G.P. Lin

Granular

The granular hcp Co3Pt nano-grains with large perpendicular coercivity (Hcperp) of 3800 Oe and high perpendicular squareness (Sperp) of 0.93 can be achieved by deposited 14 nm thickness of Co3Pt magnetic layer onto the Pt underlayer with thickness of 200 nm and annealing at low temperature of 300degC in a vacuum of 1 mTorr. It is found that the oxygen atoms would diffuse into Co3Pt layer through inter-grains to isolate Co3Pt grains and prevent grain growth that will decrease inter-grains interaction and enhance recording density of the magnetic film. This film revealed its prominent potential to be applied as perpendicular magnetic recording media for ultra high-density recording.

\hbox{Co}_{3}\hbox{Pt}

FePt thin films with different thicknesses (2.5-30 nm) were deposited alternately with Fe and Pt layers on amorphous SiO₂ substrate without any underlayer and then were postannealed at 700°C for 30 min. The dependences of microstructures, degree of ordering, and magnetic properties on FePt film thickness were investigated. The fct-FePt (001) texture films could be obtained by dc magnetron sputtering of (Fe/Pt)_n multilayer on amorphous SiO₂ substrate after annealing at 700°C for 30 min. The increasing degree of L1₀ ordering was probably due to the thicker films providing more L1₀-ordering nucleation sites. The island-like FePt grains formed on the SiO₂ substrates as the film was thinner than 7.5 nm. Both the values of out-of-plane squareness (S_⊥) and coercivity (Hc_⊥) were higher than those of in-plane ones for all film thicknesses. The values of S_⊥ are close to 1 and Hc_⊥ are in the range of 9.0-15 kOe for FePt thin films with a thickness of 5-15 nm after annealing at 700°C for 30 min.

Thin Films With Perpendicular Hard Magnetic Properties for Perpendicular Magnetic Recording Media

The microstructures and magnetic properties of CoPt thin films with thicknesses between 1 and 20 nm deposited on amorphous glass substrate and post-annealing at 600°C for 30 min were investigated. The morphology of CoPt thin film would change from a discontinuous nano-size CoPt islands into a continuous film gradually as the film thickness was increased from 1 to 20 nm. The formation mechanism of the CoPt islands may be due to the surface energy difference between the glass substrate and CoPt alloy. Each CoPt island could be a single domain particle. This discontinuous nano-island CoPt recording film may increase the recording density and enhance the signal to noise ratio while comparing with the continuous film. The as-deposited 5 nm CoPt film revealed the separated islands morphology after annealing at 600°C for 30 min. This nano-size CoPt thin film may be a candidate for ultra-high density magnetic recording media due to its discontinuous islanded nanostructure.

Effect of Film Thickness on Magnetic Properties of FePt Thin Films Deposited on Amorphous

The Co3Pt magnetic layer with thickness of 7~28 nm was deposited onto the Pt underlayer. The as-deposited Co3Pt/Pt double-layered films with or without a 5 nm Pt capped layer were annealed at temperatures between 275 and 375 °C in vacuum of 1 mTorr. The influences of process parameters on perpendicular magnetic properties of Co3Pt thin films were investigated. The Co3Pt film with perpendicular coercivity (Hc⊥) value of 3620 Oe and the perpendicular squareness (S⊥) of 0.7 could be achieved from the Co3Pt(18 nm)/Pt(100 nm) double-layered films by annealing at 300°C. Further added Tb30Co70 film on the Co3Pt/Pt double-layered film could greatly enhance the perpendicular magnetic properties of the film. The Hc⊥ and S⊥ of the Tb30Co70/Co3Pt/Pt film were as high as 6560 Oe and 0.88, respectively, which has significant potential to be applied in perpendicular magnetic recording media.

{\rm SiO}_{2}

When the Ag layer was introduced under the CoPt alloy film which annealed at 700°C, the CoPt/Ag films had large out-of-plane squareness (<i>S</i>_⊥), out-of-plane coercivity (<i>H</i>_c⊥), and saturation magnetization (<i>M</i>_s). They were 0.95, 1432 kA/m, and 390 emu/cm³, respectively. Further, the SiN_x ceramic materials were cosputtered with CoPt on the Ag underlayer at room temperature and then annealed to reduce the grain size of CoPt films. From the field-emission gun high-resolution transmission electron microscope analysis, the particle size of CoPt was about 10 nm as the SiN_x content was 46.2 vol.%. Furthermore, Ag was added into the CoPt-SiN_x films to reduce the transformation temperature of CoPt films from face-centered-cubic to face-centered-tetragonal structure.

Substrate Directly

The (In<inf>15</inf>Sb<inf>85</inf>)<inf>100-x</inf>Zn<inf>x</inf> films (x = 0∼17.4) were deposited on nature oxidized Si wafer and glass substrate at room temperature by magnetron co-sputtering of Sb target and InZn composite target. The optical and thermal properties of the films were examined by a homemade reflectivity thermal analyzer. Microstructures of the films were analyzed by transmission electron microscope (TEM). As x = 0∼17.4, thermal analysis shows that the (In<inf>15</inf>Sb<inf>85</inf>)<inf>100-x</inf>Zn<inf>x</inf> films have two phase transition temperature ranges, 189 °C ∼ 215 °C and 300 °C ∼ 350 °C.

Effect of Thicknesses on the Microstructure and Magnetic Properties of CoPt Thin Films

CoPt/Ag films were prepared by magnetron sputtering on glass substrates and subsequent annealing. The dependence of ordering degree and magnetic properties on Ag film thickness and annealing conditions were investigated. It was found that the Ag underlayer played a dominant role in inducing the (001) texture of the CoPt film after annealing. CoPt films with a thickness about 20 nm and Ag underlayers with a thickness about 70 nm are easy to obtain a well ordering degree and a perpendicular magnetic anisotropy after annealing at 700 °C for 30 min. CoPt/Ag films with a large perpendicular coercivity in the range of 13.5–14.0 kOe and a perpendicular squareness of 0.97 were obtained after annealing at 700 °C for 30 min. Ag underlayer is beneficial to enhance the perpendicular coercivity (Hc⊥) and perpendicular squareness (S⊥) of CoPt film significantly. The ordering degree and perpendicular magnetic properties of the CoPt films which deposited on Ag underlayer are larger than those of the single layer CoPt films.

Co3Pt Nanocomposite Films for Perpendicular Magnetic Recording Media

The FePt films with various thicknesses of 5 to 50 nm are deposited on Si(100) substrate without any underlayer by in-situ annealing at substrate temperature (Ts) of 620°C. A strong (001) texture of L10 FePt film is obtained and presents high perpendicular magnetic anisotropy as the film thickness increases to 30 nm. Further increasing the thickness to above 30 nm, the (111) orientation of L10 FePt is enhanced greatly, indicating that the quality of perpendicular magnetic anisotropy degrades when the FePt film is thicker than 30 nm. The single-layered FePt film with thickness of 30 nm by in-situ depositing at 620°C shows good perpendicular magnetic properties (perpendicular coercivity of 14.0 kOe, saturation magnetization of 473 emu/cm3 and perpendicular squareness of 0.96, respectively), which reveal its significant potential as perpendicular magnetic recording media for high-density recording.

Microstructures and Magnetic Properties of

Fe100-xPtx single-layered films with Pt contents (x) = 32~69 at.% were deposited on natural-oxidized Si(100) substrate by dc magnetron sputtering. Then the films were post-annealed at 700 °C for 3 min by a rapid thermal annealing (RTA) with a high heating ramp rate of 100 °C/sec. Experimental results show that FePt film presented (111) preferred orientation and tended to in-plane magnetic anisotropy as the content of Pt was 32 at.%. When the Pt content was increased to 55 at.%, (001)-textured FePt film was obtained and presented perpendicular magnetic anisotropy. Its out-of-plane coercivity (Hc⊥), saturation magnetization (Ms) and out-of-plane squareness (S⊥) reached to 12.7 kOe, 375 emu/cm3 and 0.8, respectively. These results reveal its significant potential as perpendicular magnetic recording media for high-density recording. Further increasing the Pt content to 69 at.%, the coercivity of FePt film was decreased drastically to below 1 kOe and tended towards in-plane magnetic anisotropy.

{\rm CoPt{-}SiN}_{x} {-}{\rm Ag}

The magnetic properties and microstructure of the CoPt/Ag and SiN_x/CoPt/Ag thin films deposited by dc and rf magnetron sputtering on glass substrates were studied. When the Ag underlayer is introduced to the CoPt film then annealed at 700^degC, the CoPt/Ag film has large out-of-plane squareness (S_perp), out-of-plane coercivity (H_c _perp) , and saturation magnetization(M_s), they are 0.96, 14 kOe, and 420 emu/cm³, respectively. After the SiN_x capping layer is added, it is found that the SiN_x capping layer would inhibit the CoPt (001) texture growth. The M_s value is increased due to the amount of fct CoPt phase is decreased and the inhibition of oxidation by the SiN _x capping layer. The X-ray peak intensity ratio of CoPt (001) and CoPt (111) planes ( I₀₀₁/I₁₁₁ ratio) were decreased after annealing as the SiN_x capping layer is added.