The (Sm,Nd)(Tb,Dy)Co thin Film had been prepared with spf-430H r.f.-magnetron sputtering system. The effects of heavy rare earth Tb, Dy substituted by light rare earth Sm, Nd on the magnetic and magneto-optical properties have been investigated. With the increasing of light rare earth Sm, Nd composition, the saturation magnetization Ms, the reflectivity R and the Kerr rotation angle θ<sub>k</sub> are increased, while the coercivity (Hc) is decreased distinctly. This can be explained with the ferri-magnetic structure of RE-TM alloy. Mr/Hc Ratio is increased with the increasing of Sm composition in
SmTbCo and SmDyCo. The influence of composition and sputtering conditions on perpendicular anisotropy films are reported in detail.
CoPtCu nanocomposite films were prepared by magnetron sputtering. The dependences of texture and magnetic properties on film thickness, Cu atomic fraction and annealing conditions are investigated. After annealing at 640°C, (001) orientation was achieved in the Co<sub>41</sub>Pt<sub>49</sub>Cu<sub>10</sub> film, with a coercivity of 8.4 kOe and magnetization of 650 emu/cm<sup>3</sup>. A short-range domain structure is observed indicating weak inter-grains exchange coupling after annealing. The results suggest that this system might be applicable to ultra high-density perpendicular hybrid recording media.
Light rare earth-heavy rare earth-transition metal (LRE-HRE-TM) thin films are a kind of important recording media. A lot of researches have been carried out on the LRE-HRE-TM thin films to improve its properties for data storage application and fruitful results have been achieved. This report gives a glance on the evolution of the research on LRE-HRE-TM recording media. At the same time, combined with the hybrid recording technology, some experimental results obtained on LRE-HRE-TM recording media are discussed, which suggest the promising prospect of the LRE-HRE-TM media in hybrid recording application.
FePt/C and FePt/Ag multilayer films have been prepared by pulsed filtered vacuum arc deposition system and subsequent rapid thermal annealing were performed on SiO<sub>2</sub>/Si (001) substrates. A strong dependence of coercivity and ordering on C concentration was found in FePt/C films. FePt/C nanoparticles started ordering at 350°C, the longitudinal coercivity got to 8.1 kOe and the saturation magnetization got to 802 emu/cm<sup>3</sup> by decreasing C concentration to 21% at 450°. But the coercitity didn't have the same tendency with Ag-doped FePt films. The films with Ag concentration of 22% started ordering at 400°C and the longitudinal coercivity got to 10.6 kOe and the saturation magnetization was 624 emu/cm<sup>3</sup> at 500°C. The obtained results suggest that the films might be applicable to optical-magnetic hybrid recording media.
The minimax optimization method is applied broadly to industrial design, agricultural test, automation, economy and so on. In the field of magnetic recording, we utilize it in determining optimal fabricating conditions of recording thin film media. In the procedure of thin film fabrication, the coercivity, the remenance- hickness product and the squareness ratio of magnetic thin film are considered as multiple-objective functions of these parameters: element composition, atmosphere pressure, substrate temperature, post-annealing temperature and thin film thickness. The optimal fabricating conditions and high performance of CoCrPt thin film are obtained using the minimax optimization based on a series of experiments and data. The coercivity of CoCrPt thin film is up to 3523Oe; the remenance-thickness product is up to 1.75 memu/cm<sup>2</sup>; and the squareness ratio is up to 0.83. The results show that the minimax optimization method can improve the fabricating conditions of recording thin film and is helpful for a short path of achieved high performance of CoCrPt thin film.
Combining the advantages of hard-disk magnetic recording and magneto-optical recording, hybrid recording is regarded as promising candidate for extremely-high density recording technology beyond Tera bits/in<sup>2</sup>. To obtain such high areal density, hybrid recording media are required to have high coercivity and large remanent magnetization at room temperature, the desired temperature dependence of coercivity and magnetization, as well as very short thermal response time. Currently, the researches on the hybrid recording media mainly involve the magnetic hard-disk polycrystalline recording media and the magneto-optical amorphous media. This report presents the latest progresses in the researches on these two kinds of media for hybrid recording.
In order to meet the requirements of high saturation magnetization (Ms) and large coercivity (Hc) at room temperature for hybrid recording, the TbCo/Cr films with perpendicular anisotropy were prepared by an r.f. magnetron sputtering system without applying bias voltage. The influence of sputtering conditions and the effects of Sm substitution on the magnetic and magneto-optical properties of TbCo/Cr films were studied. It was found that although the Hc of TbCo/Cr could be optimized by choosing suitable sputtering parameters, but the partial Tb substituted by Sm will directly affect the magnitude of saturation magnetization Ms and the Kerr rotation angle 0<sub>k</sub>. This can be explained with the feeri-magnetical structure of RE-TM alloy. Under the optimized sputtering conditions, when the magnetic layer composition was (Sm<sub>0.343</sub>Tb<sub>0.657</sub>)<sub>31</sub>Co<sub>69</sub>, the Ms as high as 385emu/cm<sup>3</sup> and the Hc as high as 4.7KOe at room temperature were obtained.
The magnetic and magneto-optic properties of TbCo/Cr thin films were studied. A comparison of the MO properties was made between TbCo thin films with and without Cr underlayer. It was found that Cr underlayer helps to increase the Kerr rotation angle and to enhance the coercivities of TbCo thin films. The effects of the thickness of Cr underlayer and the gas pressure during Cr underlayer preparation on the magnetic and magneto-optic properties of TbCo layers were investigated, as well as the temperature dependence of these properties of TbCo/Cr thin films.
Temperature dependence of the properties of RE-TM thin films is very important for MO recording. In this paper, we studied the temperature dependence of the magnetic and magneto-optical properties of the amorphous LRE-HRE-TM single layer thin films and LRE-HRE-TM/HRE-TM couple-bilayered thin films. For LRE-HRE-TM single layer thin films, the temperature dependence of the magnetization was investigated by using the mean field theory. The experimental and theoretical results matched very well. With the LRE substitution in HRE-TM thin film, the compensation temperature T<sub>comp</sub> decreased and the curie temperature Tc remained unchanged. Kerr rotation angle became larger and the saturation magnetization Ms at room temperature increased. For LRE-HRE-TM/HRE-TM couple-bilayered thin films, comparisons of the temperature dependences of the coercivities and Kerr rotation angles were made between isolated sublayers and couple-bilayered thin film.
In the paper, the relationship among Kerr rotation angle (formula available in paper) thickness and refractive index of transparent dielectric layer on MO films has been deduced theoretically. A scheme based genetic algorithm (GA) for the optimization of dielectric thin film to enhance the magneto-optic effect has been fabricated. GA ameliorates the astringency and the convergent speed. According to the computing program flow chart, the designation of genetic operators was emphatically discussed.
The fatigue characteristic of the amorphous Sm-substituted DyFeCo magneto-optical alloy films fabricated by R.F. magnetron sputtering method were investigated by accelerated pulse training method under the condition of magnetic field modulation plus laser pulse irradiation. The evaluation of fatigue characteristic is determined from the static magneto-optical signal readout level after several writing/erasing repetitions compared with initial level. The experimental dependence of fatigue characteristics is in good agreement with the model based on the JMA equation. Furthermore, the Avrami factor can be derived from the model. Experimental results show that it is very effective in studying the writing/erasing ability of magneto-optical films employed the method of combined the accelerated pulse training with the JMA equation and Sm-substituted HRE-TM alloys can act as a practical medium for MO storage at short wavelength.
An image processing system for magneto-optical recorded domain has been built. Software based on the modern digital image processing techniques has been implemented, including image averaging, background subtraction, boundary detection and so on. With the system, the blurred domain image taken under difficult conditions due to poor contrast and signal-noise ratio can be enhanced and segmented from the background for further quantitative analysis.
Anisotropic magnetoresistance (AMR) effect thin film sensor has a very wide prospect in application. In this paper, we studied the structure, the AMR and the size effect of the Permalloy film with (Ni<SUB>0.81</SUB>Fe<SUB>0.19</SUB>)<SUB>0.66</SUB>Cr<SUB>0.34</SUB> layer as buffer layer. The resistance of NiFeCr is larger than that of Ta and has the same face-cubic structure as NiFe, which could depress the current shunting effectively and be benefit to the formation of the well-textured NiFe layer. The measurements of XRD and AFM showed that, the specimens with (Ni<SUB>0.81</SUB>Fe<SUB>0.91</SUB>)<SUB>0.66</SUB>Cr<SUB>0.34</SUB> and Ta buffer have close surface roughness, while the former had more textured structure. (Delta) R/R decreased and the saturation field increased with the reduction of the width of the AMR stripes etched by ion beam. However, the magnetic field sensitivity could still reach 0.16 percent/Oe when the width reduce to 30micrometers , and could correctly respond to an alternative magnetic field.
The temperature dependence of the amorphous Sm(Tb,Dy)FeCo quaternary alloys films was investigated using the mean-field model in combination with genetic algorithm. It is shown that when the light rare earth element Sm was substituted for the heavy rare earth element Tb or Dy, the compensation temperature (T<SUB>COMP</SUB>) decreases, Curie temperature (T<SUB>C</SUB>) remains unchanged and the saturation magnetization (M<SUB>s</SUB>) at room temperature increases. Experimental data show good agreement with the calculated results.
AlN<SUB>x</SUB>/DyFeCo films were deposited on glass substrates by magnetron sputtering and reactive rf magnetron sputtering. The influence of AlN<SUB>x</SUB> coverlayers on DyFeCo magneto-optical media was studied. The results show that nitrogen surplus in AlN<SUB>x</SUB> leads to changes in the MO behavior of DyFeCo films due to the reaction of Dy with nitrogen. Furthermore, the influence of thickness of AlN films on the coercivity, anisotropy and eigenvalue of Kerr rotation angle of RE-TM films was investigated. The results can be explained based on the internal stress, impurities and the pinning of defects induced by 'peening effects' of high-speed atoms.
A fatigue behavior measurement system for the magneto-optical recording films is designed. In this system, a kind of TRIAC- based L-C series resonance method is proposed and the intensity dividing readout method is adopted to eliminate the fluctuation of the readout laser power.
The genetic algorithm has been adopted to optimize the structure of magneto-optical disk. The results show that this method has advantages over the traditional method such as less constraint, implicit parallelism and global optimization. Additionally, we can get a set of results, not just only one, and the second time optimization can be proceeded based on the first.
The principle of ellipsometry measurement and the foundation of the ellipsoidal equation were detailedly described, and the genetic algorithm was introduced to the calculation for refractivity and thickness of film, which ameliorates the astringency and the convergent speed. Emphatically discussed the designation of genetic operators according to the computing program flow chart.
The thermal stability of amorphous TbFeCo films covered with the protected AlN films prepared by the RF magnetron sputtering system was studied, in order to understand the degradation kinetics in rare-earth transition metal films. The changes of anisotropy K<SUB>u</SUB>, Kerr rotation angle (theta) <SUB>k</SUB> and coercivity H<SUB>c</SUB> with annealing time were measured with the automatic magnetic torque apparatus and the automatic measurement system of MO Kerr effect, respectively. Data clearly show that stress relaxation is responsible for the decrease in the magneto-optical properties after thermal annealing. Furthermore, annealing studies reveal that the thermal stability of magneto-optical properties improves with increasing Ar sputtering pressure-- a trend that is in conflict with the tendency for films sputtered under low Ar pressure to be more oxidation resistant. This trend is attributed to the large stress component that exists at low Ar pressures and its tendency to decrease as a result of annealing.
The analytical expression for the relationship between the eigenvalue and the total value of the Kerr rotation angle is given by adopting the superposion principle of the interference of light in the bilayer-structure coating with transparent dielectric. The mechanism for the enhancement of the Polar Kerr effect can be discussed. Moreover, comparisons with J. Zak' method and discussions of suitability for the expression have enabled the method validation.
SmTbFeCO amorphous films were r.f.-magnetron sputtered from a mosaic target onto glass substrate. The magnetic and magneto-optical properties of SmTbFeCo thin films deposited at different argon pressure, sputtering power and negative substrate bias voltage were studied. It is shown that the deposition conditions strongly affect the reflectivity R, the coercivity Hc and Kerr rotation angle (theta) <SUB>k</SUB>. In order to meet the requirement of magneto-optical recording, it is optimal to choose Ar pressure of 0.47 approximately 0.73 Pa, sputtering power of 300 approximately 350W, and negative substrate bias voltage of -80V approximately -110V.
Ag<SUB>1-x</SUB>Co<SUB>x</SUB> alloy films were prepared by RF magnetron sputtering onto glass substrate. And the samples were annealed at 200 degrees C and 400 degrees C AgCo films with Co contents below 32 at percent are generally superparamagnetic in their as-deposition state. The fraction of Co atoms in the ferromagnetic component increases monotonically with increasing annealing temperature (Ta) and/or at percent Co. The (theta) <SUB>k</SUB> also increase, but for the Co contents above 45 at percent, as the Ta increase, the (theta) <SUB>k</SUB> increase slowly. For Ag<SUB>55</SUB>Co<SUB>45</SUB> (theta) <SUB>k</SUB> equals 0.08 degrees, reflection (R) equals 0.90 and Hc equals 2000 Oe, and for Ag<SUB>50</SUB>Co<SUB>50</SUB> (theta) <SUB>k</SUB> equals 0.10 degrees, R equals 0.85 and Hc equals 2500 Oe are obtained. We found that most film's magnetic hysteresis loops with applied external field H normal to film surface and in film plane are similar. We analyzed these phenomenon according to the film's structure.