Optically induced magnetization dynamics and variation of damping parameter in epitaxialCo2MnSiHeusler alloy films

Abstract

All-optical pump-probe measurements of magnetization dynamics have been performed upon epitaxial Co 2 MnSi͑001͒ Heusler alloy thin films annealed at temperatures of 300, 400, and 450°C. An ultrafast laserinduced modification of the magnetocrystalline anisotropy triggers precession which is detected by timeresolved magneto-optical Kerr effect measurements. From the damped oscillatory Kerr rotation, the frequency and relaxation rate of the precession is determined. Using a macrospin solution of the Landau-Lifshitz-Gilbert equation the effective fields acting upon the sample magnetization are deduced. This reveals that the magnetization is virtually independent of the annealing temperature while the fourfold magnetocrystalline anisotropy decreases dramatically with increasing annealing temperature as the film structure changes between the B2 and L2 1 phases. From the measured relaxation rates, the value of the apparent Gilbert damping parameter is found to depend strongly upon the static field strength and in-plane static field orientation. The variation of the apparent damping parameter is generally well reproduced by an inhomogeneous broadening model in which the presence of B2 and L2 1 phases leads to a large dispersion of the magnetocrystalline anisotropy. However, for the sample annealed at a temperature of 300°C, the lack of a detailed fit to the data suggests that the apparent anisotropy of the apparent damping parameter might alternatively arise due to a network of dislocations with fourfold symmetry.

The essential role of carefully optimized synthesis for elucidating intrinsic material properties of (Ga,Mn)As

“…1 is 500 nm thick. Its magnetization and transport Curie point singularities are largely smeared out, the damping factor is strongly frequency dependent 13 , and alternating number of SWRs is observed with increasing applied field whose spacings are inconsistent with Kittel modes. Clearly, the material is non-uniform, the magnetization and transport data indicate strong moment and charge compensation by extrinsic impurities, and for this material it is impossible to reliably extract any of the intrinsic micromagnetic parameters of (Ga,Mn)As.…”

Static and dynamic magnetic properties of densely packed magnetic nanowire arrays

“…TRMOKE measurements were made to investigate the optically induced magnetization dynamics and transient reflectivity of the samples. In this particular pump-probe measurement technique, 53 a Ti:sapphire regenerative amplifier laser system was used to generate pulses of 800 nm wavelength, at 100 kHz repetition rate, with an intensity autocorrelation of 82 fs that corresponds to a hyperbolic secant pulse shape of 53 fs width. Each pulse was split into a pump and probe part.…”

Structural and magnetic properties of Co2MnSi thin films

“…Due to the attractive potential of CMS for spintronics applications, particularly in order to produce magnetic random access memories (MRAMs), its dynamic behavior within the 1-10 GHz frequency range, which, in this technology, is a key in view of increasing data rates in magnetic storage devices, is actively studied [14][15][16][17]. However these studies are mainly focused on CMS thin films grown on MgO or GaAs substrates which provide a less complicated crystal texture than the Al 2 O 3 substrates.…”