First-order structural transition in the magnetically ordered phase of Fe1.13Te

TL;DR

This study investigates the phase transitions in Fe1.13Te, revealing a first-order structural transition that occurs after magnetic ordering, with detailed measurements showing the sequence and nature of these transitions.

Contribution

It provides new insights into the sequence and character of magnetic and structural transitions in Fe1.13Te, highlighting differences from Fe pnictides.

Findings

Magnetic transition at T_N precedes structural transition at T_s.

Structural transition coincides with change in magnetic structure.

Lattice symmetry changes only below T_s.

Abstract

Specific heat, resistivity, magnetic susceptibility, linear thermal expansion (LTE), and high-resolution synchrotron X-ray powder diffraction investigations of single crystals Fe1+yTe (0.06 < y < 0.15) reveal a splitting of a single, first-order transition for y < 0.11 into two transitions for y > 0.12. Most strikingly, all measurements on identical samples Fe1.13Te consistently indicate that, upon cooling, the magnetic transition at T_N precedes the first-order structural transition at a lower temperature T_s. The structural transition in turn coincides with a change in the character of the magnetic structure. The LTE measurements along the crystallographic c-axis displays a small distortion close to T_N due to a lattice striction as a consequence of magnetic ordering, and a much larger change at T_s. The lattice symmetry changes, however, only below T_s as indicated by powder X-ray diffraction. This behavior is in stark contrast to the sequence in which the phase transitions occur in Fe pnictides.