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).

Further reading

Nanoscale position sensors: spintronics offer a low-cost alternative to optics (July 2014)
Studies of defects in boron nitride reveal useful properties for devices (Jan 2014)
Competing interactions and stepwise magnetization observed in Fe nanoparticle films (Aug 2013)