Native Oxidation and Complex Magnetic Anisotropy‐Dominated Soft Magnetic CoCrFeNi‐Based High‐Entropy Alloy Thin Films

Abstract

Soft magnetic high-entropy alloy thin films (HEATFs) exhibit remarkable freedom of material-structure design and physical-property tailoring, as well as, high cut-off frequencies and outstanding electrical resistivities, making them potential candidates for high-frequency magnetic devices. In this study, a CoCrFeNi film with excellent soft magnetic properties is developed by forming a novel core-shell structure via native oxidation, with ferromagnetic elements Fe, Co, and Ni as the core and the Cr oxide as the shell layer. The core-shell structure enables a high saturation magnetization, enhances the electrical resistivity, and thus reduces the eddy-current loss. For further optimizing the soft magnetic properties, O is deliberately introduced into the HEATFs, and the O-incorporated HEATFs exhibit an electrical resistivity of 237 μ𝛀•cm, a saturation magnetization of 535 emu cm −3 , and a coercivity of 23 A m −1 . The factors that determine the ferromagnetism and coercivity of the CoCrFeNi-based HEATFs are examined in detail by evaluating the microstructures, magnetic domains, chemical valency, and 3D microscopic compositional distributions of the prepared films. These results are anticipated to provide insights into the magnetic behaviors of soft magnetic HEATFs, as well as aid in the construction of a promising material-design strategy for these unique materials.

Theoretical insights into the lattice thermal conductivity and thermal expansion of CoNiFe medium-entropy alloys

“…Medium-entropy alloys (MEAs) [1][2][3] have been attracting the attention of researchers due to their excellent mechanical properties, [4][5][6][7][8] especially the alloy systems based on Al and the fourth row elements Fe, Co, Ni, Cr, Cu, Mn and Ti, and Pd. [9][10][11][12][13][14][15] For example, Lang et al 14 studied and compared the formation and evolution of irradiation-induced defects in CoNiFe alloys and pure Ni using molecular dynamics (MD) simulations.…”