1,720,982 research outputs found
Magnetic interactions in Co-based alloy thin films
No full textThe interactions in ternary and quaternary Co-based alloy thin films for longitudinal recording media, with different thickness, are studied. The analysis is performed through the measurement of the initial magnetization and ordinary hysteresis curves. The interactions result stronger in quaternary than in ternary alloy films and when the film thickness is smaller. These findings are discussed in relationship with the evolution of the magnetic switching, characterized by a tendency towards a more coherent rotation of the magnetization in single-domain grains of thinnest and quaternary films, owing to the complex structure of these films. The impact of this evolution on the thermal stability of the magnetic properties is also discussed
Some aspects of the intrinsic magnetic behavior of metal particles for advanced recording media
No full textThe thermal stability and the magnetic anisotropy of advanced metal particles with high coercivity, useful in high performance recording technology, are investigated and compared with the behavior of previous generation metal particles. The results are discussed in relationship with the findings of the study of the magnetization switching. The role that the better morphological order of the advanced metal particles has in the determination of the basic magnetic behavior is underlined. © 2002 Elsevier Science B.V. All rights reserved
Exchange Anisotropy in Metal-Evaporated Tapes
No full textThe hysteretic properties of commercial Metal Evaporated tapes, consisting of one or three layers of Co-Ni-O, have been analysed at low temperature. When the tapes are cooled from room temperature in the saturation remanence, or in presence of a strong applied field, the hysteresis loops at low temperature are displaced, with dissymmetrical values of the coercive fields. Also the rotational hysteresis has an anomalous behaviour with a monotonic increase with the applied field. These effects are due to the interface action between the ferromagnetic Co and the antiferromagnetic CoO, which, at low temperatures, gives rise to the unidirectional exchange anisotropy. © 1994, American Institute of Physic
Thermal stability of CoCr films for perpendicular recording media
No full textThe thermal stability of the magnetic properties of CoCr thin films for perpendicular recording media is analyzed with measurement of the dependence of the coercivity on the applied field sweep rate, in films with different thickness, Cr content, and presence or absence of a soft FeNi underlayer. The results are discussed on the basis of the evolution of the magnetization reversal mode, owing to the different microscopic structure and magnetic order of the films, which indicates weaker thermal stability of the magnetic properties in films with the smallest thickness, lowest Cr content, and the presence of the FeNi unferlayer
Comparison between different methods for evaluating the anisotropy field distribution in recording systems
No full textThe determination of the anisotropy field distribution P(Ha) is made by the second derivative of the magnetization measured perpendicularly to the easy magnetization direction, in the range from saturation to remanence, for a number of magnetic recording systems. The transverse susceptibility X(H) is measured in the same systems. For the systems where the particles are "perfectly" aligned the peak of P(Ha) is located at the same field of the peak of X(H). In the systems where an appreciable fraction of particles are misaligned the peak of P(Ha) is shifted to lower fields while that of X(H) does not change its position. The coincidence of the two peaks is assumed as a criterion for the validity of the P(Ha) distribution
Thermal relaxation of the magnetization in recording media
No full textThe time dependence of materials for magnetic recording media, both particles and thin films, is studied. The stability, as deduced from the magnetization decay, magnetic viscosity and fluctuation field, is greater in undoped materials with good morphological and structural order. The activation volume is smaller than the physical size in all the particulate materials, and related to the magnetization switching: it shows relative decrease when the reversal does not take place by coherent rotation, as it occurs in doped particles, or when the particles are composed of segregated sub-units. © 1999 Elsevier Science B.V. All rights reserved
The characteristics of the anisotropy field distribution in magnetic recording media
No full textThe anisotropy field distribution is deduced in a number of magnetic recording systems by the second derivative of the branch of the hysteresis curve in the range from saturation to remanence. The distributions so obtained are compared with statistical distribution functions. Generally, the beta or chi-squared distribution functions give the best fits for all samples. The dependence of the anisotropy field distribution on the interparticle interactions and particle misorientation is also analyzed
Thermal relaxation of the magnetic properties in hard disk recording media
No full textThe thermal relaxation of the magnetic properties of thin films for hard disk media is studied. The analysed magnetic layers are constituted of ternary and quaternary Co-based alloy with different thickness. The relaxation is analysed with measurement of magnetic viscosity and of coercive field variability. The magnetization switching of the magnetic films is also discussed with the rotational hysteresis analysis. The different stability in the films is discussed with the evolution of the basic processes of magnetization
A comparison between different methods for evaluating the particle interactions in magnetic recording systems
No full textTwo different methods for the determination of the magnetic interparticle interactions in recording systems are compared.The first one is that based on the evaluation of the deviation DeltaM from the Wohlfarth equation for non interacting particles which requires the measurement of the remanence curves. The other is an easier procedure which consists in the determination of the deviation DeltaM* from an equation based on the initial magnetization curve and the hysteresis loop. For systems of oriented uniaxial anisotropy particles is generally DeltaM = 2 DeltaM*, while for systems of oriented multiaxial particles or of random oriented particles is DeltaM = 4 DeltaM*. The advantage of the second method is its applicability on systems where the initial magnetization curve and the hysteresis loop must be corrected by the demagnetizing field as for CoCr films magnetized perpendicularly to the film plane
Magnetization Of Pressureless Sintered Fe-B Powders
No full textWe report a study about the effects on magnetic properties of pressureless sintering without binder addition performed on iron and boron powder mixture. The obtained self-supported samples appear highly porous or very compact depending on the maximum temperature, T(max), reached during the heating process. They maintain the soft magnetic properties of original Fe-B powder mixture if T(max) does not exceed a critical temperature; afterwards the magnetic properties change very abruptly. A decrease in the magnetization saturation per unit mass, M(s), has been observed to increase the T(max) value. Mossbauer spectroscopy has revealed the presence of Fe2B boride inside the obtained samples whose quantity increases with T(max). Considering the magnetic moment per iron atom in Fe2B as the theoretical one calculated by Ching et al., it has been possible to correlate the T(max) dependence of M(s) with the growing of Fe2B boride. The compacting process seems to be due to the growth of Fe2B boride between Fe/B interfaces
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