Helium ion beam milling to create a nano-structured domain wall magnetoresistance spin valve

Yudong Wang*, S. A. Boden, D. M. Bagnall, H. N. Rutt, C. H. de Groot

*Corresponding author for this work

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

We have fabricated and measured single domain wall magnetoresistance devices with sub-20nm gap widths using a novel combination of electron beam lithography and helium ion beam milling. The measurement wires and external profile of the spin valve are fabricated by electron beam lithography and lift-off. The critical bridge structure is created using helium ion beam milling, enabling the formation of a thinner gap (and so a narrower domain wall) than that which is possible with electron beam techniques alone. Four-point probe resistance measurements and scanning electron microscopy are used to characterize the milled structures and optimize the He ion dose. Successful operation of the device as a spin valve is demonstrated, with a 0.2% resistance change as the external magnetic field is cycled. The helium ion beam milling efficiency as extracted from electrical resistance measurements is 0.044atoms/ion, about half the theoretical value. The gap in the device is limited to a maximum of 20nm with this technique due to sub-surface swelling caused by injected ions which can induce catastrophic failure in the device. The fine patterning capabilities of the helium ion microscope milling technique indicate that sub-5nm constriction widths could be possible.

Original languageEnglish
Article number395302
Pages (from-to)1-8
Number of pages8
JournalNanotechnology
Volume23
Issue number39
DOIs
Publication statusPublished - 2012
Externally publishedYes

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