[Zurück]

Y. Cao, C. Lin, M. Avdeev, K. Taddei, Q. Zhang, Q. Huang, Q. Li, K. Kato, C. Chung Tang, A. Gibbs, W. Wang, J. Deng, J. Chen, H. Zhang, X. Xing, S. Khmelevskyi:
"Ultrawide Temperature Range Super-Invar Behavior of R2(Fe,Co)17 Materials (R= Rare Earth).";
Physical Review Letters, 127 (2021), S. 055501.

Super Invar (SIV), i.e., zero thermal expansion of metallic materials underpinned by magnetic
ordering, is of great practical merit for a wide range of high precision engineering. However, the
relatively narrow temperature window of SIV in most materials restricts its potential applications in many
critical fields. Here, we demonstrate the controlled design of thermal expansion in a family of
R2ðFe; CoÞ17 materials (R ¼ rare Earth). We find that adjusting the Fe-Co content tunes the thermal
expansion behavior and its optimization leads to a record-wide SIV with good cyclic stability from
3-461 K, almost twice the range of currently known SIV. In situ neutron diffraction, Mössbauer spectra
and first-principles calculations reveal the 3d bonding state transition of the Fe-sublattice favors extra
lattice stress upon magnetic ordering. On the other hand, Co content induces a dramatic enhancement of
the internal molecular field, which can be manipulated to achieve "ultrawide" SIV over broad
temperature, composition and magnetic field windows. These findings pave the way for exploiting
thermal-expansion-control engineering and related functional materials.

http://dx.doi.org/10.1103/PhysRevLett.127.055501