Dresden 2009 – scientific programme
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MA: Fachverband Magnetismus
MA 40: Poster II: Bio- and Molecular Magnetism (1-9); Magnetic Coupling Phenomena/Exchange Bias (10-15); Magnetic Particlicles and Clusters (16-29); Micro and Nanostructured Magnetic Materials (30-51); Multiferroics (52-64); Spin Injection in Heterostructures (65-67); Spin-Dyn./Spin-Torque (68-93); Spindependent Transport (94-108)
MA 40.80: Poster
Friday, March 27, 2009, 11:00–14:00, P1A
Laser-Induced Generation and Quenching of Magnetization on FeRh Investigated with Time-Resolved X-ray Magnetic Circular Dichroism — •Ilie Radu1,2, Christian Stamm2, Niko Pontius2, Torsten Kachel2, Paul Ramm1, Jan-Ulrich Thiele3, Hermann Dürr2, and Christian Back1 — 1Regensburg University, Regensburg, Germany — 2BESSY GmbH, Berlin, Germany — 3Hitachi Global Storage, San Jose, CA, USA
Upon heating, the equiatomic FeRh alloy exhibits a first-order magnetic phase transition from the antiferromagnetic (AFM) to the ferromagnetic (FM) state around room temperature. Here, we study the fs laser-induced AFM-FM phase transition as well as the transition from FM towards the paramagnetic state by employing the time-resolved X-ray magnetic circular dichroism. Both Fe and Rh elements show a gradual growth of the magnetic moment within 200 ps after laser excitation. Temperature-dependent data, measured at intermediate temperatures between AFM and FM state, provide evidence for the rapid nucleation and subsequent slow expansion of the FM regions within an AFM matrix, supporting the magnetization growth model proposed in [1]. Once in the FM state, FeRh can be optically demagnetized on a few ps time scale (limited by the X-ray probing pulse). Further time-resolved magneto-optics measurements done in the visible spectral range reveal a demagnetization time constant of ~200 fs. For the photo-induced demagnetization process we consider a mechanism that follows the transient electronic structure of the system.
[1] B. Bergmann et al., PRB 73, 060407(R) (2006)