Anisotropy of linear thermal expansion and compressibility of Y₂Fe₁₇ under pressure and its correlation to magnetic structure

A complex temperature dependence of a.c. susceptibility of Y₂Fe₁₇ under high pressures together with recent neutron diffraction studies under pressure proved the instability of the collinear ferromagnetic structure and the development of a non-collinear magnetic arrangement of Fe moments in Y₂Fe₁₇. To study the correlation between magnetic structure and volume in more detail we performed compressibility and linear thermal expansion studies under high pressures up to 100 kbar and 10 kbar, respectively. The compressibility in the paramagnetic state κ_p (above 10 kbar at room temperature) was determined from the Murnaghan equation of state using the X-ray data, κ_p = 0.80 Mbar^-1. The linear thermal expansion and compressibility in the ferromagnetic state at low temperatures are highly anisotropic. As a consequence, the c/a ratio decreases with increasing pressure. The magnetic phase diagram of Y₂Fe₁₇ compound was compiled up to 20 kbar.