Strain‐Controlled Spin Wave Excitation and Gilbert Damping in Flexible Co₂FeSi Films Activated by Femtosecond Laser Pulse

Abstract

The dynamic response of magnetic order to optical excitation at sub‐picosecond scale has offered an intriguing alternative for magnetism manipulation. Such ultrafast optical manipulation of magnetism has become a fundamental challenging topic with high implications for future spintronics. Here, this study demonstrates such manipulation in Co2FeSi films grown on flexible polyimide substrate, and demonstrates how the magneto‐optical interaction can be modified by using strain engineering which in turn triggers the excitation of both dipolar and exchange spin waves modes. Furthermore, Gilbert damping and spin‐orbit coupling in Co2FeSi can both be tuned significantly by altering the magnitude and type of applied strain, suggesting an appealing way to manipulate spin wave propagation. These results develop the optical manipulation magnetism into the field of spin wave dynamics, and open a new direction in the application of spin orbitronics and magnonics devices using strain engineering.

Colossal Gilbert Damping Anisotropy in Heusler‐Alloy Thin Films

“…Furthermore, to gain insights into the origin of such colossal Gilbert damping anisotropy, a practical criterion of intrinsic damping is described by Kambersky's torque‐correlation model [ 43 ] for transition metal ferromagnetic material, i.e., $$\alpha \; \sim \;N({E_{\rm{F}}}){\xi ^2}$$, where N ( E F ) is the density of state (DOS) at Fermi level and ξ is the SOC parameter. In order to check the role of N ( E F ), first‐principles calculations were done for the ordered B2 phase supercell, as shown in Figure S6 (Supporting Information).…”

“…Both resonance fields H r and linewidths ΔH increase markedly from the easy axis to the hard axis. In addition, for easy axis [110] direction, it is notable that an additional resonance mode, i.e., perpendicular standing spin wave (PSSW) mode, [42][43][44] was excited at a lower resonance field, [42,45] which may be attributed to the surface partial spin pinning affected by anisotropy field. [45][46][47] Figure 3c,d shows the frequency and angular dependence of the resonance field H r .…”

“…[56] Such ultralow damping may be determined by the half-metallicity of Co 1.4 Fe 1.6 Al film discussed later, for which the spin-minority channel has no contribution to the damping. [5] Furthermore, to gain insights into the origin of such colossal Gilbert damping anisotropy, a practical criterion of intrinsic damping is described by Kambersky's torque-correlation model [43] for transition metal ferromagnetic material, i.e., N E ( )…”

Highly efficient heat-dissipation power driven by ferromagnetic resonance in MFe2O4 (M = Fe, Mn, Ni) ferrite nanoparticles

“…In order to further maximize the power loss, such critical magnetic parameters can be tailored optimally through the existing novel engineering techniques: saturation magnetization can be increased by substitution of transition metal ions in iron-oxides 34 , synthesis of bimagnetic core–shell materials 35 , or the thermolysis process 36 . Also, Gilbert damping constants can be reduced by the annealing process 37 , the optimal stoichiometric composition 38 , 39 , the strain-engineered process 40 , or other means. The measured temperature increments were also well controllable with low-magnetic-field-strength parameters.…”

Low Threshold and Robust Ultrafast Pulses from Freestanding‐Growth 2D Quaternary BiCuSeO

“…Ultrafast fiber lasers, as solid‐state bulk lasers alternatives, have found wide applications in micromachining, biomedicine, ultrafast physics, multiphoton microscopy, and spectroscopy. [ 1–11 ] Saturable absorber is a crucial component to achieve robust mode‐locked operation in ultrafast pulsed laser. Semiconductor saturable absorber mirrors (SESAMs) are efficient and commonly used saturable absorbers in various laser systems, initially introduced by Keller in 1991.…”