Controlled magnetic properties of Ni nanoparticles embedded in polyimide films

Satoshi Tomita, Petra E. Jönsson, Kensuke Akamatsu, Hidemi Nawafune, Hajime Takayama

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)


We have studied the magnetic properties of Ni nanoparticles incorporated in polyimide films using dc- and ac-magnetization measurements. Transmission electron microscopy images reveal that both the mean particle diameter (dave) and the volume fraction of particles (ηave) in the composite layer can be controlled independently. In a series of samples with fixed dave, the system with the lowest ηave behaves magnetically as an ensemble of noninteracting superparamagnets. With increasing ηave, typical signatures of the dipole-dipole interparticle interaction, such as an enhanced blocking temperature, are observed. In dense systems, with a particle concentration above the threshold for geometrical percolation, the magnetic response is ferromagnetic due to the exchange interaction between particles in direct contact.

Original languageEnglish
Article number174432
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number17
Publication statusPublished - 2007 Nov 20


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