Interparticle interactions in annealed FePt nanoparticle assemblies

Abstract

Abstract-Thermal treatment of self-assembled FePt nanoparticles reduces the interparticle distances, resulting in dramatic changes in the type and strength of interparticle interactions. Consequently, magnetic properties such as the hysteresis and magnetization reversal mechanisms are strongly affected. It is suggested that controlled annealing of self-assembled nanoparticles may offer a novel approach for producing hard magnetic nanocomposites.

Chemically prepared magnetic nanoparticles

“…205 ) The amount of ordering can be controlled by temperature and annealing time. Since the initial paper on FePt synthesis, 3 there has been an explosion of research on FePt prepared by this method [206][207][208][209][210][211][212][213][214][215][216] or variations on this method 217,218 Fe 2 O 3 have been prepared using this method. 222,223 In this case, the Pt(acac) 2 solution was injected in the hot organic solution, then the temperature was lowered to 70uC and the iron carbonyl was added to the Pt-organic solution.…”

FePt : Al2O3nanocomposite thin films synthesized by magnetic trapping assisted pulsed laser deposition with reduced intergranular exchange coupling

“…For the materials with randomly oriented nanoparticles undergoing coherent rotations without interaction, the remanence ratio is equal to 0.5. The remanence ratio decreases when the nanoparticles exhibit magnetostatic interaction, while it increases when the nanoparticles exhibit exchange-coupled interaction [8]. The intergranular exchange coupling is a key parameter in limiting the media noise in magnetic data storage media, and it should be minimized to increase the signal-to-noise ratio and reduce the media noise.…”

“…In addition, FePt nanoparticles may no longer stay isolated after high temperature annealing. All these annealing effects will increase the intergranular exchange coupling effects in FePt nanoparticles and in turn lower the signal-to-noise ratio (increase media noise) in their potential applications in magnetic data storage [8,9]. An alternative approach is to use the FePt-based nanocomposite thin film, which embeds FePt nanoparticles inside a non-magnetic matrix, such as Al 2 O 3 and MgO.…”

An experimental investigation of dynamic behavior in FePt systems

“…The 6C18 particles are larger than the 4C18 and might therefore generate stronger stray magnetic fields simply due to having larger moments. Interactions between FePt nanoparticles have previously calculated as an energy product (B H ) max [31]. Since the FePt particles are generally monodispersed (the exception was 6C18 which had a 5% contribution of 3 nm particles) and have a given interparticle separation determined through self assembly, a value for the interaction between neighboring particles can be found using the Aharoni relation for the magnetic interaction between spheres [32].…”