Nano-columnar, self-organised NiCrC/a-C:H thin films deposited by magnetron sputtering.

Thin films of NiCr–C were deposited by pulse magnetron sputtering of the NiCr20 alloy cathode in an atmosphere containing a mixture of argon and acetylene. Their structure, chemical composition, and magnetic properties were studied using X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, atomic and magnetic force microscopy, and superconducting quantum interference magnetometry methods. Film amorphisation observed upon increasing carbon content was followed by amorphous carbon segregation. As a result of the self-assembly processes during the coating growth, nanostructures were obtained consisting of metallic columns surrounded in carbon sheaths, with axes parallel to the growth direction. The resulting films exhibited weak ferromagnetism in a direction parallel to the axis of the nanocolumns, while the system's response was superparamagnetic for the direction of magnetisation perpendicular to the nanocolumns. • NiCr–C coatings were deposited by reactive magnetron sputtering of the NiCr20 alloy. • Coatings are crystalline, amorphous or nano-structured depending on the carbon content. • The nano-structured coatings consist of metallic nanocolumns in carbon sheaths. • Foils containing 43 % at. C are ferro- or superparamagnetic depending on the direction. • The spin blocking temperature was determined to be about 115 K. [ABSTRACT FROM AUTHOR]