Structural and magnetic properties of strongly carbon doped Fe–Co thin films

• Stain induction in FeCo films was verified when appropriate buffer is used.
• Carbon may stabilize a tetragonal strain up to higher thicknesses.
• An anisotropic behavior was induced in the magnetic properties of the system.
• High carbon content leads to the formation of separated Fe–Co grains.

In the framework of the ongoing research for novel rare earth free permanent magnet materials, the alloy Fe–Co–C has attracted interest from theorists, since carbon could induce a magneto-crystalline anisotropy. In this work structural and magnetic properties of strongly doped magnetron sputtered thin films were investigated. Au–Cu buffers on MgO (100) substrates were used in order to promote epitaxial FeCo with 001 orientation. By adding carbon as a third element a tetragonal distortion was observed, according to structural measurements. An anisotropic behavior was induced in the magnetic properties of the system, where the magneto-crystalline anisotropy constant Ku value was estimated in the order of 0.8×106 J/m3f or 3 nm thick Fe–Co(C) magnetic layer.