Magnetic properties of La doped rare earth permanent magnets

Abstract

Powerful permanent magnets are a crucial component in electric motors and gen- erators,while the most powerful magnets available nowadays are alloys of rare-earth (RE) elementslike Nd or Dy and magnetic transition metal (TM) elements like Fe or Co. Unfortunately, theavailability of the RE elements of the best magnets is strongly limited while they becamerather expensive in production. Therefore, different paths are undertaken in order to findbetter or cheaper permanent magnets. We study com- putationally the effect of La doping onthe magnetic properties of permanent magnet.The major physical properties under consideration are the coercive field strength, themagnetization, and the Curie temperature. In terms of computation methods, we are looking forthe magnetic moments, the magnetic coupling, the magnetic anisotropy and the Curietemperature. These quantities and their dependence on the doping have to be at first betterunderstood and in a second step optimized for a good performance of the magnets.We use a multi-code approach for the theoretical investigation utilizing the Korringa- Kohn-Rostoker method, the Vienna ab initio simulation package (VASP) and Open source packagefor Material eXplorer (OpenMX). We found significant changes in the calculated magneticproperties when mixing La with RE. Looking at the formation energy of the compoundsidentifies possible stable concentration regimes where new compounds could be synthesized.