Re-entrant magneto-elastic transition in HoFe4Ge2: an XRPD study

Abstract High-quality powder XRD data collected on the ESRF beam line BM16, are presented for the entire magnetically ordered regime ( T N =50 K) of the compound HoFe4Ge2. The data analysis reveals the occurrence of a re-entrant structural transition. The first symmetry breaking transition is of second order and occurs at the magnetic transition while the second transition occurs at lower temperatures at 15 K and is of first order: P 4 2 / mnm (T c ,T N =50 K )→ Cmmm (T IC =15 K )→ P 4 2 / mnm. The phase diagram comprises three temperature regions: (a) the high temperature range with T>TN for the tetragonal P42/mnm phase; (b) the intermediate temperature range, 15 K