Enhanced capability in a gas aggregation source for magnetic nanoparticles

Abstract

We describe the characterization of a high-temperature ͑2000 K͒ thermal gas aggregation source that is ultrahigh vacuum compatible and can cleanly deposit transition metal clusters with partial pressures of contaminants in the 10 −11 mbar range allowing codeposition with highly reactive matrices. In particular, we investigate the effect of varying ͑i͒ the bath gas pressure and composition on the size distribution and flux of clusters produced and ͑ii͒ the position of the crucible within the source. The mass spectra of Fe clusters produced, recorded using a quadrupole filter, show that changing the operating conditions and configuration of the source allow a wide range of cluster sizes-3000-320 000 amu ͑ϳ50-6000 atoms for Fe or Co͒ to be produced. We demonstrate the cleanliness of the source by producing uncontaminated Fe clusters in rare-earth matrices.

Matrix and interaction effects on the magnetic properties of Co nanoparticles embedded in gold and vanadium

“…[26][27][28] The gas-phase deposition technique is increasingly used in order to produce the desired nanocomposites, probably due to its versatility in producing high purity nanocomposites with the ability to fine-tune the size distribution and concentration of the nanoparticles. An increasing number of studies on magnetic nanoparticles grown using this technique and embedded in different matrices can be found in the literature including Co [29][30][31][32][33][34][35][36][37][38] Ni, 38,39 Fe 31,37,38,40 and alloy 37,38,[41][42][43] nanoparticles. Magnetic nanoparticles of 3d transition metals (usually Fe, Ni and Co) in contact with non-ferromagnetic matrices present an interfacial anisotropy, 44 whose origin strongly depends on the electronic structure of the nanoparticles, the matrix magnetic behavior and the interparticle interaction energies.…”

Magnetic and structural changes in Cu1−xAlx alloy matrix – Embedded Fe nanoparticle systems

“…A gas aggregation nanoparticle source was used to produce the Fe nanoparticles, while Cu and Al were produced using molecular beam epitaxy (MBE) sources. Detailed information about the nanoparticle source is given elsewhere [29,30]. Briefly, Fe nanoparticles are produced by nanoparticle source direct from gas phase, with a log-normal distribution (diameters) in the 1-5 nm range with a strong peak at around 2 nm.…”

Ferromagnetism of Dy films containing embedded Fe atoms and nanoparticles

“…After thoroughly outgassing the Dy and Fe Knudsen cell sources, films could be grown in a background pressure of 1 Â 10 À 9 mbar . The Fe clusters were produced by a thermal gas aggregation source reported elsewhere [9]. During deposition of the clusters the pressure in the deposition chamber rose to $ 10 À 5 mbar of He but the partial pressure of non-He impurities introduced into the system was in the 10 À 11 mbar regime.…”