Increased magnetocrystalline anisotropy in epitaxial Fe-Co-C thin films with spontaneous strain

Abstract

Rare earth free alloys are in focus of permanent magnet research since the accessibility of the elements needed for nowadays conventional magnets is limited. Tetragonally strained iron-cobalt (Fe-Co) has attracted large interest as promising candidate due to theoretical calculations. In experiments, however, the applied strain quickly relaxes with increasing film thickness and hampers stabilization of a strong magnetocrystalline anisotropy. In our study we show that already 2 at% of carbon substantially reduce the lattice relaxation leading to the formation of a spontaneously strained phase with 3 % tetragonal distortion. In these strained (Fe${}_{0.4}$Co${}_{0.6}$)${}_{0.98}$C${}_{0.02}$ films, a magnetocrystalline anisotropy above 0.4 MJ/m${}^3$ is observed while the large polarization of 2.1 T is maintained. Compared to binary Fe-Co this is a remarkable improvement of the intrinsic magnetic properties. In this paper, we relate our experimental work to theoretical studies of strained Fe-Co-C and find a very good agreement.

19 pages, 6 figures

References in corpus (1)

• Magnetic anisotropy energy of disordered tetragonal Fe-Co systems from ab initio alloy theory

Cited by in corpus (4)

• Heteroepitaxial growth of tetragonal Mn${}_{2.7-x}$Fe${}_x$Ga${}_{1.3}$ (0 $⩽$ x $⩽$ 1.2) Heusler films with perpendicular magnetic anisotropy
• Structural and magnetic properties of Fe-Co-C alloys with tetragonal deformation: a first-principle study
• On the origin of perpendicular magnetic anisotropy in strained Fe-Co(-X) films
• Coulomb correlations and magnetic properties of L1${}_0$ FeCo: a DFT+DMFT study