Magnetostructural phase transitions of DyFe4Ge2: Part I—By XRPD

Abstract: We present the temperature phase diagram of the compound DyFe4Ge2 determined from high-quality powder XRPD for the entire magnetically ordered regime. DyFe4Ge2 undergoes at , a simultaneous structural and magnetic transition of second-order P42/mnm, , , followed by two subsequent isostructural first-order magnetic transitions at and . The structural transition at , is characterised by strong changes of the ratio and of the shear strain while the transition is related to a lattice expansion along on cooling. Minor Fe parameter shifts and deformations (torsion angle and out-of plane Fe–Fe distances) of the Fe tetrahedra were found to accompany the two magnetic transitions. Using the XRPD instrumental resolution and modelling the anisotropic micro-strain enabled us to refine the observed anisotropic peak broadening associated with the presence of micro-structure effects. The maximum strain experienced by the crystal lattice during a sequence of subtle magnetic transitions was observed in the intermediate temperature interval of incommensurate magnetic phases. [Copyright &y& Elsevier]