Abstract
Single crystals of novel orthorhombic (space group Pnnm) iron tetraboride were synthesized at pressures above 8 GPa and high temperatures. Magnetic susceptibility and heat capacity measurements demonstrate bulk superconductivity below 2.9 K. The putative isotope effect on the superconducting critical temperature and the analysis of specific heat data indicate that the superconductivity in is likely phonon mediated, which is rare for Fe-based superconductors. The discovered iron tetraboride is highly incompressible and has the nanoindentation hardness of 62(5) GPa; thus, it opens a new class of highly desirable materials combining advanced mechanical properties and superconductivity.
- Received 22 February 2013
DOI:https://doi.org/10.1103/PhysRevLett.111.157002
© 2013 American Physical Society
Viewpoint
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