Order–disorder transformation in FePt nanoparticles studied by ferromagnetic resonance

Thickness and temperature dependence of the dynamic magnetic behavior in disordered FePt films

“…Note that even the annealing at relatively low temperatures (T ann ¼ 200 C) produces irreversible changes in the magnetic properties of the films, although the total intensity does not change significantly in this case. When treated at higher temperatures the films start to transform partially to the high anisotropy L1 0 phase which in general could not be observed in a standard FMR experiment due to small exchange length caused by the extremely large value of H U [21,8,9]. The estimated exchange length for the L1 0 phase is around 1 nm (considering an exchange stiffness constant A ¼ 10 À6 erg=cm [1] and a magnetocrystalline anisotropy of 7 Â 10 7 emu=cm 3 [11]) while that of the A1 phase is close to 10 nm which is similar to the average grain size that we have observed by TEM in as-made samples.…”

“…These properties make the alloy a potential candidate for ultrahigh density magnetic recording media, and considerable effort has been devoted to study FePt in the form of thin films and nanoparticles [1,[6][7][8][9][10]. The singular magnetic properties are observed when the intermetallic alloy is close to the equiatomic composition and the Fe and Pt atoms are ordered in the crystal cell.…”

Ferromagnetic resonance

“…The technique of FMR can be applied to nano-systems (Poole, 2003;Parvatheeswara, 2006;Mills, 2006;Schmool, 2007;Vargas, 2007;Seemann, 2009;Wang, 2011;Patel, 2012;De Biasi, 2013). The FMR measurement on a square array of permalloy nanodots have been comparion a numerical simulation based on the eigenvalues of the linearized Landau-Lifshitz equation (Rivkin, 2007).…”

“…The ferromagnetic resonance of magnetic fluids were theoretically investigated on thermal and particles size distribution effects (Marin, 2006). The FMR applied to nanoparticles, superparamagnetic particles and catalyst particles (de Biasi, 2006;Vargas, 2007;Duraia, 2009).…”