Discovery of a Superhard Iron Tetraboride Superconductor

• DOI: 10.1103/physrevlett.111.157002
• Publication Date: 2013-10-09T15:27:34Z
• Authors: Huiyang Gou; Natalia Dubrovins...; Elena Bykova; Alexander A. Tsirlin; Deepa Kasinathan; Walter Schnelle; Asta Richter; Marco Merlini; Michael Hanfland; Artem M. Abakumov; Dmitry Batuk; Gustaaf Van Tendeloo; Yoichi Nakajima; Aleksey N. Kolmog...; Leonid Dubrovinsky
• Keywords: Condensed Matter - Materials Science; Materials Science (cond-mat.mtrl-sci); FOS: Physical sciences; 02 engineering and technology; 0210 nano-technology; 01 natural sciences; 0104 chemical sciences

Single crystals of novel orthorhombic (space group Pnnm) iron tetraboride FeB4 were synthesised at pressures above 8 GPa and high temperatures. Magnetic susceptibility measurements demonstrated bulk superconductivity below 2.9 K. The putative isotope effect on the superconducting critical temperature indicates that FeB4 is likely a phonon-mediated superconductor, which is unexpected in the light of previous knowledge on Fe-based superconductors. The discovered iron tetraboride is highly incompressible and has the nanoindentation hardness of 65(5) GPa, thus, it opens a new class of highly desirable materials combining advanced mechanical properties and superconductivity.<br/>7 pages<br/>