Multiferroic

We studied the magnetic properties of nanosized
Ba2Mg2Fe12O22 powder obtained by citrate autocombustion
synthesis. The powder consists of agglomerates
with mean crystallite size of 100 nm. The magnetic
properties of the powder were investigated at 4.2 K and
at room temperature. The values measured of the magnetization
M at a magnetic field of 60 kOe are 22.78 emu/g
and 30.47 emu/g at room temperature and 4.2 K, respectively.
The magnetic phase transition at 183 K is related
to the ferromagnetic-to-spiral spin order and is a precondition
for this material’s exhibiting multiferroic properties.

A study on magnetoelectric phenomena in the barium titanate–barium hexaferrite (BaTiO3–BaFe12O19) composite system, using high resolution techniques including switching spectroscopy piezoresponse force microscopy (SSPFM) and spatially resolved confocal Raman microscopy (CRM), is presented. It is found that both the local piezoelectric coefficient and polarization switching parameters change on the application of an external magnetic field. The latter effect is rationalized by the influence of magnetostric-tive stress on the domain dynamics. Processing of the Raman spectral data using principal component analysis (PCA) and self-modelling curve resolution (SMCR) allowed us to achieve high resolution phase distribution maps along with separation of average and localized spectral components. A significant effect of the magnetic field on the Raman spectra of the BaTiO3 phase has been revealed. The observed changes are comparable with the classical pressure dependent studies on BaTiO3 , confirming the strain mediated character of the magnetoelectric coupling in the studied composites.