High Pressure Structural and Resistivity Measurements around Magnetic Quantum Critical Points

Strong electron correlations can produce new quantum states which cannot be explained by traditional theories of matter such as Fermi liquid theory. High pressure is a versatile tuning parameter which can sensitively change the electron correlations in materials. It has been found that a rich discovery arena for new quantum ordered states has been in systems which are on the border of long range magnetic order. Pressure can be used to “push” materials into new quantum states in a controlled way by supressing the magnetic ordering temperature and driving the material to a quantum critical point. In particular we have been investigating the inter-relationship between structure, magnetic and electronic properties in a number of heavy Fermion d and f-metal ferromagnets and anti-ferromagnets in high-purity samples. We have used a combination of low noise resistivity experiments and powder synchrotron x‑ray diffraction experiments performed at temperatures down to 15 mK and at high pressures to 20 GPa in diamond anvil cells to investigate the subtle changes in structure, properties and quantum states that occur. The experimental arrangements will be presented and results discussed in relation to the properties of the materials.