Synthesis of hard magnetic Mn3Ga micro-islands by e-beam evaporation

The permanent magnet industry heavily depends on Nd-Fe-B and Sm-Co alloys because of their high-energy product and high room temperature coercivity. Main ingredient for having such superior magnetic properties compared to other known ferromagnetic materials is rare earth elements (Nd, Sm, Dy. . .). However recent worldwide reserve and export limitation problem of rare earths, shifted researchers' focus to rare earth free permanent magnets. Among many alternatives (FePt, Zr2Co11, FeNi. . .), Mn-based alloys are the most suitable due to abundance of the forming elements and trivial formation of the necessary hard phases. In this study, Mn3Ga micro islands have been prepared. Mn3Ga owes its hard magnetic properties to tetragonal D0(22) phase with magnetic anisotropy energy of 2 MJ/m(3). Thin films and islands of Cr/MnGa/Cr layers have been deposited on Si/SiO2 wafers using combination of e-beam and thermal evaporation techniques. Cr has been used as buffer and cover layer to protect the sample from the substrate and prevent oxidation during annealing. Annealing under Ar/H-2 forming gas has been performed at 350 degrees C for 10 min. Nano thick islands of 25, 50 and 100 mu m lateral size have been produced by photolithography technique. Room temperature coercivity of 7.5 kOe has been achieved on 100 mu m micro islands of Mn3Ga. Produced micro islands could be a rare earth free alternative for magnetic memory and MEMS applications. (C) 2017 Author(s).