Investigation of frustrated one-dimensional antiferromagnetic quantum chain systems and the rare earth intermetallic compound TmGa3

My thesis concerns two areas of current research in magnetism, with the common experimental technique of elastic and inelastic neutron scattering on powders and single crystals. The first topic is concerned with rare earth intermetallic compounds with unfilled 4f shells. When a rare earth element with an unfilled shell is placed in an environment with surrounding charges, the crystal electric field acts to lift the J-fold degeneracy. Determination of the Crystal Electric Field (CEF) ground state and excited states are important to understand the complex and interesting low temperature phase diagrams these compounds exhibit. This will be discussed for the rare earth intermetallic compound TmGa3. The other area of my thesis concerns one dimensional Heisenberg antiferromagnetic quantum chains systems. Due to the one-dimensional lattice and low spin, quantum fluctuations play an important role in these systems. From the nature of the lattice, the interactions could give rise to magnetic frustration, resulting in interesting ground states. I will discuss results on the binary halides CuCl2, CuBr2 and on the quaternary oxide LiCuVO4. To measure the thermal properties of the investigated systems, a quasi-adiabatic Nernst type calorimeter was constructed and commissioned. I will describe the design and the properties of the calorimeter.