Complex magnetic internal order in structurally disordered Ni nanoparticles

E. DE BIASI; A. LEÓN-VANEGAS; W.C. NUNES; S.K. SHARMA; P. HADDAD; T. C. R. ROCHA; J. G. SANTOS DUQUE; D. ZANCHET; M. KNOBEL

EUROPEAN PHYSICAL JOURNAL B - CONDENSED MATTER

SPRINGER

Año: 2008 vol. 66 p. 503 - 508

1434-6028

A detailed study of the magnetic properties of colloidal Ni nanoparticles (∼5.2 nm) that do notpresent long range order is presented. Two magnetic contributions were observed at high temperatures (>25 K), a dominating paramagnetic one and a ferromagnetic contribution, detected by ferromagnetic resonance and low field magnetic measurements. Interestingly, the ferromagnetic behavior does not follow a classical superparamagnetic description. The effective anisotropy increases at low temperatures due to interactions among the ferromagnetic clusters, which leads the system to a frustrated state.