Planar patterned magnetic media obtained by ion irradiation

Science

Volumn 280, Issue 5371, 1998, Pages 1919-1922

  Chappert, C ^a   Bernas, H ^a   Ferre J ^b   Kottler, V ^a,c   Jamet, J P ^b   Chen, Y ^c   Cambril, E ^c   Devolder, T ^a   Rousseaux, F ^c   Mathet, V ^a   Launois, H ^c  

^a UNIVERSITÉ PARIS SACLAY   (France)

^b UNIVERSITÉ PARIS SUD   (France)

^c Lab Microstructures Microlectron   (France)

Author keywords

[No Author keywords available]

Indexed keywords

COBALT; PLATINUM;

ARTICLE; INFORMATION PROCESSING; ION TRANSPORT; IRRADIATION; MAGNETIC FIELD; PRIORITY JOURNAL; RECORDING; STORAGE;

EID: 0032547079     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.280.5371.1919     Document Type: Article

References (31)

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19. -3 mbar), which gives a flat continuous polycrystalline film with nearly perfect (111) texture and small (∼7 nm) gram size. Then rf diode and rf magnetron, respectively, are used for deposition of the Co and Pt layers at around 0.02 nm/s, terminating all samples with a 3.4-nm R coverage layer. AFM measurements show a root mean square roughness of the Pt buffer layer around 0.2 nm, which is preserved on the topmost surface (Pt coverage layer) for all samples.
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26. We have not yet studied these limits experimentally but have performed simulations (T. Devolder et al., unpublished data) to determine the length (hereafter called "transition length") over which ion-induced structural changes occur at a mask edge. The limiting factor of the transition length is not the ion beam angular spread but the ion beam lateral straggling values at the Pt-Co layer depth, which in turn depend on the mask thickness seen by the ion beam in case of incomplete stopping. To determine the effect of a lithographically made irradiation mask on the transition length, we performed calculations for a PMMA stripe (200 nm wide, 600 nm high, with both a vertical-and a pyramid-based edge profile deduced from scanning electron micrographs of real masks). Transition length estimates were obtained by convoluting mask shapes corresponding to our experimental conditions with lateral straggling values deduced from TRIM simulations (79). Depending on the exact shapes assumed for the former, the obtainable lateral resolution for PMMA masks varied from 100 nm (worst case) to 20 nm (best case). We anticipate that even lower values (down to about 5 nm or less) might be obtained by using more appropriate masks and patterning techniques; see, for example, [R. M. H. New, R. F. W. Pease, R. L. White, J. Vac. Sci. Technol. B 12, 3196 (1994)]. The fact that the magnetic property changes are not related in a simple way to the ion-induced structural changes must be considered. In separate studies (unpublished data) of unmasked Co-Pt structures, we determined the ion fluence dependence of the Kerr rotation and the anisotropy, from which we can estimate the transition length for magnetic property changes. We find that in most cases the magnetic transition will be sharper than the structural one.
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31. We thank O. Kaitasov and S. Gautrot for technical assistance. This work was performed within the framework of the ISARD collaboration (Université Paris-Sud). V. K. is funded by a Marie-Curie grant from the European Union.