The role of surface to bulk ratio on the development of magnetic anisotropy in high Ga content Fe100-xGax thin films

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In this work we show the development of bulk in-plane magnetic anisotropy in high Ga-content (Ga = 28 at. %) Fe_(100-x)Ga_x thin films as the layer thickness increases. This result is in clear contrast with the generally reported decrease of this anisotropy with the film thickness. We propose the interrelation between the enhancement of the Ga-pair correlations and a collinear distortion of the bcc structure within the sample plane as the origin of the magnetic anisotropy. Our results have been obtained by employing a combination of long and local range structural probe techniques with bulk and surface magnetic characterization techniques. The key point shown in this work is that the in-plane structural anisotropy and hence, the magnetic anisotropy, are developed as the layer thickness increases. This fact strongly suggests that the surface to bulk free energy ratio plays a key role in the formation of ordered phases with a distorted bcc cell in Fe_(100-x)Ga_x films with x around 28 at. %. Our work also shows the arising of new phenomena in these high Ga content alloys due to the close correlation between structural and magnetic properties.
© 2018 Elsevier B.V. We thank ‘CAI Difracción de rayos-X’ of UCM for x-ray diffractometry measurements and ‘Instituto of Sistemas Optoelectrónicos y Microtecnología’ (ISOM) for using its facilities. We also want to thank BM25-Spline, the Spanish CRG at ESRF in Grenoble (France) for providing beamtime. This work has been financially supported through the project MAT2015-66888-C3-3-R of the Spanish Ministry of Economy and Competitiveness (MINECO/FEDER) and project PR26/16- 3B-2 of Santander and Universidad Complutense de Madrid.