Eur. Phys. J. B 66, 503-508 (2008)
https://doi.org/10.1140/epjb/e2008-00445-9

Complex magnetic internal order in structurally disordered Ni nanoparticles

¹ Instituto de Física Gleb Wataghin (IFGW), Universidade Estadual de Campinas (UNICAMP), CP, 6165 Campinas, SP, Brazil
² Centro Atoìmico Bariloche (CAB), CP 8400 S.C. de Bariloche, RN, Argentina
³ Laboratório Nacional de Luz Síncrotron (LNLS), 13084-971 Campinas, SP, Brazil

Corresponding author: ^a debiasi@cab.cnea.gov.ar

Received: 6 August 2008
Revised: 22 October 2008
Published online: 9 December 2008

Abstract

A detailed study of the magnetic properties of colloidal Ni nanoparticles (∼5.2 nm) that do not present 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.