Broad-Band FMR Linewidth of Co ₂ MnSi Thin Films with Low Damping Factor: The Role of Two-Magnon Scattering

Abstract

The low Gilbert damping factor, which is usually measured by ferromagnetic resonance, is crucial in spintronic applications. Two-magnon scattering occurs when the orthogonality of the ferromagnetic resonance mode and other degenerate spin wave modes was broken by magnetic anisotropy, voids, second phase, surface defects, etc., which is important in analysis of ferromagnetic resonance linewidth. Direct fitting to linewidth with Gilbert damping is advisable only when the measured linewidth is a linear function of measuring frequency in a broad band measurement. We observe the nonlinear ferromagnetic resonance linewidth of Co2MnSi thin films with respect to measuring frequency in broad band measurement. Experimental data could be well fitted with the model including two-magnon scattering with no fixed parameters. The fitting results show that two-magnon scattering results in the nonlinear linewidth behavior, and the Gilbert damping factor is much smaller than reported ones, indicating that our Co2MnSi films are more suitable for the applications of spin transfer torque.

Interplay of large two-magnon ferromagnetic resonance linewidths and low Gilbert damping in Heusler thin films

“…In recent years it has been realized that TMS linewidths are pervasive for the conventional in-plane geometry of thin film FMR measurements, requiring either the perpendicularto-plane FMR geometry [13] (for which TMS processes are suppressed) or sufficiently broadband measurements [14] to extract the bare Gilbert α. For instance, recent FMR linewidth studies on Heusler compounds have reported distinct TMS linewidths [15,16], which challenged simple inference of the Gilbert α.…”

Voltage control of ferromagnetic resonance and spin waves

“…The TMS effect is usually manifested as FMR fields changing or linewidth broadening [84,86] and widely exists in various ferromagnets. [85][86][87]90] Xue et al confirmed the voltage tuning of TMS in Ni 0.5 Zn 0.5 Fe 2 O 4 (NZFO)/ PMN-PT(011) multiferroic heterostructures fabricated by PLD. [91] Owing to the in-plane anisotropy of the PMN-PT(011) slabs, the voltage modification of the TMS was divided into two modes as the magnetic field was parallel to the (100) or (0 11) plane of the PMN-PT substrates, respectively.…”

Ferromagnetic resonance of facing-target sputtered epitaxial γ′-Fe4N films: the influence of thickness and substrates

“…where α int is the Gilbert damping constant, γ is the gyromagnetic ratio, f is the microwave frequency, and ΔH 0 is the inhomogeneous linewidth. One can see from equation ( 4) that ΔH int is linear to f. However, ΔH TMS is not linear to f [20][21][22][23][24][25].…”

“…TMS linewidth is induced by the defects and impurities on the surface and interface of ferromagnets. The TMS process plays a very important role in ferromagnetic relaxation, which sometimes can even be dominant [20][21][22][23][24][25]. In this work, epitaxial γ′-Fe 4 N films with a film thickness ranging from 8.5-170.0 nm were deposited on MgO, SrTiO 3 , and LaAlO 3 substrates.…”