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In this article, boundary conditions for Landau–Lifshitz equations at the interface between two ferromagnets with different interfacial Dzyaloshinskii–Moriya interactions (iDMIs) are derived. We calculated and verified the analytical expression for the energy flux density continuity for the spin-wave (SW) propagation through the ferromagnet with stepwise iDMI considering the boundary conditions mentioned. Analytical expressions for reflection, transmission coefficients, and the nonreciprocity factor are calculated in the case of SW propagation through a ferromagnet with the stepwise iDMI. Two different types of nonreciprocity effects for SW propagation through a ferromagnet with the stepwise interface Dzyaloshinskii–Moriya interaction are revealed for opposite orientations of Dzyaloshinskii–Moriya vector. The material parameters of a ferromagnet and the stepwise iDMIs are found for which the extremely high nonreciprocity factor (>10) is expected according to the results of calculations. The results of this article deepen the knowledge about the SW propagation control in magnonic devices. [ABSTRACT FROM AUTHOR]

Unsteady nonlinear magnetization dynamics are studied in an easy-plane ferromagnetic channel subject to spin injection at one edge. The Landau–Lifshitz equation is known to support steady-state solutions, termed dissipative exchange flows (DEFs) or spin superfluids. In this work, by means of numerical simulations and theoretical analysis, we provide a full description of the injection-induced, large-amplitude, nonlinear magnetization dynamics up to the steady state. The dynamics prior to reaching steady state are driven by spin injection, a perpendicular applied magnetic field, the exchange interaction, and local demagnetizing fields. We show that the dynamics result in well-defined profiles in the form of rarefaction waves (RWs), dispersive shock waves (DSWs), and solitons. The realization of these coherent structures depends on the interplay between the spin injection strength and the applied magnetic field. A soliton at the injection boundary, signaling the onset of the magnetic “supersonic” condition, rapidly develops and persists in the steady-state configuration of a contact soliton DEF. We also demonstrate the existence of sustained soliton-train dynamics in long time that can only arise in a nonzero applied magnetic field scenario. The dynamical evolution of spin-injection-induced magnetization dynamics presented here may help guide observations in long-distance spin transport experiments. [ABSTRACT FROM AUTHOR]

DC magnetization, electrical transport, and magnetoresistance (MR) measurements of Fe1–xCoxSi single crystals with $x \approx $ 0.7–0.3 are reported. Fe1–xCoxSi series presents a typical Stoner band excitation characteristic in the field-dependent magnetization profile. Co-doping (x > 0.3) in the Fe1–xCoxSi compound shows a semiconductor–to–metal transition. Enhanced positive MR has been observed when $\sim$ 1/3 of the Fe was substituted with Co, which suggests that the spin density of states in the minor band (semiconductor characteristic) dominates the electronic properties. [ABSTRACT FROM AUTHOR]

We describe the fabrication of a hybrid nanomagneto-electronic device, consisting of a GaAs/AIGaAs quantum wire that is bridged by a ferromagnetic gate, and study the influence of the nanomagnet fringing fields on the quantum-wire magneto-resistance. The nonplanar gate shows clear single-domain structure in magnetic-force microscopy, and a simple magnetization behavior in an external magnetic field. This behavior is reflected as a hysteretic variation of the quantum-wire magneto-resistance, whose magnitude is found to be consistent with theoretical predictions for ballistic electron transport through a spatially varying magnetic field. [ABSTRACT FROM AUTHOR]

Measurements of magnetic relaxation isotherms were performed as a function of magnetic field and temperature on an exchange- bond-disordered ferromagnetic perovskite Ca0.2Sr0.8RuO3, over an observation time window 10 s ≤ t ≤ 104 s, and over a wide range of temperatures which spanned the entire irreversible phase. A plot of Tln(tr/τ/τ0) as a function of holding field -Ha was constructed from the times tr at which the measured relaxation isotherms reversed sign. The plot was interpreted with the aid of numerical simulations based on a model collection of two-level subsystems, which showed that the temperature dependence of the magnetic response of this perovskite was shaped by the coexistence of thermal fluctuations and the explicit evolution of the free energy landscape with temperature, and which yielded estimates for the thermal fluctuation field and for the mean intrinsic dissipation barrier as functions of temperature. [ABSTRACT FROM AUTHOR]