Thickness-Driven Magnetic Behavior in Ni-Cr Nanocrystalline Thin Films: Implications for Spintronics and Magnetic Cooling

Alloying antiferromagnetic Cr with ferromagnetic Ni forms an excellent starting point to design materials for various room temperature applications, such as spintronics, the magnetocaloric effect, and hyperthermia, thanks to its tunable Curie temperature, T-C, and competing magnetic interactions. In this report, we present a comprehensive analysis of the relationships among film thickness, Cr surface segregation, and magnetic properties in nanocrystalline Ni100-xCrx (x = 5-15 at. %) thin films. We assess the impact of Cr segregation evolution on various magnetic transitions as the thickness and Cr doping level increase. These films exhibited ferromagnetic to paramagnetic transitions at higher temperatures and ferromagnetic to spin-glass transitions at low temperatures, which resulted in a phase diagram that differed from the bulk equilibrium phase diagram. Further, magnetometry and magnetic force microscopy were performed to investigate the magnetic anisotropy and magnetic domain structure as a function of film thickness. It is found that the perpendicular component of magnetic anisotropy (Q = K-p/(2 pi M-s(2)) approximate to 0.5)= 2 led to a stripe domain structure in films with critical thicknesses above 20 nm. Substantial changes in the magnetization behavior of nanocrystalline Ni100-xCrx thin films within a few Cr at. % doping provide a means for adjusting both soft and hard magnetic component applications.

Automated summary

Alloying antiferromagnetic Cr with ferromagnetic Ni enables the design of materials for room temperature applications with adjustable Curie temperature and magnetic interactions. This study investigates the relationship between film thickness, Cr surface segregation, and magnetic properties in nanocrystalline Ni100-xCrx thin films. The results show that the magnetic transitions and domain structure are influenced by Cr segregation evolution and film thickness. The behavior of the nanocrystalline Ni100-xCrx thin films can be adjusted by controlling the Cr doping level, providing a means for diverse magnetic applications.