Magnetic properties of hard-soft MnBi/FeNi@C exchange coupled nanostructures via cryo-milling

The extremely important permanent magnets encounter uncertainty and cost variations due to utilization of rare earths as prime components. Hence, the exchange coupled magnets comprised of hard and soft magnets in different proportions are explored to optimize the magnetic properties and cost. In this line, we prepared exchange coupled magnets of MnBi with FeNi@C nanoparticles (varying compositions = 10, 15 and 20 wt %) via cryogenic ball milling route. Out of these, the nanocomposite with MnBi and 15 wt% FeNi@C provided a coercivity value of 7.9 kOe with saturation magnetization and remanance values of 63 and 38 emu/g respectively. This exchange coupled magnet shown improvement in the MS, S , HC C and Mr r values by 53, 18 and 90 % respectively as compared to MnBi alone. The carbon layer over FeNi@C phase (MS = 147 emu/g) as well as cryomilling facilitated the formation of its exchange coupled magnet with MnBi.