Fe–Ni alloy cluster-assembled films were obtained by a plasma–gas-condensation-type cluster-deposition method. We studied the magnetic and electrical properties of these assemblies prepared on an electrically grounded substrate [bias voltage (Va) = 0 kV] and on a negatively biased substrate (Va = −20 kV). The packing density and saturation magnetization per volume, Ms, are much larger for the assemblies prepared at Va = −20 kV than those prepared at Va = 0 kV, while the magnetic coercivity, Hc, and electrical resistivity, ρ, are much lower for the assemblies prepared at Va = −20 kV than those prepared at Va = 0 kV. For Ni-rich Fe–Ni alloy cluster-assembled films obtained at Va = −20 kV, the Hc values can become smaller than 160 A/m (the precision limit of our superconducting quantum interference device magnetometer) by adjusting the initial cluster size. The magnetic and electrical properties of Fe–Ni cluster-assembled films are much improved in comparison with those of pure Fe cluster-assembled films.
Both FePt cluster/FeCo film and FeCo cluster/FePt film laminated hybrids have been prepared by combination of a plasma-gascluster-deposition and a helicon-plasma sputter-deposition and studied by X-ray diffraction and magnetization measurements. In FePt cluster/ FeCo film laminated hybrids, M S increases, while H C and BH MAX monotonically decrease with the FeCo film thickness. In FeCo cluster/Fe Pt film laminated hybrids, M S , H C and BH MAX increase with the FeCo cluster layer thickness in comparison with those of simple FePt films. However, the remarkable improvement of their hard magnetic properties cannot be attained in these laminated hybrids owing to both the low packing density of FeCo clusters and the difficulty in the diffusion-control of Fe and Co atoms from FeCo to FePt layers.
Using a plasma-gas-condensation cluster deposition apparatus, Fe 22 Ni 78 clusters are deposited on substrates. When a bias voltage, V A , is applied to a substrate, neutral and charged clusters are formed in a plasma region and hard-landed on the substrate, forming dense Fe 22 Ni 78 cluster assembled films. For specimens prepared without introduction of O 2 gas into a sputtering chamber (the oxygen flow rate, R O2 ¼ 0 mol/s), the magnetic coercivity, H C , decreases, while the saturation magnetization, M S , increases as V A is increased up to 20 kV. The real part of magnetic permeability, 0 is very small for V A ¼ 0 kV and it becomes a few hundreds for V A ¼ 5$20 kV. For the dense Fe 22 Ni 78 clusterassembled films prepared at V A ¼ 20 kV with R O2 6 ¼ 0 mol/s, M S decreases, while the magnetic anisotropy field, H K , and the electrical resistivity, , increase, and the ferromagnetic resonance frequency, f FMR , increases up to a frequency ( f ) range of GHz. There are two magnetically optimized states: (1) 0 ¼ 760 at f ¼ 10 MHz for the specimen prepared at V A ¼ 20 kV with the oxygen flow rate, R O2 ¼ 0 mol/s and the Ar flow rate, R Ar ¼ 4:5 Â 10 À4 mol/s, and (2) 0 ¼ 370 at 10 MHz and f FMR ¼ 1:10 GHz for the one prepared at V A ¼ 20 kV with R O2 ¼ 3:7 Â 10 À8 mol/s and R Ar ¼ 4:5 Â 10 À4 mol/s.
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