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TT: Fachverband Tiefe Temperaturen

TT 42: Correlated Electrons: Frustrated Magnets - Cu-based Systems & FeCr

TT 42.4: Talk

Wednesday, March 9, 2016, 10:15–10:30, H18

Spin model of volborthite Cu₃V₂O₇(OH)₂·2H₂O revisited: coupled trimers instead of zigzag chains — •Oleg Janson¹, Shunsuke Furukawa², Tsutomu Momoi^{3, 4}, Philippe Sindzingre⁵, Johannes Richter⁶, and Karsten Held¹ — ¹IFP, TU Wien, Austria — ²University of Tokyo, Japan — ³Condensed Matter Theory Laboratory, RIKEN, Japan — ⁴RIKEN Center for Emergent Material Science, Japan — ⁵Université Pierre & Marie Curie, Paris, France — ⁶University of Magdeburg, Germany

Motivated by recent experiments on volborthite single crystals showing a wide 1/3-magnetization plateau [1], we adopt the structural data and perform microscopic modeling by means of density functional theory (DFT). Using DFT+U, we find four leading magnetic exchanges: antiferromagnetic J and J₂, as well as ferromagnetic J′ and J₁. Simulations of the spin Hamiltonian show good agreement with the experiment for J:J′:J₁:J₂ = 1 : −0.2 : −0.5 : 0.2 with J ≃ 252 K. The 1/3-plateau phase pertains to polarized magnetic trimers formed by strong J bonds. An effective J→∞ model shows a tendency towards condensation of magnon bound states preceding the plateau phase [2].
[1] H. Ishikawa et al., PRL 114, 227202 (2015).
[2] O. Janson et al., arXiv:1509.07333.