As a national pilot institute of the educational reform on practical teaching, an integrative and continuous practical teaching was established and implemented through four measures: promote a practical teaching system that is available for every undergraduate throughout their whole bachelor program; integrate the design of theoretical the practical teaching to closely associate the theoretical course with practical teaching; construct a complete practical teaching system by including experiment teaching, course design, project practice and extracurricular innovative practice; improve the level of practical teaching by appropriately allocating scientific research team, relevant personnel and resource. Based on the exploration and practice of this kind of practical teaching system, the integrative competence and quality of the undergraduates and graduates are both improved.
CoCrPt/Ti/C, CoCrPt/C/Ti and CoCrPt/C/CoCrPt/Ti thin film were prepared to study the effect of thin C layer insertion on the magnetic properties and microstructure of CoCrPt/Ti hybrid recording media. Surface roughness improvement and C atoms' diffusion to Ti underlayer contribute to optimized magnetic properties in CoCrPt/Ti/C films due to C seedlayer insertion. Very thin C intermediate layer gives rise to smaller magnetic grain size and improved perpendicular coercivity in annealed CoCrPt/C/Ti thin film while thicker C intermediate layer hinders the epitaxial growth relationship between Ti underlayer and Co-alloy magnetic layer. 3nm C intermediate layer in CoCrPt/C/CoCrPt/Ti thin film structure helps to obtain smaller grain size and weaker inter-granular exchange coupling interaction in the magnetic layer after annealing process. C atoms' diffusion into Ti underlayer, Co-alloy magnetic layer or grain boundary in magnetic layer plays an important role in the effect of thin C layer insertion on the magnetic property and microstructure of CoCrPt/Ti hybrid recording media.
The authors demonstrate microwave assisted switching process of Ni80Fe20 thin film element with micromagnetics.
Effects of microwave amplitude and frequency on the magnetization reversal were focused. Numerical results showed
that the coercivity of Ni80Fe20 thin film element can be reduced by the modification of the microwave field, and the most
evident reduction of coercivity was found at resonance frequencies. Considerable Fluctuations of switching fields are
found at the natural resonance frequencies and high microwave amplitudes, which can be explained by scattering of
nucleation sites induced by the thermal effect of the microwave filed.
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/cm2; 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.
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.
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/in2. 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 0k. This can be explained with the feeri-magnetical structure of RE-TM alloy. Under the optimized sputtering conditions, when the magnetic layer composition was (Sm0.343Tb0.657)31Co69, the Ms as high as 385emu/cm3 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 Tcomp 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.
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.
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.
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 (Ni0.81Fe0.19)0.66Cr0.34 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 (Ni0.81Fe0.91)0.66Cr0.34 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.
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.
AlNx/DyFeCo films were deposited on glass substrates by magnetron sputtering and reactive rf magnetron sputtering. The influence of AlNx coverlayers on DyFeCo magneto-optical media was studied. The results show that nitrogen surplus in AlNx 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.
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 (TCOMP) decreases, Curie temperature (TC) remains unchanged and the saturation magnetization (Ms) at room temperature increases. Experimental data show good agreement with the calculated results.
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.
In this paper the authors study the effect of temperature in magneto-optical disk recording and the importance of the disk temperature measuring. We design the sensor system for the control and measure of magneto-optical disk temperature. The system is well received by users because of its perfect function in usage software and user interface.
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 Ku, Kerr rotation angle (theta) k and coercivity Hc 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 precision of the laser range finding subsystem has important influences on the performances of the whole measurement system applied to survey the steelmaking converter lining erosion state. In the system, the object of laser beams is some rough lighting surfaces in high temperature. the laser range finding signals to reach the microcomputer system would be submerged in intense disturb environments. Common laser range finding devices could not work normally. This paper presents a method based on the wavelet transform to test solving the problem. The idea of this method includes encoding the measuring signals, decomposing the encoded received signals of components in different frequency scales and time domains by the wavelet transform method, extracting the features of encoded signals according to queer points to confirm the arrival of signals, and accurately calculating out the measured distances. In addition, the method is also helpful to adopt some digital filter algorithms in time. It could make further in improvement on the precision.
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.
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