Magnetic stripes and holes: Complex domain patterns in perforated films with weak perpendicular anisotropy

F Valdés-Bango,L M Alvarez-Prado,M Vélez,J M Alameda,J I Martín

doi:10.1063/1.4973284

F Valdés-Bango, L M Alvarez-Prado + Show 3 more

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https://doi.org/10.1063/1.4973284

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Abstract

Hexagonal antidot arrays have been patterned on weak perpendicular magnetic anisotropy NdCo films by e-beam lithography and lift off. Domain structure has been characterized by Magnetic Force Microscopy at remanence. On a local length scale, of the order of stripe pattern period, domain configuration is controlled by edge effects within the stripe pattern: stripe domains meet the hole boundary at either perpendicular or parallel orientation. On a longer length scale, in-plane magnetostatic effects dominate the system: clear superdomains are observed in the patterned film with average in-plane magnetization along the easy directions of the antidot array, correlated over several antidot array cells.

Highlights

Magnetic antidots have often been used to tailor the magnetic properties of extended films:[1,2,3,4,5,6,7,8,9,10,11,12] Depending on hole size and array geometry, they can enhance DW pinning,[2] modify magnetic anisotropy and easy axis direction[3] or, even, create ratchet effects on DW propagation.[4]
We have studied the effects of the magnetostatic shape anisotropy of a patterned antidot array on the remanent stripe domain configuration of perforated Weak perpendicular magnetic anisotropy (wPMA) NdCo films with hole size comparable to stripe domain periods
This indicates the uniform orientation of the average in-plane magnetization in the observed region (Fig. 2(a)). This configuration minimizes “rotatable anisotropy”, that in wPMA materials tends to align the stripes with the last saturating field direction.[15]. It is favored by magnetostatic shape anisotropy of the antidot array, since this array direction was found to be an easy axis for in-plane magnetized hexagonal arrays of permalloy antidots.[3]

Summary

INTRODUCTION

Magnetic antidots have often been used to tailor the magnetic properties of extended films:[1,2,3,4,5,6,7,8,9,10,11,12] Depending on hole size and array geometry, they can enhance DW pinning,[2] modify magnetic anisotropy and easy axis direction[3] or, even, create ratchet effects on DW propagation.[4] For magnetic materials with in-plane anisotropy (i.e. magnetization confined to sample plane), magnetostatic effects at hole boundaries create periodic closure domain structures[1,3,5] with enhanced stability by the presence of pairs of half-vortices confined to hole edges.[6] magnetization reversal occurs by the propagation of “composite DWs” that separate regions with different orientations of the closure domain structure relative to the applied field directions, so called “superdomains”.7,8. On a longer length scale, “superdomains” are clearly observed, with average in-plane magnetization along the easy axis directions for in-plane shape anisotropy

EXPERIMENTAL

RESULTS AND DISCUSSION

CONCLUSIONS