Influence of ion irradiation on switching field and switching field distribution in arrays of Co/Pd-based bit pattern media

Thomas Hauet (1, 2) , O Hellwig (2) , S.-H Park (3) , C Beigné (4) , E Dobisz (2) , B.D. Terris (2) , D Ravelosona (3)

1 IJL - Institut Jean Lamour
2 HGST San Jose Research Center
3 IEF - Institut d'électronique fondamentale
4 CEA - Commissariat à l'énergie atomique et aux énergies alternatives

We have used ion irradiation to tune switching field and switching field distribution ͑SFD͒ in polycrystalline Co/Pd multilayer-based bit pattern media. Light He + ion irradiation strongly decreases perpendicular magnetic anisotropy amplitude due to Co/Pd interface intermixing, while the granular structure, i.e., the crystalline anisotropy, remains unchanged. In dot arrays, the anisotropy reduction leads to a decrease in coercivity ͑H C ͒ but also to a strong broadening of the normalized SFD/ H C ͑in percentage͒, since the relative impact of misaligned grains is enhanced. Our experiment thus confirms the major role of misorientated grains in SFD of nanodevice arrays. Today a major research effort in magnetism is targeted toward achieving ultrahigh density data storage with nano-scale magnets. Spin-transfer magnetic random access memory ͑spin-RAM͒ and bit patterned media ͑BPM͒ technologies are currently part of the most promising media. The implementation of both of these technologies relies on achieving in-detail physical understanding and control of the magnetization reversal mechanism in each nanoscopic individual bit to ensure reproducibility of the bit properties in order to avoid write errors. Perpendicular magnetic anisotropy ͑PMA͒ materials, such as polycrystalline Co/Pd, Co/Pt, and Co/Ni multilayers, are believed to be promising materials for both spin-RAM and BPM applications. 1–4 Indeed, they have a well defined high amplitude uniaxial anisotropy that provides good thermal stability while offering low critical current in spin-transfer devices 2 and tunable switching fields in BPM. 4

Mots clés: magnetic thin film; switching field distribution; bit pattern media; magnetic recording; ion irradiation

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Thomas Hauet, O Hellwig, S.-H Park, C Beigné, E Dobisz, et al.. Influence of ion irradiation on switching field and switching field distribution in arrays of Co/Pd-based bit pattern media. Applied Physics Letters, 2011, ⟨10.1063/1.3581896⟩. ⟨hal-01345352⟩