Aug 28, 2014
The power of torque magnetometry: defect-induced switching in hexaferrite nanostructures
The characterization of defects in nanostructured materials is very important. Defects present in magnetic materials can reduce their performance in applications such as data storage, permanent magnets and magnetic sensors. The detection of these heterogeneities is difficult especially when they are present in a very low concentration within the ferromagnetic system. Now, reporting in Nanotechnology, torque magnetometry is applied to investigate the magnetism of heterogeneities in two-dimensional (2D) hexaferrite structures.
Scientists from Morgan State University, led by Abdellah Lisfi, and their research partners at the University of Indiana (Bloomington) and the University of Maryland (College Park) have developed an innovative experimental method. This is supported with simulations and based on torque magnetometry (see figure 1) to fully investigate the magnetism of heterogeneities in ferromagnetic systems.
The power of this method is reflected in its ability to measure the magnetization symmetry, the switching, the easy axis alignment, the anisotropy magnitude and the concentration of these magnetic defects. The study of interest was conducted on a 2D BaFe12O19 structure with decoupled nano-platelets (see figure 2) grown on oxidized silicon buffered with ZnO.
The presence of reversible and hysteretic kinks at large and low magnetic fields, respectively, in the measured torque curves illustrates the manifestation of magnetic heterogeneities in the low-dimensional ferromagnetic structure. These kinks represent the contribution of magnetic heterogeneities to the global anisotropy of the film. This is in addition to the two-fold symmetry of the major perpendicular anisotropy component. The heterogeneities consist of two types of nanometric crystallites with the same magnitude of anisotropy as the major magnetic phase, but tilted about –74° and 74° from the normal to the film plane.
More information can be found in the journal Nanotechnology (in press).
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About the author
Abdellah Lisfi is the principal investigator of funded research programmes at Morgan State University. His expertise is in the field of magnetism and magnetic materials. The focus of his research includes low-dimensional magnetic systems such as thin films, single crystal magnetic alloys, magneto-electrics and nano-columnar structures.