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

O Akdogan

doi:10.1063/1.5007666

Abstract

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 D022 phase with magnetic anisotropy energy of 2 MJ/m3. 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/H2 forming gas has been performed at 350oC for 10 min. Nano thick islands of 25, 50 and 100 μm lateral size have been produced by photolithography technique. Room temperature coercivity of 7.5 kOe has been achieved on 100 μm micro islands of Mn3Ga. Produced micro islands could be a rare earth free alternative for magnetic memory and MEMS applications.

Highlights

The tendency to shrink devices we use every day has led researchers to nano/micro structures dominating many applications in our daily lives
The most important development that triggered the investigation of magnetic materials in recent years is export shortages in rare earth metals (Dy, Nd, Sm...).[5]
Compared to the previous works and synthesizing methods; high throughput method of e-beam/thermal evaporation followed by flash annealing has been applied for the first time and led to successful production of high coercivity Mn3Ga micro-magnets

Summary

INTRODUCTION

The tendency to shrink devices we use every day has led researchers to nano/micro structures dominating many applications in our daily lives. According to the requirements of the application, nano/micro-sized magnetic structures; the functionality created by their ability to be controlled by the magnetic field generated by them and/or the external magnetic field, made them indispensable for many applications.[1,2,3]. Successful production of micronsized magnets could open the way to new applications. Mn3Ga micro-magnets production steps and magnetic, structural and morphological properties will be briefly reported. Compared to the previous works and synthesizing methods; high throughput method of e-beam/thermal evaporation followed by flash annealing has been applied for the first time and led to successful production of high coercivity Mn3Ga micro-magnets

EXPERIMENTAL

RESULTS AND DISCUSSIONS

CONCLUSION