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Spin Frustration and Magnetic Ordering from One-Dimensional Stacking of Cr3 Triangles in TiCrIr2B2

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posted on 16.05.2016, 18:53 by Michael Küpers, Laura Lutz-Kappelman, Yuemei Zhang, Gordon J. Miller, Boniface P. T. Fokwa
Spin-frustrated chains of Cr3 triangles are found in the new metal boride TiCrIr2B2 by synergistic experimental and theoretical investigations. Although magnetic ordering is found at 275 K, competing ferro- and anti-ferromagnetic interactions coupled with spin frustration induce a rather small total magnetic moment (0.05 μB at 5 T), and density functional theory (DFT) calculations propose a canted, nonlinear magnetic ground-state ordering in the new phase. TiCrIr2B2 crystallizes in the hexagonal Ti1+xOs2–xRuB2 structure type (space group P6̅2m, No. 189, Pearson symbol hP18). The structure contains trigonal planar B4 boron fragments with B–B distances of 1.76(3) Å alternating along the c-direction with Cr3 triangles with intra- and intertriangle Cr–Cr distances of 2.642(9) and 3.185(1) Å, respectively. Magnetization measurements of TiCrIr2B2 reveal ferrimagnetic behavior and a large, negative Weiss constant of −750 K. DFT calculations demonstrate a strong site preference of Cr for the triangle sites, as well as magnetic frustration due to indirect anti-ferromagnetic interactions within the Cr3 triangles.