The anisotropy constants K ofγ-Fe_(2)O_(3),Co-γ-Fe_(2)O_(3) and Co ultrafine particles precipitated in Cu-Co alloy have been measured by wing the equations for describing the relaxation of superparamagnetic particle...The anisotropy constants K ofγ-Fe_(2)O_(3),Co-γ-Fe_(2)O_(3) and Co ultrafine particles precipitated in Cu-Co alloy have been measured by wing the equations for describing the relaxation of superparamagnetic particles.It is found that the anisotropy constant K of Co-γ-Fe_(2)O_(3) fine particles is greater than that ofγ-Fe_(2)O_(3) by about 50%;the K value of Co ultrafine particles of a radius equal to 36Åis greater than that of to 48Åby about 100%.This phenomenon has been interpreted as the existence of surface anisotropy of the Co ultrafine particles.展开更多
The microstructure of Nb-coniaining NdDyFeCoB magnets has been vestigated using transmission electron microscope.Very small particles whose diameters are about several to 40A have been found in as-sintered magnets.It ...The microstructure of Nb-coniaining NdDyFeCoB magnets has been vestigated using transmission electron microscope.Very small particles whose diameters are about several to 40A have been found in as-sintered magnets.It may be formed by self-tempering.Dislocations and stacking faults have been found inside grains.It seems that the increase of coercive field in Nb-containing magnets is closely related with defects and precipitations.展开更多
The migration process of Co ions in the cobalt-ferrite epitaxial layer on γ-Fe_(2)O_(3) powder has been studied by magnetic thermal annealing method.The activation energy E and coefficient A of Co ions have been meas...The migration process of Co ions in the cobalt-ferrite epitaxial layer on γ-Fe_(2)O_(3) powder has been studied by magnetic thermal annealing method.The activation energy E and coefficient A of Co ions have been measured.An abnormal increase of coercivity of sample annealed in a transverse magnetic field was found.On the basis of Mdssbauer and XPS results the reason of this phenomenon is discussed.展开更多
基金Supported by the National Natural Science Foundation of China.
文摘The anisotropy constants K ofγ-Fe_(2)O_(3),Co-γ-Fe_(2)O_(3) and Co ultrafine particles precipitated in Cu-Co alloy have been measured by wing the equations for describing the relaxation of superparamagnetic particles.It is found that the anisotropy constant K of Co-γ-Fe_(2)O_(3) fine particles is greater than that ofγ-Fe_(2)O_(3) by about 50%;the K value of Co ultrafine particles of a radius equal to 36Åis greater than that of to 48Åby about 100%.This phenomenon has been interpreted as the existence of surface anisotropy of the Co ultrafine particles.
文摘The microstructure of Nb-coniaining NdDyFeCoB magnets has been vestigated using transmission electron microscope.Very small particles whose diameters are about several to 40A have been found in as-sintered magnets.It may be formed by self-tempering.Dislocations and stacking faults have been found inside grains.It seems that the increase of coercive field in Nb-containing magnets is closely related with defects and precipitations.
基金supported by National Science Foundation of China.
文摘The migration process of Co ions in the cobalt-ferrite epitaxial layer on γ-Fe_(2)O_(3) powder has been studied by magnetic thermal annealing method.The activation energy E and coefficient A of Co ions have been measured.An abnormal increase of coercivity of sample annealed in a transverse magnetic field was found.On the basis of Mdssbauer and XPS results the reason of this phenomenon is discussed.
