A helium-gas-pressure apparatus with optical-reflectivity detection tested with a spin-transition solid

A low temperature helium pressure cell has been constructed that incorporates optical reflectivity detection and is useful for the study of thermochromic materials. The device was tested up to 1600 bar (0.16 GPa) and down to 10 K. Its performance is illustrated by the results of constant pressure and constant temperature runs for the spin transition solid [Fe(btr)\+v\2\-v\(NCS)\+v\2\-v\.H\+v\2\-v\O. The data establish a consistent pressure - temperature phase diagram. (Original abstract)