Using combinatorial sputtering to uncover new magnetic high entropy alloys

The search for new magnetic thin films has been accelerated by the development of high-throughput fabrication using combinatorial sputtering followed by high-throughput characterization methods including x-ray diffraction, scanning electron microscopy, and magneto-optic Kerr effect magnetometry. From the compositional-property plot obtained from these measurements, down-selection of the most promising compositions for further in-depth studies can be carried out. This paper studies two different thin magnetic film systems with the compositions CoFeNiMn–X, where X is Al or Si. For each film system, the composition of each element ranges between 10 and 40 at. %, allowing for a wide selection of different compositions to be studied. Focusing on soft magnetic properties, the compositions down-selected are further characterized using SQUID magnetometry to determine the saturation magnetization and coercive field. This paper shows that, for combinatorially grown CoFeNiMn–Al films over a wide composition range, the main phase was BCC. When comparing the saturation magnetization measured for different CoFeNiMn–Al compositions from the combinatorial wafer, with those in the literature for single composition films, there was good agreement between them. For the CoFeNiMn–Si films, when the ratio of the elements was roughly equimolar, the composition was magnetic, with the XRD showing an amorphous phase and possible intermetallic phases. While reducing the Co, Fe, and Ni concentrations with respect to Mn and Si, the films were nonmagnetic and amorphous.