Tese
Estudo da anisotropia unidirecional e da histerese rotacional em sistemas com exchange bias
Fecha
2014-08-18Registro en:
RIGUE, Josué Neroti. Study of unidirectional anisotropy and rotational hysteresis in exchange bias systems. 2014. 152 f. Tese (Doutorado em Física) - Universidade Federal de Santa Maria, Santa Maria, 2014.
Autor
Rigue, Josué Neroti
Institución
Resumen
The exchange bias (EB) phenomen occurs due to the coupling between ferromagnetic and
antiferromagnetic material and the main characteristics are the rise of unidirectional anisotropy
and the rotational hysteresis in torque curves.
In this work we have investigated how the unidirectional anisotropy and the rotational hysteresis
are influenced by the change of some characteristics in thin films samples. Among these
are the stacking of layers, the roughness at the interface between the two materials, the difference
in the ferromagnetic layer thickness and the difference between the antiferromagnetic
materials. The study was made by using magnetic torque measurements which were interpreted
using a granular model for the EB. The parameters obtained from the fitting of the model to the
torque curves has also permitted to reproduce data obtained by different magnetic techniques,
especially in samples where the unidirectional anisotropy is greater than the uniaxial anisotropy.
In NiFe=IrMn samples, the unidirectional anisotropy is favored by stacking layers, by increasing
of the interfacial roughness and by the decrease of the ferromagnetic layer thickness, while
the rotational hysteresis is substantially increased as the interfacial roughness increases. For
the NiFe=FeMn sample the highest values of unidirectional anisotropy and rotational hysteresis
were found, as well as a dependence of these parameters with the measuring magnetic field.