Nanoparticles of Ni in ZnO single crystal matrix R.P. Borges, B. Ribeiro, M.M. Cruz, M. Godinho, U. Wahl, R.C. da Silva, A.P. Gonçalves and C. Magén Eur. Phys. J. B, 86 6 (2013) 254 Published online: 10 June 2013 DOI: 10.1140/epjb/e2013-40008-5