Auto-oscillation threshold and line narrowing in MgO-based spin-torque oscillators S. Cornelissen, L. Bianchini, G. Hrkac, M. Op de Beeck, L. Lagae, Joo-Von Kim, T. Devolder, P. Crozat, C. Chappert and T. Schrefl EPL, 87 5 (2009) 57001 Published online: 16 September 2009 DOI: 10.1209/0295-5075/87/57001