Fundamentals for magnetic patterning by ion bombardment of exchange bias layer systems

Abstract

In the present paper we investigate whether the ion bombardment induced magnetic modifications in exchange biased bilayers are stable in time, whether the direction of the exchange bias can be set to any arbitrary (in-plane) direction by the ion bombardment and whether the exchange bias field can be changed in successive bombardment steps. These three fundamental characteristics are prerequisites for ion bombardment used for an efficient, practical, and stable magnetic patterning of exchange biased layer systems.

Tailoring coercivity of unbiased exchange-coupled ferromagnet/antiferromagnet bilayers

“…Since the electronic stopping power predominates for 40 keV He þ irradiation, its main effect is local hyperthermal heating trigged by electronic excitations. 32 This is confirmed by Fig. 5 where the estimated via SRIM simulations depth profiles of the damages caused by 40 keV He þ , Ar þ , or Ge þ irradiations into Si/NiCr/IrMn/NiCu/Cr films are shown.…”

Stray fields above artificial magnetic in-plane domains

“…After development of the resist in a 0.9% KOH solution a parallel-stripe structure results, consisting of 5 mm wide resistcovered and 5 mm wide resist-free stripes both having their long axes perpendicular to the initial EB field direction. The thickness of the resist was chosen to prevent 10 keV He þ ions to reach the sample surface in the subsequent bombardment step [14,15,[22][23][24]. The ion bombardment was performed through the resist mask using a home-built plasma source [25].…”

Magnetic patterning by means of ion irradiation and implantation

“…In many cases noble gas ion irradiation was performed in an applied magnetic field in order to alter the direction and amplitude of unidirectional anisotropy [26][27][28][29]31,32,35,40,[43][44][45][46]. In other experiments the exchange bias was only reduced or diminished locally by ion irradiation [24,33,41], thus resulting in regions of different exchange bias strength, but not, for instance oppositely aligned exchange bias.…”