Angular Variation Of Coercivity Research Articles

Angular variation of coercivity of interacting fine acicular skeleton particles

For fine, acicular skeleton particles of α-Fe prepared from α-FeOOH, the effect of interparticle interaction on the angular variation ofHc was numerically investigated using a direct expansion scheme of the “chain-of-spheres” fanning model to an interacting chain system forming an orthorhombic type of regular space lattice. The model theory reveals that only magnetostatic lateral interchain interaction can affect the angular variation ofHc. The results have been used to explain the experimentally observed effects of particle morphology and packing fraction on the angular variation ofHc in systems made from fine acicular particles prepared for audio/video magnetic recording media. It is suggested that a local aggregate of the so-called “multiple” type, is unavoidably generated in the system.

Angular variation of coercivity in thin-film media by micromagnetic model

A computer micromagnetic simulation model is employed to study the angular variation of coercivity (out of plane) in thin-film media. Each grain of the film is uniformly magnetized and switches coherently according to the S-W model. The M-H hysteresis loops for applied fields at different angles to the film plane are obtained for various magnetostatic interaction parameters, quantum exchange constants, and easy axis distributions. The angular variation of the coercivity curve exhibits a peak if there is magnetostatic interaction among the grains and qualitatively follows the experimental results well. The peak in the angular variation of coercivity is seen to result from the demagnetizing field. The rotational hysteresis process is also investigated by means of this model. >

Comparison of angular variation of coercivity in various magnetic media

Angular variation of coercivity provides a method for studying magnetization reversal mechanisms and has stimulated theoretical interest, particularly for recording materials. This paper reports our experimental results on the angular variation of coercivity in different magnetic media, and compares these data. These include CoNiCr/Cr-type longitudinal media and Ba-ferrite-type particulate longitudinal media for hard disc applications, and CoNi-type metal evaporated longitudinal media for video-recording. Results from sputtered CoNiCr/Cr media showed a symmetric M-type curve and the peak height decreased with inter-granular coupling. In addition, the peak position also changed systematically with grain decoupling. Results from Ba-ferrite particulate media exhibited curves similar to those for CoNiCr/Cr media having relatively magnetically uncoupled grains. However, oriented Ba-ferrite media prepared by having a magnetic field applied at 30 and 60° with respect to the film-plane, showed a very interesting behavior. In contrast, CoNi films which were prepared by oblique evaporation in the presence of oxygen, showed a canted columnar morphology with an easy axis of magnetization out of the film plane. The resultant angular coercivity features a shifted M-type unsymmetric curve and the shift angle increased with the oxygen content in the film - similar to the oriented Ba-ferrite media. It was noted that at high O2 concentrations the curve deviates significantly from a shifted M-type nature. The microstructures of the aforementioned media will also be discussed.

Comparison of angular coercivity in various magnetic media (abstract)

Angular coercivity provides a method for studying magnetization-reversal mechanisms and has stimulated theoretical interests particularly for recording materials.1 This paper reports our experimental results on the angular variation of coercivity in different magnetic media prepared by various means, and compares these data. These include CoNiCr/Cr-type longitudinal media and Ba-ferrite–type particulate longitudinal media for hard-disk applications, and CoNi-type oblique evaporated longitudinal media for video recording. Results from sputtered CoNiCr/Cr media showed a symmetric M-type curve and the peak height decreased with intergranular coupling.2 In addition, the peak position also changed systematically with grain decoupling. M-type curves were also observed when the underlayer Cr thickness was varied, but the peak location remained unchanged. Results from Ba-ferrite media prepared with different packing densities exhibit similar curves as those for CoNiCr/Cr media. However, oriented Ba-ferrite media prepared by having a magnetic field applied at 30° and 60° with respect to the film plane show a very unique behavior. In contrast, CoNi films which were prepared by oblique evaporation in the presence of oxygen showed a canted columnar morphology with an easy axis of magnetization out of the film plane. The resultant angular coercivity featured a shifted M-type unsymmetric curve, and the shift angle increased with the oxygen content in the film. It is noted that at high O2 concentrations the curve deviates significantly from a shifted M-type nature. The microstructures of the aforementioned media will also be discussed.

Structure and properties of oblique-deposited magnetic thin films

Structural characterizations of angle-of-incidence CoNi films using electron microscopy are reported. Both fixed-angle-of-incidence and continuous-variation-of-incidence films are included. The tangent rule is found to be valid at high oblique angle. The easy axis as measured from the torque curve and angular variation of coercivity in a 170-nm film deposited at 75° is about 15° inclined to the film plane, whereas the columnar axis is about 30°. A weak c-axis texture exists as revealed by the electron diffraction study. The c-axis texture in the continuous-variation-of-incidence films with and without oxygen is not detected by electron diffraction.