Two types of magnetic shape-memory effects from twinned microstructure and magneto-structural coupling in Fe<sub>1+<i>y</i></sub> Te.
basic_science · Level V
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- Record sourced from PubMed, PMID 31391310.
- Also identified by DOI 10.1073/pnas.1905271116 and PMC identifier 6708364.
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Abstract
A detailed experimental investigation of Fe<sub>1+<i>y</i></sub> Te (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 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.