Thermal fluctuations and longitudinal relaxation of single-domain magnetic particles at elevated temperatures

We present numerical and analytical results for the swiching times of magnetic nanoparticles with uniaxial anisotropy at elevated temperatures, including the vicinity of T_c. The consideration is based in the Landau-Lifshitz-Bloch equation that includes the relaxation of the magnetization magnitude M. The resulting switching times are shorter than those following from the naive Landau-Lifshitz equation due to (i) additional barrier lowering because of the reduction of M at the barrier and (ii) critical divergence of the damping parameters.Comment: 4 PR pages, 1 figur

DIRECTION OF THE MAGNETIZATION OF NICKEL NEAR TUNGSTEN IMPURITIES

On estime la direction du moment magnétique dans Ni polycristallin, près des atomes d'impureté de W, minimisant l'énergie impliquée par la méthode de Ritz. L'angle moyen entre le champ appliqué et le champ au noyau de W est proche de 27° pour un champ appliqué de 1 000 Oe, en concordance avec les conclusions tirées des études expérimentales sur la distribution angulaire des rayons γ émis par W implanté dans Ni.The direction of the magnetic moment in polycrystalline Ni, in the vicinity of W impurity atoms, is estimated by a Ritz-method minimization of the energy involved. The average angle between the applied field and the field at the W nucleus is about 27° at an applied field of 1 000 Oe, in agreement with the conclusions from experimental study of the angular distribution of the γ-rays emitted by W implanted into Ni