Investigation of the size-effect in cobalt-ferrite nanoparticles using photoacoustic spectroscopy P.C. Morais, A.C. Oliveira, A.L. Tronconi, R.L. Santos et E.C.D. Lima J. Phys. IV France, 125 (2005) 505-508 DOI: 10.1051/jp4:2005125117