The requirements for imaging magnetic vortices properly by magnetic force microscopy are discussed. Special attention is devoted to the influence of the tip on the sample magnetic configuration. It is shown that one can obtain a quantitative understanding of the experiments using micromagnetic simulations within a general framework for reversible tip-induced perturbations. Finally, preliminary results obtained with specially prepared 'nanowire tips' are presented.

Magnetic nanopatterning of perpendicular hard disc media with perpendicular anisotropy, but preserving disc surface planarity, is presented here. Reactive ion implantation is used to locally modify the chemical composition (hence the magnetization and magnetic anisotropy) of the Co/Pd multilayer in irradiated areas. The 1 Corresponding author 2 procedure involves low energy, chemically reactive ion irradiation through a resist mask. Among N, P and As ions, P are shown to be most adequate to obtain optimum bit density and topography flatness for industrial Co/Pd multilayer media. The effect of this ion contributes to isolate perpendicular bits by destroying both anisotropy and magnetic exchange in the irradiated areas. Low ion fluences are effective due to the stabilization of atomic displacements levels by the chemical effect of covalent impurities.Key words: hard drive, perpendicular magnetic recording, CoPd multilayers, multilayer media, nanoimprint lithography. I.-IntroductionData storage is dominated by disc based magnetic recording technology that combines high capacity, reasonable read/write speeds and cost-effectiveness. The storage density has increased spectacularly through the last years as the ability to reduce magnetic bit volumes has improved. However, as the volume is reduced the magnetic anisotropy energy becomes compatible with the thermal energy k B T (superparamagnetic limit) and the magnetic information of the bits gets lost. New technologies and strategies are needed to postpone or circumvent this limit, , high anisotropy chemically synthesized nanoparticles media 7,8 ,to name a few. A review on fabrication challenges for patterned recording media has been published recently. 9Patterned perpendicular magnetic media is a combination of methods being investigated to further extend areal bit densities. 4,10,11 In this approach, the data are recorded and stored in an array of single-domain magnetic bits ("nanomagnets") that The use of ion irradiation through a mask to modify the magnetic properties of films is also of current interest. In particular, this last case has been studied in detail by Chappert et al. 25; Ferre et al. . These ions were selected since they could be divided into two types: chemically inert with Co or Pd (N) and chemically active like (P, As), since they can form a covalent bond with cobalt from the alloy.The ion stopping masks were defined by e-beam lithography by use of a Leica EBPG 5000+ working at 100 keV. For this purpose, a negative resist (MAN 2403) was spun onto the samples, with an optimum thickness sufficient to stop each type of ion, so the underlying magnetic layer is protected during the irradiation process except in those areas where the resist was removed. Prior to this step some gold marks were deposited on the sample to define arrays in order to locate the nanostructured areas for measurements purposes. After implantation, the resist mask was removed by oxygen plasma cleaner.Structural modifications were studied by X-ray diffraction (XRD) using a P...

The magnetic properties of tilted easy axis L1 0 CoPt(1 1 1)/Pt(1 1 1)/MgO(1 0 0) film, deposited by pulsed laser deposition, were investigated by magnetization angular dependence measurements and magnetic force microscopy (MFM). The room temperature anisotropy constant, evaluated measuring the in-plane variation of transverse magnetization under a rotating magnetic field, is K 1 = 5 × 10 6 erg cm −3. The domain structure, observed by MFM, consists of decoupled single domain grains, unlike the maze-like structure usually observed for similar systems. This was confirmed by the analysis of dc demagnetization and isothermal remanence magnetization curves, which provided evidence of predominant magnetostatic interactions.