The first-order structural phase transition at low-temperature in GaPtP and its rapid enhancement with pressure
arXiv:2406.06291
Abstract
Single crystals of XPtP (X = Al, Ga, and In) were grown from a Pt-P solution at high temperatures, and ambient-pressure measurements of temperature-dependent magnetization, resistivity, and X-ray diffraction were made. Also, the ambient-pressure Hall resistivity and temperature-dependent resistance under pressure were measured on GaPtP. All three compounds have tetragonal crystal structure at room-temperature with metallic transport and weak diamagnetism over the ~K temperature range. Surprisingly, at ambient pressure, both the transport and magnetization measurements on GaPtP show a step-like feature in ~K region suggesting a possible structural phase transition, and no such features were observed in (Al/In)PtP. Both the hysteretic nature and sharpness of the feature suggest the first-order transition, and single-crystal X-ray diffraction measurements provided further details of the structural transition with a crystal symmetry likely different than below transition. The transition is characterized by anisotropic changes in the lattice parameters, a volume collapse, and satellite peaks at two distinct wave-vectors. Density functional theory calculations present phonon softening as a possible driving mechanism. Additionally, the structural transition temperature increases rapidly with increasing pressure, reaching room temperature by ~GPa, highlighting the high degree of pressure sensitivity and fragile nature of GaPtP room-temperature structure. Although the volume collapse and extreme pressure sensitivity suggest chemical pressure should drive a similar structural change in AlPtP, with smaller unit cell dimensions and volume, its structure is found to be as well. Overall, GaPtP stands out as a sole member of the 1-5-1 family of compounds with a temperature-driven structural change.
18 pages, 19 figures