Early stages of direct L10 FePt nanocluster formation: The effects of plasma characteristics

Abstract

Patterson, M. M.; Cochran, A.; Ferina, J.; Rui, X.; Zimmerman, T. A.; Sun, Zhiguang; Kramer, Matthew J.; Sellmyer, David J.; and Shield, Jeffrey E., "Early stages of direct L1 0 FePt nanocluster formation: The effects of plasma characteristics" (2010 The formation of FePt nanoclusters via gas condensation has attracted a great deal of attention. The clusters normally form with the magnetically soft A1 structure rather than the desired L1 0 structure with high magnetocrystalline anisotropy. This work has examined the effects of plasma characteristics on the early stages of order in the formation L1 0 FePt nanoclusters via inert gas condensation. The plasma characteristics have been modified to control ion density in the nanocluster condensation region. Increased ion density results in more cluster-ion collisions. The energy imparted to the clusters as a result of these collisions allows atomic rearrangements to form the ordered structure. The results indicate that controlled ion density directly impacts the early stages of FePt nanocluster ordering, according to high-resolution electron microscopy structure observations and coercivity measurements.

Magnetism of directly ordered Sm-Co clusters

“…160 W is expected to result in highly energetic and dense ions in the gas aggregation region, which leads to an increase in clusterion collision probability and subsequently provides sufficient energy for crystallization. 16 The magnetic properties of Sm-Co nanoparticles were investigated by measuring the magnetization M as a function of applied magnetic field H at 300 and 10 K. Figure 3 shows room-temperature hysteresis loops for Sm-Co nanoparticles prepared at different P dc . Poorly crystalline SmCo 5 nanoparticles prepared at P dc ¼ 100 W exhibit a very low coercivity (H c ) of 100 Oe and a remanence ratio of M r /M s ¼ 0.23 at 300 K, as noted in Fig.…”

Investigation of the magnetic properties of FeAu nanoclusters in a W matrix: Evidence for exchange-bias phenomenon

“…[18][19][20] The base pressure of the condensation chamber was less than 10 À7 Torr. An Ar/He gas mixture was introduced into the cluster forming chamber, in which Ar was used for the sputtering purpose and He was used to ensure temperature uniformity inside the nucleation chamber.…”

Laser-assisted atom probe tomography investigation of magnetic FePt nanoclusters: First experiments

“…FePt clusters were created by inert gas condensation [7] from a composite sputtering target consisting of Pt pieces in an Fe target, biased at 360 V (150 W), drawing 330 mA of plasma current (Fig. 1).…”

“…Recent work has examined the effects of plasma characteristics on the early stages of order in the formation L1 0 FePt nanoclusters via inert gas condensation [7]. The results indicate that controlled ion density directly impacts the early stages of FePt nanocluster ordering.…”