Effect of grain size on exchange-biased Heusler alloys

Abstract

We report on an investigation into the effects of grain size of both antiferromagnetic IrMn and ferromagnetic Heusler alloy layers on the magnetic properties of exchange-biased films. IrMn/Co 2 FeSi was grown by a HiTUS sputtering system which allows control of the grain size. We found that small IrMn grains (⩽7 nm) could not generate an exchange bias H ex , while those above 8 nm in size showed H ex between 100 and 200 Oe. H ex showed a minor decrease with increasing Co 2 FeSi grain sizes (up to 15–20 nm) but M s gradually increased. Our results show that sharp interfacial matching is required between 8 and 10 nm IrMn grains and 15 nm Co 2 FeSi grains to exhibit both large H ex and M s for device applications.