We present a detailed study on the magnetic order in the undoped mother compound LaOFeAs of the recently discovered Fe-based superconductor LaO1−xFxFeAs. In particular, we present local probe measurements of the magnetic properties of LaOFeAs by means of 57Fe M\"ossbauer spectroscopy and muon spin relaxation in zero external field along with magnetization and resistivity studies. These experiments prove a commensurate static magnetic order with a strongly reduced ordered moment of 0.25(5) μB at the iron site below T_N = 138 K, well separated from a structural phase transition at T_N = 156 K. The temperature dependence of the sublattice magnetization is determined and compared to theory. Using a four-band spin density wave model both, the size of the order parameter and the quick saturation below T_N are reproduced.
@article{arxiv.0805.0264,
title = {Commensurate Spin Density Wave in LaOFeAs: A Local Probe Study},
author = {H. -H. Klauss and H. Luetkens and R. Klingeler and C. Hess and F. J. Litterst and M. Kraken and M. M. Korshunov and I. Eremin and S. -L. Drechsler and R. Khasanov and A. Amato and J. Hamann-Borreo and N. Leps and A. Kondrat and G. Behr and J. Werner and B. Buechner},
journal= {arXiv preprint arXiv:0805.0264},
year = {2008}
}