Frustrated Magnets

Besides the magnetic order phenomena like ferro-, ferri-, and antiferromagnetism, the case of magnetic frustration is a widely investigated research topic positioned at the boundaries between materials science and theoretical physics. Very recently, some frustrated magnets became interesting not only from a scientific viewpoint, but also as potential materials for technological applications in novel magnetic refrigerators.

In a frustrated magnet the magnetic exchange interactions among the different spins cannot all be satisfied. The classic example for a frustrated magnet is the simple triangular arrangement of Ising-spins, in which antiferromagnetic interactions account for spin frustration. The interplay between geometric frustration and spin ordering leads to a multidegeneracy of the ground states.
We are currently working on two frustrated magnets, the rubidium sesquioxide Rb₄O₆, which exhibits a non-collinear spin configuration and a series of frustrated tetragonal ferrimagnets Mn_3-xGa, which are promising candidates for spin torque transfer applications.

References:

Challenging the prediction that rubidium sesquioxide Rb₄O₆ is an anionogenic ferromagnet, J. Winterlik, G. H. Fecher, C. Felser, C. Mühle and M. Jansen, JACS 129 (2007) 6990.

Mn₃Ga, a compensated ferrimagnet with high Curie temperature and low magnetic moment for spin torque transfer applications, B. Balke, G. H. Fecher, J. Winterlik and C. Felser, Appl. Phys. Lett. 90 (2007) 152504.

Structural, electronic and magnetic properties of tetragonal Mn_3-xGa: Experiments and first-principles calculations, J. Winterlik, B. Balke, G. H. Fecher and C. Felser, M. C. M. Alves, F. Bernardi and J. Morais, accepted Phys. Rev. B (2008).