Dresden 2017 – scientific programme
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MA: Fachverband Magnetismus
MA 21: Correlated Electrons: Frustrated Magnets - Strong Spin-Orbit Coupling 1
MA 21.7: Talk
Tuesday, March 21, 2017, 11:00–11:15, HSZ 304
New pyrochlore iridate In2Ir2O7 stabilised by high pressure — •Aleksandra Krajewska1, 2, Tomohiro Takayama1, 2, Robert Dinnebier2, Alexander Yaresko2, Kenji Ishii3, and Hidenori Takagi1, 2 — 1Institut für Funktionelle Materie und Quantentechnologien, University of Stuttgart, 70550 Stuttgart, Germany — 2Max-Planck Institute for Solid State Research, 70569 Stuttgart, Germany — 3QST, Hyogo 679-5148, Japan
In 5d transition metal oxides Coulomb repulsion, crystal field splitting and spin-orbit coupling are comparable which leads to a variety of exotic electronic states. Pyrochlore iridates with chemical formula A2Ir2O7 (A= Y, rare earth) consist of A and Ir corner-sharing tetrahedral networks and are predicted to exhibit Weyl semimetal or topological insulator states. Their properties depend on the ionic radius of A3+, where the system is driven from metallic to insulating regime with decreasing A3+ size. Those effects are likely related to diverging degree of local lattice distortion. In our work in order to explore small A3+ limit we synthesised new pyrochlore In2Ir2O7 using high pressure. Structural analysis shows its octahedra are the most distorted among A2Ir2O7 family which is in agreement with its insulating behaviour. It shows magnetic order at TN = 55 K with θCW ∼ -400 K, which suggests strong frustration and is in large contrast with Y2Ir2O7 (TN = 155 K, θCW ∼ -130 K). Our band calculation shows that despite large distortion In2Ir2O7 is in proximity to pure jeff = 1/2, unlike Y2Ir2O7, which shows strong hybridisation of jeff = 1/2 and jeff = 3/2. We will discuss the possible origin of almost pure jeff = 1/2 state in In2Ir2O7.