Positions for Master's theses

Elastic properties in low dimensional quantum systems

The coupling between magnetic and lattice degrees of freedom gives rise to many interesting effects. It can induce multiferroic order with ferroelectric polarisation coupled to the magnetic structure or it can generate dynamic mixed magnon-phonon excitations. Strong magneto-elastic coupling is realized for example in LiCrO2, were the corresponding excitations can be probed by inelastic x-ray scattering. Within this project we propose to investigate the influence of magneto-elastic coupling on the elasticity tensor which will help understanding the underlying mechanism. read more
Contact Person:
Dr. Björn Wehinger (bjorn.wehinger@unige.ch), +41 22 379 6365

Spontaneous magnon decay in non-collinear antiferromagnets

Magnons are generally considered long living quasi particles in pure magnetic systems. However according to new theory, in non-collinear magnets magnons only with short lifetime exists in certain regions of the Brillouin zone. We are looking for experimental evidence for the above theory among Mott insulator compounds. We intend to measure inelastic neutron scattering at ILL and PSI on candidate compounds and model the magnon and phonon spectrum.
Contact Person:
Dr. Sandor Toth (sandor.toth@psi.ch), 056 310 31 23

Geometrical magnetic frustration beyond insulating ionic compounds

Magnetic systems with competing interactions can adopt exotic ground states. A particularly promising class is that of the geometrically frustrated magnets in which unusual spin liquids appear, such as in oxides where magnetic moments form pyrochlore or kagome networks. Phases of correlated magnetic moments that remain disordered can couple to the lattice or to the conduction electrons. We are investigating frustrated magnets where the chemical bonding properties or the conduction state deviate from that of an insulating ionic material. In this Master project we will crystallize such novel frustrated magnets and investigate their physics using both macroscopic and neutron diffraction measurements.
Contact Persons:
Dr. Romain Sibille (romain.sibille@psi.ch), 056 310 35 80
Dr. Tom Fennell (tom.fennell@psi.ch), 056 310 32 13

Magnetic order in the anisotropic triangular materials Cs2-xRbxCuBr4

The new mixed system Cs2-xRbxCuBr4 is a model-anisotropic triangular lattice material to study the effects of quenched disorder in frustrated systems. We are interested in controlling frustration in the triangular layer and exploring by continuous tuning within the isotropic or isolated chain limits. During the master thesis the candidate will conduct synthesis of the new material and its characterization using different techniques (including neutron scattering).
Contact Persons:
Dr. Natalija van Well (natalija.van-well@psi.ch), 056 310 33 87
Dr. Emmanuel Canevet (emmanuel.canevet@psi.ch), 056 310 36 40
Dr. Oksana Zaharko (oksana.zaharko@psi.ch), 056 310 46 33

Magnetic structure in the ordered phase of Cs3Cu3Cl8OH with quantum trimer lattice

Many systems presenting connected triangular motifs have been extensively studied (for example the corner sharing kagomé lattice), but very few model materials with weakly connected triangles have been investigated. The recently discovered compound Cs3Cu3Cl8OH is a model material to study such quantum trimer physics. During the master thesis the candidate will conduct the synthesis of the new material (also doping with Br) and the characterization using different techniques (including neutron scattering).
Contact Persons:
Dr. Natalija van Well (natalija.van-well@psi.ch), 056 310 33 87
Dr. Emmanuel Canevet (emmanuel.canevet@psi.ch), 056 310 36 40
Dr. Oksana Zaharko (oksana.zaharko@psi.ch), 056 310 46 33