Two types of magnetic shape-memory effects from twinned microstructure and magneto-structural coupling in Fe1+yTe

Sahana Rößler, Cevriye Koz, Zhaosheng Wang, Yurii Skourski, Mathias Doerr, Deepa Kasinathan, Helge Rosner, Marcus Schmidt, Ulrich Schwarz, Ulrich K. Rößler, Steffen Wirth
2019 Proceedings of the National Academy of Sciences of the United States of America  
A detailed experimental investigation of Fe1+yTe (y = 0.11, 0.12) using pulsed magnetic fields up to 60 T confirms remarkable magnetic shape-memory (MSM) effects. These effects result from magnetoelastic transformation processes in the low-temperature antiferromagnetic state of these materials. The observation of modulated and finely twinned microstructure at the nanoscale through scanning tunneling microscopy establishes a behavior similar to that of thermoelastic martensite. We identified the
more » ... observed, elegant hierarchical twinning pattern of monoclinic crystallographic domains as an ideal realization of crossing twin bands. The antiferromagnetism of the monoclinic ground state allows for a magnetic-field–induced reorientation of these twin variants by the motion of one type of twin boundaries. At sufficiently high magnetic fields, we observed a second isothermal transformation process with large hysteresis for different directions of applied field. This gives rise to a second MSM effect caused by a phase transition back to the field-polarized tetragonal lattice state.
doi:10.1073/pnas.1905271116 fatcat:dfscps5wibgsznlsgcj7ozp5ru