In-field Mössbauer study of the disordered surface contribution in nickel ferrite nanomagnets - Sousa, E C; Sousa, M H; Rechenberg, Hercilio Rodolfo; Goya, Gerardo Fabían; Tourinho, F A; Perzynski, R; Depeyrot, Jérôme (Journal of Magnetism and Magnetic Materials, 2007)