SKM 2023 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 50: Focus Session: Superconducting Nickelates II
TT 50.6: Vortrag
Donnerstag, 30. März 2023, 16:15–16:30, HSZ 03
Magnetic interactions in InNiO3 compared to RNiO3 — •Alexander Yaresko, Graham McNally, Minu Kim, and Hidenori Takagi — Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany
RNiO3 nikelates undergo with lowering temperature a metal-to-insulator (MIT) transition, accompanied by orthorhombic-to-monoclinic distortion of their crystal structure, and another transition at TN to a magnetically ordered state with the ordering vector q=(1/2,0,1/2). Two Ni sites in the monoclinic unit cell are nonequivalent, with the average Ni1–O distance being significantly larger than Ni2–O. In compounds with the large radius of a R3+ ion the two transitions occur simultaneously. As the R size decreases, the crystal structure becomes more distorted. As a consequence, the MIT temperature increases while TN decreases. Recently, a new InNiO3 compound, in which an In3+ ion is even smaller than the smallest rare-earth Lu3+, has been synthesized. We performed DFT(+U) calculations for InNiO3 and compare the results to other nikelates. In order to quantify the effect of structural distortions on the magnetic properties we estimated exchange interactions between magnetic Ni1 ions by mapping the energies of spin-spirals with different wave vectors q to an effective Heisenberg model. We found that the strongest interactions are those along Ni1-O-Ni2-O-Ni1 bonds but their strength decreases with increasing lattice distortions. The experimental q=(1/2,0,1/2) order can only be reproduced if a sufficiently small value of Coulomb repulsion U is used for more covalent Ni2 ion.