Interfacial coupling effect of CrO on the magnetic properties of FeGa thin films.

Here it is investigated the effect of the antiferromagnet CrO on the magnetic properties of ferromagnetic FeGa thin films. Sputtered FeGa layers have their magnetization in the sample plane with a magnetic fluctuation that gives rise to magnetic ripple. In order to turn its magnetization into the out of plane (OOP) direction, it has been magnetically coupled with CrO that has magnetic moments along the c-axis, that is the perpendicular direction when properly aligned. CrO has been obtained from Cr oxidation, whereas FeGa has been deposited on top of it by sputtering in the ballistic regime. Although a uniaxial in-plane magnetic anisotropy is expected for FeGa thickness above 100 nm, the interfacial coupling with CrO prevents this anisotropy. The formation of stripe domains in FeGa above a critical thickness reveals the enhancement of the out of plane component of the FeGa magnetization with respect to uncoupled layers. Due to the interface coupling, the FeGa magnetization turns into the out-of-plane direction as its thickness is gradually reduced, and a perpendicular magnetic anisotropy of 3·10 erg·cm is inferred from experimental results. Eventually, the coupling between CrO and FeGa promotes an exchange-bias effect that has been well fitted by means of the random field model.