Strain and Thermally Induced Magnetic Dynamics and Spin Current in Magnetic Insulators Subject to Transient Optical Grating

Abstract

We analyze the magnetic dynamics and particularly the spin current in an opencircuit ferromagnetic insulator irradiated by two intense, phase-locked laser pulses. The interference of the laser beams generates a transient optical grating and a transient spatiotemporal temperature distribution. Both effects lead to elastic and heat waves at the surface and into the bulk of the sample. The strain induced spin current as well as the thermally induced magnonic spin current are evaluated numerically on the basis of micromagnetic simulations using solutions of the heat equation. We observe that the thermo-elastically induced magnonic spin current propagates on a distance larger than the characteristic size of thermal profile, an effect useful for applications in remote detection of spin caloritronics phenomena. Our findings point out that exploiting strain adds a new twist to heat-assisted magnetic switching and spin-current generation for spintronic applications.

Stratonovich-Ito integration scheme in ultrafast spin caloritronics

“…The relation of the pulse parameters and the value of the temperature has been discussed in details in Ref. [6]. The thermal bias through the mismatch between magnon temperature T m F and the sample temperatures T F drives the magnonic spin current of interest here.…”

“…These observations are related to ultrafast spin dynamics [4,5] and depend on the parameters of the driving fields such as their intensity, duration, and frequencies, we well as on the inherent properties of the magnetic sample. Our interest here is devoted to a particular aspect namely to the non-equilibrium magnonic current generated by a temperature gradient due to local heating of the sample by a laser pulse [6]. This means that we concentrate on the regime where the phonon temperature profile has already been established and consider the nonequilibrium dynamics of magnons.…”

Femtosecond laser driven precessing magnetic gratings

“…15 Considering the fact that spin dynamics are sensitive to inhomogeneous spatiotemporal temperature distributions, 16 TGS can be predicted to form a sensitive probe of ultrafast magnetization dynamics. A few pioneering works have studied TG-induced magnetic excitation of surface magnetoelastic waves, 16 spin currents 17 and writing of strip domains. 18 However, TG-induced ultrafast dynamics of magnetic systems have been sparsely investigated at large, although it may be expected to provide rich physics and hold potential applications within e.g.…”

Thermoelastic enhancement of the magnonic spin Seebeck effect in thin films and bulk samples

“…Thus, the magnetoelastic gap is usually quite small compared to the gap in the magnonic spectrum which is induced for instance by a magnetocrystalline anisotropy or by external field terms. A thermal heating leading to a steady state elastic deformation may serve as an alternative for activating (magneto) elastic modes that occur in ferromagnetic films and heterstructures [7][8][9][10][11][12][13][14][15][16][17]. Elasticity involving nonisothermal deformations is part of the well-established field of thermoelasticity [18,19].…”