Helical order and multiferroicity in the S = 1/2 quasi-kagome system KCu3As2O7(OD)3

G. J. Nilsen (1) , Y. Okamoto (2) , H. Ishikawa (2) , Virginie Simonet (3) , Claire Colin (4) , Andres Cano (5) , L. C. Chapon (6) , T. Hansen (6) , H. Mutka (6) , Z. Hiroi (2)

1 ILL - Institut Laue-Langevin
2 Institute for Solid State Physics
3 NEEL - MagSup - Magnétisme et Supraconductivité
4 NEEL - MRS - Matériaux, Rayonnements, Structure
5 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
6 NEEL - Institut Néel

Several Cu$^2$$^+$ hydroxide minerals have been recently identified as candidate realizations of the S=1/2 kagome Heisenberg model. In this context, we have studied the distorted system KCu3As2O7(OD)3 using neutron scattering and bulk measurements. Although the distortion favors magnetic order over a spin liquid ground state, refinement of the magnetic diffraction pattern below TN1=7.05(5) K yields a complex helical structure with k=(0.77,0,0.11). This structure, as well as the spin excitation spectrum, are well described by a classical Heisenberg model with ferromagnetic nearest neighbor couplings. Multiferroicity is observed below TN1, with an unusual crossover between improper and pseudoproper behavior occurring at TN2=5.5 K. The polarization at T=2 K is P = 1.5 μCm−2. The properties of KCu3As2O7(OD)3 highlight the variety of physics which arise from the interplay of spin and orbital degrees of freedom in Cu2+ kagome systems.

Domaines: Electrons fortement corrélés [cond-mat.str-el]

G. J. Nilsen, Y. Okamoto, H. Ishikawa, Virginie Simonet, Claire Colin, et al.. Helical order and multiferroicity in the S = 1/2 quasi-kagome system KCu3As2O7(OD)3. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2014, 89 (14), pp.140412(R). ⟨10.1103/PhysRevB.89.140412⟩. ⟨hal-00986108⟩