| AVS 62nd International Symposium & Exhibition | |
| Thin Film | Friday Sessions |
| Session TF+MI-FrM |
| Session: | Thin Films for Light Trapping, Plasmonic, and Magnetic Applications |
| Presenter: | Dieter Weller, HGST a Western Digital company |
| Authors: | J-Y. Bigot, Institut de Physique et Chimie des Matériaux de Strasbourg: Université de Strasbourg and CNRS, France J. Kim, Institut de Physique et Chimie des Matériaux de Strasbourg: Université de Strasbourg and CNRS, France M. Vomir, Institut de Physique et Chimie des Matériaux de Strasbourg: Université de Strasbourg and CNRS, France O. Mosendz, HGST a Western Digital company S. Jain, HGST a Western Digital company D. Weller, HGST a Western Digital company |
| Correspondent: | Click to Email |
Implementing larger and faster recording capacities, like in Heat Assisted Magnetic Recording (HAMR) devices, requires investigating the magnetization dynamics of nanostructures at the sub-picosecond time scale. The case of L10 FePt “nanocrystals” is of particular interest as HAMR media can be designed with grain diameter below today’s D ~ 8 nm. The magnetic anisotropy is sufficiently high and results in coercive fields larger than 5 Tesla at room temperature [1, 2].
Femtosecond magneto-optics allows investigating the dynamical properties of such films [3] and nanoparticles [4] with a temporal resolution well adapted to the actual needs of performant materials that can be addressed in the time scale of a few picoseconds or faster. In the case of materials for HAMR, the pre-heating with femtosecond laser pulses allows reaching very high electron temperatures beyond the Curie point without over heating the lattice. It is therefore a relevant approach to use femtosecond pulses as it allows improving the conditions for obtaining an efficient switching due to the laser pre-heating. In that context, the variation of the coercive field Hc and magnetization at saturation MS are important quantities to be characterized. We have investigated such dynamics in L10 FePt nanoparticles and accurately characterized the nonlinear variation of MS and Hc upon varying the laser density of energy. We demonstrate that the Curie temperature can be reached during a few hundreds of femtoseconds, showing that the speed for addressing bits of information can be further improved in ultrafast HAMR applications.
[1] O. Mosendz, et al., J. Appl. Phys. 111, 07B729 (2012)
[2] D. Weller et al., Phys. Stat. Solidi A 210, 1245 (2013)
[3] S. Wicht et al., J. Appl. Phys. 114, 063906 (2013) & J. Appl. Phys. 117, 013907 (2015)
[4] E. Beaurepaire, J.-C. Merle, A. Daunois, J.-Y. Bigot, Phys. Rev. Lett. 76, 4250 (1996)
[5] J.-Y. Bigot, M. Vomir, Annalen der Physik 525, 2–30 (2013)