Manganese phosphide nano-clusters embedded in a polystyrene matrix

Abstract

A procedure is reported to obtain MnP nanoparticles in powder form or embedded within a polymer (polystyrene) matrix, referred to as Ps:MnP. Ps:MnP nanoaggregates are obtained starting from bulk crystalline MnP or from polycrystalline films grown from the vapor phase on glass substrates. Laser ablation (100 to 200 mW power) is used to produce the nanoparticles within a solvent. This method to produce nanoparticles shows a large dispersion of particle size near the 30 nm range. Ablated nanoparticles are distributed into the polymeric solution and solidified. A study of the nanoparticles structure and magnetic properties of the Ps:MnP nanoaggregates were carried out. The magnetization near room temperature characterizes the ferro- to para-magnetic transition. A critical region extending for more than 4 K, rather than a critical point, has been determined with an apparent or average TC≈284.6±0.5K for the Ps:MnP. A spontaneous magnetization is observed above 300 K, showing that there are nanoaggregates which exhibit ferromagnetism beyond the Curie temperature (∼291 K) of bulk MnP. It is suggested that finite size effects, as well as a wide distribution of sizes, determine the critical behavior in the Ps:MnP magnetically inhomogeneous mesoscopic system.