Frustrated local-moment models for iron pnictide magnetism

Spin liquids and frustrated magnetism

Local quantum criticality of an iron-pnictide tetrahedron.

Motivated by the close correlation between transition temperature (T(c)) and the tetrahedral bond angle of the As-Fe-As layer observed in the iron-based superconductors, we study the interplay between spin and orbital physics of an isolated iron-arsenide tetrahedron embedded in a metallic environment. Whereas the spin-Kondo effect is suppressed to low temperatures by Hund's coupling, the orbita...

Magnetism of frustrated regular networks

We consider a regular random network where each node has exactly three neighbours. Ising spins at the network nodes interact antiferromagnetically along the links. The clustering coefficient C is tuned from zero to 1/3 by adding new links. At the same time, the density of geometrically frustrated links increases. We calculate the magnetic specific heat, the spin susceptibility and the Edwards-A...

Magnetism of frustrated metallic compound BaVS3

The microscopic magnetism of BaVS3, which undergoes a metal-insulator transition at TMI = 70K, has been investigated by using V nuclear resonance and neutron scattering. At 1.4K, we observed zero-field resonance signals in a low-frequency range, which were interpreted as being NQR, i.e., the absence of a static hyperfine field. On the other hand, we found magnetic Bragg peaks below 30K, indicat...

Aspects of Frustrated Magnetism and Topological Order

In the first part we study O(N) spins on geometrically frustrated pyrochlore and planar pyrochlore lattices. For classical spins the strong frustration causes a lack of ordering for N 6= 2 at all temperatures. Nevertheless at low temperatures the system is strongly correlated. We find degrees of freedom that are relevant in this regime and find that the correlations are dipolar up to distance ∼...