Nb6mn1-Xir6+Xb8 (X=0.25): A Ferrimagnetic Boride Containing Planar B-6 Rings Interacting With Ferromagnetic Mn Chains

Discovering new low-dimensional magnetic materials is of paramount importance in spintronics. We report on a new ferrimagnetic (FiM) compound, Nb6Mn1-xIr6+xB8 (x = 0.25), the structure of which contains Mn chains embedded in stacked planar B-6 rings. Its crystal structure, which was determined by combined single-crystal X-ray and neutron diffraction studies, contains three Mn chains (intrachain distance is 3.30 angstrom) building a triangular network with an interchain distance of 9.28 angstrom, indicating stronger intrachain interactions than interchain ones. Density functional theory (DFT) calculations proposed ferrimagnetic ordering for the new phase resulting from three nonequivalent, triangularly arranged ferromagnetic (FM) Mn chains with two in spin-up and one in spin-down. Magnetization measurements confirmed the presence of not only strong FM interactions (high Curie temperature of 250 K) but also weak antiferromagnetic AFM) ones small and negative Weiss constant of -70 K), thus confirming the proposed FiM ordering.