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Activation Entropy, Activation Energy, And Magnetic Viscosity, Ralph Skomski, Roger D. Kirby, David J. Sellmyer
Activation Entropy, Activation Energy, And Magnetic Viscosity, Ralph Skomski, Roger D. Kirby, David J. Sellmyer
Roger Kirby Publications
Starting from an exact quantum-statistical description, the influence of the shape of the energy landscape on the magnetic viscosity is investigated. Magnetic phase-space analysis based on Kramers’ escape-rate theory of chemical reaction kinetics theory shows that the activation entropy associated with thermally activated hopping modifies the magnetic viscosity by reducing the attempt-frequency prefactor compared to an earlier prediction by Brown [W. F. Brown, Phys. Rev. 130, 1677 (1963)]. Energetic contributions are analyzed in terms of a model applicable to a range of coherent and noncoherent magnetization processes, and in the long-time limit deviations from the linear logarithmic magnetic-viscosity law are …
Enhancement Of Coercivity In Nanometer-Size Copt Crystallites, Sy_Hwang Liou, S. Huang, Elizabeth S. Klimek, Roger D. Kirby
Enhancement Of Coercivity In Nanometer-Size Copt Crystallites, Sy_Hwang Liou, S. Huang, Elizabeth S. Klimek, Roger D. Kirby
Roger Kirby Publications
In this study, we showed that a magnetic coercivity (Hc) as high as 37 kOe was obtained in a CoPt thin film that contains separated nanometer-size CoPt crystallites. We prepared CoPt thin films with thicknesses of 5 and 175 nm by magnetron sputtering. After annealing in an Ar/H2 atmosphere at temperatures from 650 to 750 °C for 3–12 h, we measured the magnetic properties and found that magnetic Hc relates to annealing temperature, annealing time and film thickness. From atomic force microscopy and magnetic force microscopy studies, the magnetic single domain size of CoPt is …