Observation of the spontaneous vortex phase in the weakly ferromagnetic superconductor : A penetration depth studyE. E. M. Chia, M. B. Salamon, T. Park, H.-J. Kim, S.-I. Lee and H. TakeyaEurophys. Lett., 73 5 (2006) 772-778DOI: https://doi.org/10.1209/epl/i2005-10465-7