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Magnetization orientation in Ga+-irradiated Pt/Co(dCo)/Pt ultrathin films can be changed in a controlled way by adjusting the ion fluence, F. Two-dimensional (dCo, F) diagrams of magnetic and magneto-optical properties have been derived. Distinct out-of-plane magnetic anisotropy states with enhanced magneto-optical effects were evidenced for specific (dCo, F) values. This rich behavior originates from two competing mechanisms: intermixing of Co and Pt atoms at the interfaces and the formation of ordered CoPt alloy phases with high magnetic anisotropy. The irradiation-induced effects open novel routes for both tailoring thin-film magnetic and magneto-optical properties and patterning of magnetic nanostructures [ABSTRACT FROM AUTHOR]

A patterned buffer fabricated as Au islands self-assembled on an Mo layer surface locally affects magnetic properties (magnetic anisotropy, coercivity) of a deposited Co ultrathin layer. As a consequence, a system of elevated magnetic dots of a hundred nanometers in lateral size embedded in a magnetic matrix is obtained. Magnetization reversal of the patterned structure and magnetic states of individual dots are investigated by means of polar magnetooptical Kerr magnetometry and magnetic force microscopy, respectively. Despite a size distribution and the various shapes the perpendicularly magnetized dots adopt a monodomain state. [ABSTRACT FROM AUTHOR]

The origin of magnetic phase transition from in-plane to perpendicular magnetic anisotropy (PMA) of Pt/Co/Pt thin film by Ga+ ion irradiation at fluences of 1-5×1015ions/cm² is investigated by means of x-ray magnetic circular dichroism (XMCD) and extended x-ray absorption fine structure (EXAFS) analyses. We find that Pt and Co atoms are mixed with each other and that Co is oxidized near the surface due to removal of the Pt overlayer. Furthermore, polarization-dependent EXAFS analysis shows that Co is firstly dispersed as separated single-atom-thick sheets in a Pt matrix at 1×1015 ions/cm², then the Co sheets are divided into a few Å clusters at 5×1015 ions/cm², which are regarded as nanodiscs parallel to the film plane. This process is accompanied by the appearance of an out-of-plane magnetization component and a remanence peak is observed. Because we do not observe an enhancement in anisotropy of Co orbital moment which leads to change in magnetic anisotropy through the transition at about 5×1015 ions/cm², it might be possible that such nanodisc formation induces increase of magnetic anisotropy via a shape effect. By comparing with the phase transition observed at lower fluence [Phys. Rev. B 86, 024418 (2012)], we find that the mechanism of two transitions is different, i.e., the transition at lower fluence is caused by anisotropy of orbital moment due to structural strain, while the present transition is possibly by shape effect due to nanodisc formation. [ABSTRACT FROM AUTHOR]

Defined perpendicular anisotropy gradients in the Co sublayers of a [Co(0.6  nm)/Au(2  nm)](3) sputter-deposited multilayer have been introduced by light ion bombardment through a wedged Au stopper layer. Within such a layer system, domain walls between up- and down-magnetized areas are controllably movable by an external perpendicular homogeneous magnetic field. This method and layer system is very promising for a controlled magnetic particle transport within the stray fields of the moving domain walls.