Nano-patterning of perpendicular magnetic recording media by low-energy implantation of chemically reactive ions

Abstract

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...

Ion beam induced surface and interface engineering

“…1.16 [69]. They have been used reactive ion implantation to locally modify the chemical composition (hence the magnetization and magnetic anisotropy) of the Co/Pd multilayer in irradiated areas.…”

Understanding the Magnetic Microstructure through Experiments and Machine Learning Algorithms

“…The ions lose energy during their passage through the material, which is either spent in displacing the target atoms by elastic collision (nuclear stopping) or exciting the atoms by inelastic collisions (electronic stopping) . A large variety of studies exists on ion-beam induced modifications in magnetic ML, either in the context of patterning or depth-resolved structural modifications. , The creation of graded anisotropy media by domain wall positioning has also been reported using ion irradiation . Ion-induced modification of magnetic properties with depth-resolved structural studies in Co/Pt ML has been reported. , An interesting study on the investigation of magnetic domains after ion beam irradiation was performed by Trassinelli et al, where local microscopic features of domains were highlighted in the vicinity of the ferromagnetic to paramagnetic phase transition temperature for Mn–As thin films .…”

“…The ions lose energy during their passage through the material, which is either spent in displacing the target atoms by elastic collision (nuclear stopping) or exciting the atoms by inelastic collisions (electronic stopping). 28 A large variety of studies exists on ion-beam induced modifications in magnetic ML, either in the context of patterning 29 or depth-resolved structural modifications. 30 , 31 The creation of graded anisotropy media by domain wall positioning has also been reported using ion irradiation.…”

Влияние морфологии на механизмы перемагничивания многослойных тонких пленок Co/Pd

“…Неоднократно показано, что увеличение значений H a и H C , характеризующих свойство ПМА многослойных структур Co/Pt и Co/Pd, может быть достигнуто подбором оптимальных толщин слоев, а также их количества [7,8]. Соблюдение периодичности слоев Со и Pd (Pt) с заданной толщиной, которая, как правило, не превышает 2−5 ¦ , т. е. один или несколько монослоев, позволяет формировать на их основе сверхрешетки [9], квазисплавы из перемешанных компонентов Со и Pd (Pt) [5], которые упорядочиваются в магнитные структуры с ПМА самостоятельно либо под воздействием последующей обработки (отжиг, обучение ионами) [1,10,11]. Формирование в таких системах развитых интерфейсов Co/Pt и Co/Pd помимо усиления ПМА может приводить также к увеличению их намагниченности вследствие спиновой поляризации атомов Pt и Pd [12,13].…”