Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 30: Correlated Electrons: Spin Systems and Itinerant Magnets – Frustrated Magnets 3 (jointly with MA)

TT 30.12: Talk

Tuesday, March 17, 2015, 12:30–12:45, H 0110

Anisotropic Ru³⁺ - 4d⁵ - magnetism in the α-RuCl₃ honeycomb system: susceptibility, specific heat and Zero field NMR — •Michael Baenitz¹, Mayukh Majumder¹, Helge Rosner¹, Alexander Tsirlin², Hiroshi Yasuoka¹, and Markus Schmidt¹ — ¹MPI for the Chemical Physics of Solids, 01187 Dresden, Germany — ²National Institute of Chemical Physics and Biophysics, Tallinn, Estonia

Low dimensional 4d- and 5d-magnets show a wide variety of magnetic ground states due to crystal electric field (CEF) splitting and strong spin-orbit coupling (SOC). The Heisenberg-Kitaev model was applied for the competing bond-dependent magnetic exchange interactions in the 5d-honeycomb lattices (Li₂IrO₃, Na₂IrO₃). α-RuCl₃ turns out to be an excellent candidate for that model because the low-spin 3+ state of Ru (4d⁵) is equivalent to the low-spin 4+ state of Ir (5d⁵). Hexagonal α-Ru trichloride single crystals exhibit a strong magnetic anisotropy and we show that upon applying fields up to 14 T in the honeycomb plane the successive magnetic order at T₁ = 14 K and T₂ = 8 K could be completely suppressed whereas in the perpendicular direction the magnetic order is robust. Furthermore the field dependence of χ(T) implies coexisting ferro- and antiferromagnetic exchange between in-plane components of Ru³⁺-spins, whereas for out-of-plane components a strong antiferromagnetic exchange becomes evident. ¹⁰¹Ru zero-field nuclear magnetic resonance evidence a complex (probably chiral) long-range magnetic order below 14 K. The large orbital moment on Ru³⁺ is found in density-functional calculations.