Influences of sputtering gas pressure on microtexture and crystallographic characteristics of Ba-ferrite thin films for high density recording media

Ba-ferrite films with small c-axis dispersion angle Δθ50are suitable for ultrahigh density recording media. The dependences of partial oxygen gas pressure PO2and total discharge gas pressure PTotalon the characteristics of Ba-ferrite films were clarified. It was found that there were three regions, where films were composed of single layer of spinel type ferrite(PO2≤0.002mTorr), mixed layer of spinel and magnetoplumbite type ferrites (0.003 leq P_{O2} leq 0.2mTorr) and single layer of magnetoplumbite type ferrite (PO2>0.3 mTorr). In the range of P02between 0.005 and 0.2 mTorr, spinel-like ferrite layer plays very important role as an underlayer to decrease the Δθ50of the Ba-ferrite layer. Films deposited at relatively low PO2and PTotalexhibit very smooth surface and Δθ50as small as2.5sim3.5deg.     

Influence of temperature on magnetic properties of ion-beam sputter-deposited perpendicular magnetic media

Co-Cr perpendicular magnetic media deposited by ion-beam sputter methods show magnetic properties similar to those obtained by radio frequency (RF) sputtering. Coercivity, ratio of perpendicular to parallel squareness, and X-ray orientation are strikingly improved when the substrate is heated. Independent control of substrate temperature makes ion-beam sputter deposition an attractive candidate for deposition of perpendicular magnetic films.     

High density recording with perpendicular Co-Cr-Nb media and ring heads

Effective double layer structure was investigated by adding Nb to the sputtering source of Co-Cr thin film perpendicular magnetic recording tapes. The output from the tapes was measured with a ring head through to the short wavelength, λ50=0.19 μm (D50=267KFRPI).     

Ag底层对TbFeCo薄膜磁性能的影响

采用射频磁控溅射法在玻璃基片上制备了TbFeCo/Ag非晶垂直磁化膜，研究了Ag底层厚度对TbFeCo薄膜磁性能的影响。原子力显微镜、振动样品磁强计与磁光盘测试仪测量结果表明：薄的银底层具有较高的表面粗糙度可以显著增大TbFeCo薄膜的矫顽力，改善TbFeCo薄膜的磁光温度特性，该薄膜有望用作高密度垂直记录介质与光磁混合记录介质。     

Co-Cr perpendicular magnetic recording tape by vacuum deposition

The relation between the incident angle and the crystallographic orientation of a vacuum deposited Co-Cr film is discussed. Also presented are the magnetic properties and the orientation of both a Ni-Fe underlayer and the Co-Cr film for the double layer medium, and the experimental results about the composition distribution in the co-cr film. The films were deposited on a transporting polymer substrate by continuous vacuum deposition. It is found that the orientation of the Co-Cr film is determined only by the incident angle at the initial point of the film formation, and that deposition efficiency more than 50% can be achieved easily. A double layer medium with Ti film under the Ni-Fe film (Co-Cr/Ni-Fe/Ti medium), which is suitable for perpendicular magnetic recording, is produced by vacuum deposition. Auger depth profile in radial direction of the column of the Co-Cr film shows directly that there is Cr segregation near the columnar grain boundaries.     

Perpendicular magnetization structure of Co-Cr films

In a perpendicular recording system, a Co-Cr film as a medium is capable of storing very high density signals. Lorentz microscopy of 1000 kV TEM was used to observe the structure of recorded magnetizations in Co-Cr films having perpendicular anisotropy. A composite medium of a Co-Cr film with a soft magnetic back layer was shown by Lorentz microscopy to have a horseshoe magnetization structure. The stable antiparallel magnetization of transition in the Co-Cr layer determined the head-on magnetization structure of the soft magnetic back layer, which consists of a new straw-rope domain structure. The perpendicular magnetization structure of the Co-Cr film was found to consist of small domains magnetized through the film thickness which correspond to the columnar microstructure of the film. Since the intrinsic hysteresis loop of a Co-Cr film was shown to essentially have an ideal rectangular shape, it can be concluded that the Co-Cr layer of a composite film can be recorded by an ideal magnetizing process with negligible demagnetizing field at the transition.     

溅射工艺条件对TbFeCo/Pt薄膜磁性能的影响

采用射频磁控溅射法在玻璃基片上成功制得了TbFeCo/Pt非晶垂直磁化膜,系统研究了溅射工艺参数对TbFeCo薄膜磁性能的影响.振动样品磁强计测量结果表明:Tb含量在补偿成分点附近,采用较低的溅射氩气压与Pt底层,有利于提高TbFeCo薄膜的磁性能;当Tb含量为0.24,溅射功率为300W,溅射气压为0.53Pa,薄膜厚度为140nm时,TbFeCo/Pt薄膜矫顽力达到476kA/m,饱和磁化强度为151kA/m,剩磁矩形比超过0.8,该薄膜有望用作高密度光磁混合记录介质.     

Perpendicular magnetic recording with a composite anisotropy film

For a recently proposed perpendicular recording system, a composite anisotropy medium has been developed to improve the recording sensitivity of the perpendicular recording head. The medium is composed of a Fe-Ni soft magnetic film and a Co-Cr perpendicular anisotropy film, which are successively deposited on a base by an r. f. sputtering. By using the new double layer medium, an extremely high recording sensitivity could be obtained, compared with the single layer Co-Cr medium. The recording current needed to saturate the double layer film decreased to one-tenth of that for the single layer Co-Cr film. Although the Fe-Ni layer was soft magnetic material, neither deterioration of the frequency response nor peak shift was observed for the double layer film. The reproduction with a perpendicular head was also investigated, and a high output voltage and a high signal-to-noise ratio were obtained.     

The effect of initial growth layer on magnetic properties of Co-Crfilms

The effect of a Ti underlayer, which increases the perpendicular coercive force of Co-Cr films, was investigated. To clarify the cause of this phenomenon, the film-thickness dependence of the magnetic properties was examined. It was found that the coercive force of a Co-Cr film deposited directly on a polymide substrate decreases drastically when it becomes thinner than 50 nm, whereas in the case of Co-Cr film on a Ti underlayer, a high coercive force is maintained even when the film becomes as thin as 20 nm. The film with the underlayer has a distinct uniform columnar structure, whereas the film without it has a 50-nm-thick initial growth layer with no clear structure. Measurements of the temperature dependence of magnetic properties and observations of segregated microstructures indicate that the improvement of magnetic properties by the insertion of the Ti underlayer is mainly due to the improvement of shape anisotropy resulting from the formation of a distinctly segregated microstructure     

The domain structure and magnetic properties of Co-Cr, Mo films

The magnetic properties of Co-Cr and Co-Mo films prepared by d.c. triode sputtering are discussed. The films are found to have perpendicular magnetisation in certain composition ranges. The magnetic domain structure of the films as observed by Lorentz electron microscopy is interpreted in terms of the deposition parameters and the properties of the films. In particular the microstructure of the films is seen to have an overwhelming influence on the domain structure.     

High-energy Co-Cr thin films sputtered on glass disks forperpendicular recording

The authors have developed high-energy Co-Cr thin-film perpendicular recording media for rigid disks. They obtained high perpendicular coercivity (Hc⊥) exceeding 2000 Oe with Co-Cr films sputtered on glass disks. They examined recording characteristics obtained with double-layered media and single-pole heads. Readout voltages were proportional to Hc⊥ up to 2000 Oe and not dependent on saturation magnetization. The authors explain the experimental results using the hysteresis curve of the Co-Cr film and the permeance factor determined by the magnetic reluctance of the head and medium. Using a magnetic circuit model, they clarify the effect of the difference in the operating point on the hysteresis curves of rigid- and flexible-disk systems     

Properties, preparation, advances and limitations of materials andmedia for perpendicular recording

The trends in perpendicular magnetic recording research are discussed, with emphasis on clarifying the trend of research on recording media, their materials, and head materials. Among numerous proposed perpendicular recording media materials, barium ferrite powder and evaporated Co-Cr films seem to lead in practical applications, since their mass production seems to be very successful. There still exist crucial points in their development. However, improvements are continuously taking place. Other candidate perpendicular recording media for a device which has a ring head are also discussed. It is concluded that, for future high-density magnetic recording, utilizing fully the perpendicular component of media magnetization will furnish the key to success     

Effect of annealing in external magnetic field on the microstructure and magnetic properties of FePt films

We have studied the influence of annealing in an external magnetic field on the microstructure and magnetic properties of a multilayer Si/Fe(2 nm)/Fe₅₀Pt₅₀(20 nm)/Pt(2 nm) structure synthesized by means of sequential RF magnetron sputtering of the components. The magnetic field was oriented perpendicular to layers of the structure. It is established that annealing in the external magnetic field leads to the formation of predominant (001) texture in the multilayer structure with L1₀-FePt phase. Thus, a method of obtaining multilayer structures based on FePt films required for the perpendicular magnetic recording has been developed.     

Structure and magnetic properties of Fe films with pyramid-like nanostructures deposited by oblique target direct current magnetron sputtering

Fe thin films were deposited by oblique target direct current magnetron sputtering on Si (100) and (111) substrates. The structure, surface morphology and magnetic properties of the thin films were characterized using X-ray diffraction, field emission scanning electron microscopy, and superconducting quantum interference device magnetometer, respectively. The results reveal that the structure of the as-deposited Fe thin films is body-centered cubic with the preferential [110] crystalline orientation. A pyramid-like nanostructure with sharp tip was formed on the surfaces of Fe thin films under appropriate sputtering power. Formation of the pyramid-like nanostructure is mainly owed to the enhancement of atomic mobility and the bombardment effect with increasing of sputtering power. Meanwhile, the crystalline orientation of Si substrate and the intrinsic stress in the films are expected to have little contribution to the formation of the pyramid-like nanostructure. The magnetic anisotropy was found in the as-deposited Fe thin films, and varies with the thickness of the Fe thin films. As the film thickness increases from 604 to 1,786 nm, the magnetic anisotropy field and the uniaxial anisotropy constant increase from 3.8 to 5.6 kOe, and from 0.4 × 10⁶ to 1.1 × 10⁶ erg/cm³, respectively, which indicates that besides magnetocrystalline anisotropy, stress induced anisotropy and shape anisotropy also exist in the as-deposited Fe thin films.     

Extremely high bit density recording with single-pole perpendicular head

Since perpendicular magnetic recording is free from recording demagnetization, high-density recording up to the intrinsic limit of a recording medium is possible. This prediction was verified experimentally in a flexible disk system using a single-pole head and a Co-Cr/Ni-Fe double-layer medium. We could record and reproduce signals up to 680KFRPI. The recording bit length at the highest density was of the order of the Co-Cr columnar diameter.     

Mössbauer spectroscopy study of amorphous TbFeCo films for perpendicular magnetic data recording

Amorphous films of the Tb _x Fe_{(100 − x − y)}Co _y system with a thickness of ∼200 nm were deposited by RF magnetron sputtering at various pressures of argon (P _Ar) in the working chamber. It is established that the easy axis in Tb₂₉Fe₆₁Co₁₀ films is oriented at an angle of 15° ± 4° relative to the normal to the film surface, whereas in Tb₂₆Fe₆₅Co₉ films this axis is parallel to the normal. The properties of the Tb₂₆Fe₆₅Co₉ films deposited at P _Ar = 5 mTorr meet the requirements to media for the perpendicular magnetic data recording.     

Preparation of Epitaxial MgO Films Deposited by RF Magnetic Sputtering on the IBAD-MgO Substrate

We deposited epi-MgO films on the textured ion beam assisted deposition (IBAD)-MgO substrates by RF magnetic sputtering at different substrate temperatures (600–850 °C), RF powers (110–224 W) and oxygen partial pressures (19.5–58.6 mTorr). The microstructure and surface morphology of epi-MgO films were characterized by X-ray diffraction (XRD) and atom force microscope (AFM). It was found that epi-MgO films with c-axis orientation could be easily fabricated for broad parameter ranges. But the in-plane full width half maximum (FWHM) of the epi-MgO film was dependent on the parameters, and the epi-MgO film with the smallest FWHM value of 5.22° was obtained at the optimum parameters. What’s more, the GdBa₂Cu₃O₇ films deposited on the epi-MgO/IBAD-MgO substrate by RF magnetic sputtering showed c-axis orientation.     

Influence of RF power on structural,morphology, electrical,composition and optical properties of Al-doped ZnO films deposited by RF magnetron sputtering

In this study, influence of RF power on the structural, morphology, electrical, composition and optical properties of Al-doped ZnO (ZnO:Al) films deposited by RF magnetron sputtering have been investigated. Films were systematically and carefully investigated by using variety of characterization techniques such as low angle X-ray diffraction, UV–visible spectroscopy, Raman spectroscopy, Hall measurement, X-ray photoelectron spectroscopy, field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy etc. Low angle X-ray diffraction analysis showed that the films are polycrystalline with hexagonal wurtzite structure and which was further confirmed by Raman spectroscopy analysis. Its preferred orientation shifts from (102) to (002) with increase in RF power. The average grain size was found in the range of 15–21 nm over the entire range of RF power studied. The FE-SEM analysis showed that grain size and surface roughness of ZnO:Al films increase in with increase in RF power. The UV–visible spectroscopy analysis revealed that all films exhibit transmittance >85 % in the visible region. The optical band gap increases from 3.37 to 3.85 eV when RF power increased from 75 to 225 W. Hall measurements showed that the minimum resistivity has been achieved for the film deposited at 200 W. The improvement in the electrical properties may attribute to increase in the carrier concentration and Hall mobility. Based on the experimental results, the RF power of 200 W appears to be an optimum sputtering power for the growth of ZnO:Al films. At this optimum sputtering power ZnO:Al films having minimum resistivity (8.61 × 10^?4 Ω-cm), highly optically transparent (~87 %) were obtained at low substrate temperature (60 °C) at moderately high deposition rate (22.5 nm/min). These films can be suitable for the application in the flexible electronic devices such as TCO layer on LEDs, solar cells, TFT-LCDs and touch panels.     

Reduction of Coercivity of Fe-N Soft Magnetic Film by Heat Treatment

200 nm thick Fe-N magnetic thin films were deposited on glass substrates by RF sputtering. The as-deposited films havehigh saturation magnetization but their coercivity is also higher than what is needed Therefore it is very important to reducecoercivity.The samples were vacuum annealed at 250℃ under 12000 A/m magnetic field. When the N content was in therange of 5～7 at. pct, the thin films consisted of α'+α" after heat treatment and had excellent soft magnetic properties of4πM_s=2.4 T, H_C<80 A/m. However, the thickness of a recording head was 2 μm, and H_c increased as thickness increased.In order to reduce the H_c, the sputtering power was raised from 200 W to 1000 W to reduce the grain size. 2 μm Fe-N thin     

Structural morphology and magnetism of electroless-plated NiP films on a surface-modified Si substrate

NiP thin films were deposited on an H₃PO₄-etched Si substrate by means of electroless-plating. By varying the plating time, we were able to deposit NiP films with various thicknesses. Thickness effects upon the structural morphology and magnetic properties of the NiP films were investigated, and they can be comprehended with a model of the deposition mechanism. The results demonstrate that the etched Si surface contained groove-like microstructure which shaped the columnar structure inside the NiP films and favored the film deposition; this was hard to achieve with a smooth-surfaced Si substrate. The well-developed columnar structure resulted in a perpendicular anisotropy due to its vertical nature, which can become superior to the film's longitudinal anisotropy if the applied field is sufficient.