Unexpected Synergy between Magnetic Iron Chains and Stacked B6 Rings in Nb6Fe1−xIr6+xB8.

The synergistic combination of experiment and density functional theory has led to the discovery of the first ferromagnetic material, Nb₆Fe_1−xIr_{6+ x}B₈, containing in its crystal structure iron chains embedded in stacked B₆ rings. The strong ferromagnetic Fe-Fe interactions found in the iron chains induce an unexpected strengthening of the B-B interactions in the B₆ rings. Beside these strong B-B interactions, strong interlayer metal-boron bonds (Ir-B and Nb-B) ensure the overall structural stability of this phase, while the magnetic Fe-Fe interactions are mainly responsible for the observed ferromagnetic ordering below T_C=350 K. [ABSTRACT FROM AUTHOR]