Muon-spin rotation study of magnetism in NaxCoO2 single crystals with 0.78 x 0.97C. Bernhard1, 2, Ch. Niedermayer3, A. Drew1, G. Khaliullin2, S. Bayrakci2, J. Strempfer2, R. K. Kremer2, D. P. Chen2, C. T. Lin2 and B. Keimer2
1 University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials (FriMat) Chemin du Musee 3, CH-1700 Fribourg, Switzerland
2 Max-Planck-Institute for Solid State Research - Heisenbergstrasse 1, D-70569 Stuttgart, Germany
3 Paul-Scherrer-Institut - CH-5232 Villigen PSI, Switzerland
received 19 July 2007; accepted in final form 1 September 2007; published October 2007
published online 20 September 2007
By muon spin rotation we investigated the magnetic properties of a series of highly Na-doped NaxCoO2 single crystals with 0.78(1) x 0.97(1). Our data provide evidence for an intrinsically inhomogeneous magnetic state which can be described in terms of hole-doping (Na vacancy)-induced magnetic clusters that percolate at 1-x 0.04 until they yield a bulk magnetic state near x = 0.78. Evidence for a strong (likely geometrical) frustration of the magnetic order is obtained from the anomalous doping dependence of the spin fluctuation rate (above the ordering temperature) which is strongly enhanced at x = 0.78 as compared to x = 0.97.
71.27.+a - Strongly correlated electron systems; heavy fermions.
75.25.+z - Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source X-ray scattering, etc.).
76.75.+i - Muon spin rotation and relaxation.
© Europhysics Letters Association 2007