Tuesday next week (21/5) we are visited by Professor Olav Syljuåsen from the University of Oslo. Olav is an expert in simulations of spin systems and is presently on a sabbatical at U. Cph.

He will give a presentation on spiral states of classical spins on a pyrochlore lattice at **11.00 in B311/001 (Building 311, ground floor)**.

**Abstract**

The classical nearest-neighbor Heisenberg antiferromagnet on the pyrochlore lattice is a spin liquid. However, when adding small further-neighbor interactions this behavior gives way to ordered states. In this talk I will argue that, for a certain kind of further-neighbor interaction, the ordering pattern will be that of “double spirals” where pairs of sublattices form antiparallel spirals. The spiral ordering wave vectors of the two pairs are in general different from each other and are constrained by which sublattices are being paired. I will also present the phase diagram and discuss the effect of a magnetic field.