Determining the magnetic structures of rare earth compounds

Program Code: 
1892
Contact: 

Prof Sean Cadogan (s.cadogan@adfa.edu.au)

Description of Work: 

Objectives:

Rare earth intermetallic compounds are important from both theoretical and applied points of view. The magnetic structures adopted in these compounds allow us to probe the fundamental magnetic exchange and crystal-field interactions across a series of related compounds. Such compounds are also the basis for the World’s strongest permanent magnets and they underpin the coming generation of magnetic refrigeration materials. The aim of our research is to investigate the interplay between the crystallography and the aforementioned fundamental interactions as these lie at the heart of the intrinsic magnetic behaviour of rare-earth compounds.

In this project we will prepare a number of series of intermetallic compounds containing rare-earth elements and study their crystallography and magnetism using a variety of experimental techniques (x-ray and neutron diffraction, Mössbauer Spectroscopy, Magnetometry etc). We will determine the magnetic structures of these compounds and we will investigate the changes in magnetic structure that often occur when one cools the sample. Such changes are usually the result of competition between different terms in the crystal-field interaction and this project offers the scope for computer modelling of the intrinsic magnetic behaviour of a rareearth compound.

Description of Work:

  • Preparation of compounds by argon-arc melting and annealing, with characterisation by standard techniques such as x-ray diffraction;
  • Carry out basic measurements of a compound’s magnetic properties using magnetometry and ac-susceptibility;
  • Determine the magnetic structures and their temperature evolutions by neutron diffraction and Mössbauer Spectroscopy;
  • Explanation of the magnetic structural behaviour in terms of exchange and crystal-fields.