Investigation of artificial domains realised by local gallium focused ion beam (FIB) modification of Pt/Co/Pt trilayer structures

TL;DR

This study explores how local gallium FIB modification creates artificial magnetic domains in Pt/Co/Pt trilayers, enabling control over domain size and reversal dynamics, with potential implications for magnetic device engineering.

Contribution

It demonstrates a novel method to pattern artificial magnetic domains using gallium FIB, revealing size-dependent coercivity and domain wall resistance in Pt/Co/Pt structures.

Findings

Artificial domains with sub-micron widths were created.

Reversal occurs via large Barkhausen events in minor loops.

Domain wall resistance remains positive from 4.2 K to 300 K.

Abstract

We present the results of experimental investigations of magnetic switching and magnetotransport in a new generation of magnetic devices containing artificially patterned domains. Our devices are realised by locally reducing the coercive field of a perpendicularly magnetised Pt (3.5 nm)/Co (0.5 nm)/Pt (1.6 nm) trilayer structure using a gallium focused ion beam (FIB). Artificial domain walls are created at the interfaces between dosed and undosed regions when an external magnetic field switches the former but not the latter. We have exploited this property to create stripe-like domains with widths down to sub-micron lengthscales, separated by undosed regions. Using the extraordinary Hall effect to monitor the local magnetisation we have investigated the reversal dynamics of these artificial domains by measuring major and minor hysteresis loops. The coercive field of regions irradiated with identical doses systematically increases as their size decreases. In the lower branch of minor loops, reversal is seen to occur via a few large Barkhausen events. Preliminary measurements of transport across domain walls reveal a positive domain wall resistance, that does not change sign from 4.2 K to 300 K.