Magnetic Properties and Microstructures of Co/100-x\Tb/x\ , Fe/100-x\Pt/x\ and (FePt)-(Si/3\N/4\)Thin Films
| Autor: | Chih-Ming Kuo, 郭志明 |
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| Rok vydání: | 1999 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 87 Amorphous Co/100-x\Tb/x\ alloy thin films with the composition of x=7~60 at.% were prepared by dc magnetron sputtering at various powers and argon pressures then annealing in vacuum. Effects of the composition, sputtering power, argon pressure and annealing temperature on the parallel and normal to the film plane magnetic properties have been investigated. The maximum observed perpendicular coercivity was as high as 6000 Oe for the as-deposited Co-Tb amorphous films. The analysis of transmission electron microscopy diffraction patterns and magnetic measurement data indicate that an amorphous film with isotropic magnetic properties can be produced after low temperature annealing. A nearly magnetic isotropic amorphous Co-Tb film with in-plane coercivity of about 2080 Oe was obtained after annealing at 250 ℃ for 60 minutes.. Polycrystalline Fe/100-x\Pt/x\ alloy thin films with the composition of x = 25~67 at.% were prepared by dc magnetron sputtering on natural-oxidized silicon wafer substrates, then postannealed in vacuum at various temperatures and over different periods. The effects of film composition, magnetic layer thickness, annealing temperature, and annealing time on the magnetic properties parallel and normal to the film plane were investigated. Films with high in-plane coercivity could be obtained by annealing the films in the temperature range between 400 ℃ and 650 ℃. The Fe/50\Pt/50\ film annealed at 600 ℃ for 30 minutes in vacuum exhibits a high in-plane coercivity of 10 kOe, as film thickness is about 200 nm. The average grain size is about 85 nm. The film’s Ms value is about 680 emu/cm\3/ and (BH)/max\ value is about 14 MGOe. Comparing the coercivities of the minor loops of furnace-cooled film and ice-water-quenched film, it indicates that origin of the coercivity is domain wall pinning type for ice-water-quenched film and domain nucleation type for furnace-cooled film. (Fe/50\Pt/50\)/100-x\-(Si/3\N/4\)/x\ (x = 0~50 vol.%) nanocomposite thin films were prepared by dc & rf magnetron co-sputtering of FePt and Si/3\N/4\ targets on silicon wafer substrates, then post-annealed in vacuum at various temperatures. The effects of Si/3\N/4\ volume fraction, film thickness, and annealing temperatures on the magnetic properties parallel and normal to the film plane were investigated. The analyses of transmission electron microscopy indicated that the microstructure of the film is an amorphous Si/3\N/4\ matrix with spherical FePt particles dispersed in it, and the particle size of FePt increased with the annealing temperature but decreased with increasing Si/3\N/4\ content. Maximum in-plane squareness and coercivity of the film were about 0.9 and 11 kOe respectively, which occurred at 30-vol.% of Si/3\N/4\ after annealing at 750 ℃ for 30 min. Average particle size of FePt in this film was about 40 nm. Saturation magnetization of the FePt-Si/3\N/4\ film was independent of film thickness but inversely proportional to the Si/3\N/4\ volume fraction. Variation of the films’ coercivity with film thickness was small. The magnetic hardening mechanism and coercivity of the FePt-Si/3\N/4\ composite film were dependent on the Si/3\N/4\ volume fraction. |
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