Phase Transition to Modulated Cubic Phase in AuZn alloy

AuZn is believed to undergo a martensitic transition from a high-temperature cubic phase to a reported low-temperature trigonal phase around 60K. Specific heat studies revealed that the transition is second-order for the 50-50 alloy, and first-order for off-stoichiometric compositions. Elastic neutron diffraction studies on a single crystal of the 50-50 alloy showed the surprising result that the martensitic transformation is suppressed and new Bragg peaks appear at q$_{o }$= (1/3,1/3,0), in a continuous manner. The low-temperature structure can be viewed as cubic with a 3-fold increase in the cell along the [110] direction, similar to what has been observed in premartensitic phases. Attempts to measure the phonon dispersion curves using inelastic x-ray scattering will also be discussed.