Magnetic anisotropy and magnetization dynamics of Fe nanoparticles embedded in Cr and Ag matrices

Abstract

Static and dynamical magnetic properties of Fe nanoparticles (NPs) embedded in non-magnetic (Ag) and antiferromagnetic (Cr) matrices with a volume filling fraction (VFF) of 10% have been investigated. In both Fe@Ag and Fe@Cr nanocomposites, the Fe NPs have a narrow size distribution, with a mean particle diameter around 2 nm. In both samples, the saturation magnetization reaches that of Fe bulk bcc, suggesting the absence of alloying with the matrices. The coercivity at 5 K is much larger in Fe@Cr than in Fe@Ag as a result of the strong interaction between the Fe NPs and the Cr matrix. Temperature-dependent magnetization and ac-susceptibility measurements point out further evidence of the enhanced interparticle interaction in the Fe@Cr system. While the behaviour of Fe@Ag indicates the presence of weakly interacting magnetic monodomain particles with a wide distribution of blocking temperatures, Fe@Cr behaves like a superspin glass produced by the magnetic interactions between NPs.

Keywords:

• magnetic nanoparticles
• nanocomposites
• nanomagnetism
• exchange bias

Acknowledgements

Financial support from the Swedish Research Council (VR) and the Göran Gustafsson Foundation is acknowledged. D. Peddis gratefully acknowledges the COST action MP1308 ‘Towards Oxide based electronics’ for the support of its research activity at the Uppsala University (STSM program).

Disclosure statement

No potential conflict of interest was reported by the authors.