AUTHOR]

Non-collinear antiferromagnet Mn3Sn is a functional material that exhibits the magneto-optical Kerr effect (MOKE) as well as the anomalous Hall effect, arising from the nonvanishing Berry curvature in the broken time-reversal symmetry lattice system likewise the ferromagnets. Mn3Ge, isostructural to Mn3Sn, is also expected to exhibit a similar MOKE but has not been demonstrated yet. In this study, we performed the MOKE measurement in a Mn3Ge single crystal and obtained a large polar MOKE signal (∼8.2 mdeg) and a longitudinal MOKE signal (∼5.6 mdeg). Furthermore, by applying hyperfine polishing and annealing to the surface, we rebuilt a homogenous surface and largely improved the reproducibility of the MOKE signal in Mn3Ge. [ABSTRACT FROM AUTHOR]