Diffuse reflectance is a powerful optical technique to study powder samples. A home-made set-up has been built up in order to perform measurement as a function of temperature (77K – 400K) and/or pressure (up to 10 kbar). The set-up is based on Y-shape optical fiber bundle. One branch of the bundle is used to excite the sample while the other two branches collect the diffused light. This latter is analyzed by a photodiode and an Ocean Optics spectrometer (200 nm – 1100 nm). The sample is placed in a nitrogen cooled cryostat. Hydrostatic pressure is applied through helium or nitrogen gas.

Thermal and pressure hysteresis loops recorded on a spin crossover compound.