Magnetic properties of L1 FePt and FePt:Ag nanocluster films

Abstract

A sputtering gas-aggregation technique has been used to prepare FePt and FePt:Ag nanocluster films. The cluster size was controlled in a range from 3 to 6 nm. FePt cluster films were directly deposited onto Si substrate; FePt:Ag cluster films were fabricated by depositing a FePt cluster layer between a Ag underlayer and overlayer. Nanostructure and magnetic properties of the samples were characterized by x-ray diffraction, transmission electron microscopy, and magnetometry. The high magnetic anisotropy L1 0 fct phase was realized in the films annealed at a temperature of 550°C and above. The orientation of clusters is random. The coercivity increases with an increase of annealing temperature; high in-plane and out-of-plane coercivities, exceeding 10 kOe, were achieved in both FePt and FePt:Ag cluster films after annealing. For FePt:Ag films, the coercivity increases with Ag underlayer thickness, t Ag , and reaches about 17 kOe at room temperature for t Ag ϭ5 nm after annealing at 650°C for 10 min. The high coercivity is closely correlated with the degree of L1 0 ordering and nanostructure of the films.

High density flux of Co nanoparticles produced by a simple gas aggregation apparatus

“…7 In this paper we present the development of a nanoparticle gun ͑NPG͒ based on the magnetron sputtering technique and the gas aggregation method. 5,8,9 In general, this kind of equipment operates in ultrahigh vacuum and is devoted to the production of low fluxes of small nanoparticles with fine size control by mass filtering. Here, our intention was to develop a device as easy to operate as the sputtering system itself.…”

Assembly of high-anisotropy L10 FePt nanocomposite films

“…The most common methods to obtain the c-axis normal to the fi lm plane [(0 0 1) texture] are to use seed or buffer layers, such as MgO. Recently, non-epitaxially grown, highly (0 0 1)-textured L1 0 FePt [9,10] and FePt based fi lms [18] have been obtained by using multilayer deposition plus post annealing. It is found that orientations of FePt grains are affected by many preparation parameters, such as initial as-deposited fi lm structure, composition, annealing time and so on [19,20].…”

“…We have prepared monodispersed FePt clusters with fl uorocarbon (CF x ) shell synthesized by a gas-aggregation technique [8,9]. To form core-shell clusters, CF x gas was applied to the gas-aggregation chamber with various fl ow rates.…”

“…In this paper, we report on recent efforts to fabricate high-anisotropy L1 0 FePt nanocomposite fi lms by three methods: monodispersed core-shell FePt(CF x ) nanocluster-assembled fi lms grown with a gas-aggregation source [8,9], (0 0 1)-oriented FePt L1 0 nanocomposite fi lms synthesized by non-epitaxial growth of multilayers [10,11], chemical synthesis of FePt L1 0 particles in nanoporous alumina and creation of highly anisotropic particle fi lms under external magnetic fi eld [12], and analytical and numerical simulational results on these systems [13].…”

High-energy product exchange-spring FePt/Fe cluster nanocomposite permanent magnets

“…Here, energy products of isotropic magnets reached approximately 20 MGOe. Likewise, cluster formation via gas aggregation [11,12,13] has been used extensively to product nanoscale magnetic particles [14,15,16,17,18,19,20,21]. Rui et al [22] reported, in a preliminary study, on cluster-assembled exchange-spring perma-nent magnets assembled using gas aggregation cluster formation.…”