Magnetic structure of $La_{8}$$Cu_{7}$$O_{19}$

K. Prokeš (1) , E. Ressouche (2) , A. Mohan (3) , B. Wolter (3) , B. Buchner (3, 4) , C. Hess (3, 4)

1 HZB - Helmholtz-Zentrum Berlin für Materialien und Energie GmbH = Helmholtz Centre Berlin for Materials and Energy = Centre Helmholtz de Berlin pour les matériaux et l'énergie
2 MDN - Magnétisme et Diffusion Neutronique
3 IFW Dresden - Leibniz Institute for Solid State and Materials Research
4 TU Dresden - Technische Universität Dresden = Dresden University of Technology

The magnetic structure of the five-leg ladder compound $La_{8}$$Cu_{7}$$O_{19}$ has been determined using single crystalline neutron diffraction. The material orders antiferromagnetically with the propagation vector q=(12,12,0) below TN=102.5(3)K. Above this temperature the magnetic susceptibility corresponds indeed to that of a five-leg S=1/2 spin ladder, assuming isotropic couplings along the rungs and the legs [J/kB=J′/kB=194(3)K]. Crystallographically, the Cu magnetic moments divide into two subsystems, depending on the environment. Moments situated at centers of octahedra built up by oxygens orient along the b axis and couple to neighboring moments antiferromagnetically, whereas those creating a complicated ribbon structure possess all three Cartesian components. All Cu moments are found to have magnitudes between 0.69 and 1.32μB. Thus, it is seen that the five-leg ladder $La_{8}$$Cu_{7}$$O_{19}$ exhibits long-range antiferromagnetic ordering and possesses a rather complicated magnetic structure which has a noncollinear character.

Domaines: Science des matériaux [cond-mat.mtrl-sci]

K. Prokeš, E. Ressouche, A. Mohan, B. Wolter, B. Buchner, et al.. Magnetic structure of $La_{8}$$Cu_{7}$$O_{19}$. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2017, 95 (2), pp.024405. ⟨10.1103/PhysRevB.95.024405⟩. ⟨hal-01937614⟩