Regensburg 2010 – scientific programme
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MA: Fachverband Magnetismus
MA 14: Spin Dynamics / Spin Torque I
MA 14.12: Talk
Wednesday, March 24, 2010, 12:30–12:45, H10
Probing half-metalicity of Co2FexMn1−xSi Heusler films in all-optical pump-probe experiments — •Jakob Walowski1,2, Andreas Mann1, Markus Münzenberg1, Shigemi Mizukami3, Takahide Kubota2, Mikihiko Oogane2, Hiroshi Naganuma2, Yasuo Ando2, and Terunobu Miyazaki3 — 1I. Physikalisches Institut, Universität Göttingen, Germany — 2Department of Applied Physics, Graduate School of Engineering, Tohoku University, Sendai, Japan — 3WPI-AIMR, Tohoku University, Sendai, Japan
Half metals are a promising candidate as spin injectors for spintronic devices, because of a high spin polarization at Fermi level and low Gilbert damping α. All-optical TRMOKE enables us to determine the degree of spin polarization by exciting the electrons above the Fermi level and probing the demagnetization time τm. Because of a band gap for minority electrons at Fermi level, Elliott-Yafet scattering processes are blocked, τm increases to the ps regime. From the increased τm the degree of spin polarization and thus a half-metallic behavior can be concluded. A second time scale τα , which describes the decline of magnetization precession (∼1 ns) started by an anisotropy change during the excitation allows the determination of α. We studied magnetization dynamics on both timescales in epitaxial Co2FexMn1−xSi samples by systematically increasing the Fe content in steps of 0.2. The samples reveal a spin polarization around 80% and α<0.01. Both parameters are sensitive to the quality of the sample structure.
Financial support from MEXT and NEDO Spintronics Nonvolatile Devices Project and a DAAD scholarship and is greatly acknowledged.