High Frequency Magnetic Property of Dense Fe<SUB>22</SUB>Ni<SUB>78</SUB> Cluster Assembled Films

Abstract

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.