Speaker
Description
The study of condensed matter is often achieved by perturbing the system thus creating a resultant change in material properties that provides an insight into the atomic scale interactions. One such perturbation is pressure. Pressure offers a convenient way to perturb quantum spin liquids and tune quantum phase transitions by altering the atomic positions and thereby the dipolar interactions and ionic orbital overlap. Varying the balance between the magnetic interactions, exchange and dipolar interaction including anisotropic crystal field effects, can lead to the creation of novel states of matter. Pressure can be applied in an isotropic manner, hydrostatically, or via tension or compression, known as uniaxial pressure. While hydrostatic pressure tunes all bond lengths symmetrically, uniaxial pressure allows an assymetric distortion of the crystal lattice. The application of uniaxial pressure for neutron scattering studies of quantum systems is particularly difficult since the neutron scattering signals are often weak and broad in S(Q,ω). We have developed a novel uniaxial pressure cell for the study of quantum magnets by neutron scattering. The cell is particularly suitable for inelastic neutron scattering and polarisation analysis of magnetically diffuse signals. The details of the pressure cell will be outlined with examples from recent experiments on the archetypal frustrated compound, Ho2Ti2O7 (HTO), in which we were able to modify the magnetic interaction parameters enabling an optimisation of the dipolar spin model to HTO.
