Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Ion beam irradiation enables to modify magnetic properties of magnetic ultrathin films and multilayers [1, 2]. Such a method is a very promising technique for magnetic patterning [3]. In films with initial perpendicular magnetization the decrease of perpendicular magnetic anisotropy, followed by the magnetization rotation to the in-plane orientation and finally a transition to superparamagnetic state has been observed with increasing irradiation dose D [1-3]. Recently a double magnetisation reorientation from in-plane to out-of-plane direction and back to in-plane alignment, driven by Ga+ ion 30 keV irradiation, has been observed in sputtered Pt/(Co 2.6 nm)/Pt films [4].
In this work we report the influence of focused ion beam (FIB) irradiation on magnetic properties of MBE grown Mo/Pt/(Co 3.3nm)/Pt sandwiches. In the as deposited sample magnetization was aligned in the film plane. The numerous areas of the sample (squares 100x100μm² or 50x50μm²) have been irradiated by Ga+ ions with doses D ranging between 2x10¹² and 1x10¹⁶ ions/cm². A development of perpendicular magnetic anisotropy in irradiated regions has been correlated with modifications of a surface morphology using polar Kerr effect magnetometry (sensitive to perpendicular magnetization component), as well as atomic/magnetic force microscopy techniques.

[1] C. Chappert, H. Bernas, et al., Science 280, 1919 (1998).
[2] J. Fassbender, J. McCord, J. Magn. Magn. Mat. 320, 579 (2008).
[3] J. Ferré, J.-P. Jamet, in Handbook of Magnetism and Advanced Magnetic Materials, Vol. 3, p.1710 H. Kronmüller, S. Parkin Ed. (John Wiley & Sons, Ltd, 2007).
[4] J.Jaworowicz et al., APL 95, 022502 (2009).