Nanoobjects microscopy

Influence of an external electric field on micromagnetic structural elements in thin ferrite garnet films
Koronovskyy V.E.
Taras Shevchenko Kiev National University, 4-g, Prospekt Glushkova Street, 03127 Kiev, Ukraine
E-mail: koron@univ.kiev.ua

Magnetoelectric (ME) properties of Bloch lines (sub-structural nano-formations) as magnetic topological defects of domain walls in thin films of ferrite garnets have been investigated by us. Earlier we already reported on the results of ME researches of yttrium-iron-garnet films properties using the optical polarimetry method [1,2]. But, disadvantage of the described technique is that the structure of the domain walls separating domains is practically invisible when observed in transmitted polarized light. Using the method of optical dark field microscopy [3] allow to detect micromagnetic structures, with a characteristic size of tenths and hundredths of a micron. I.e, this method allows us to directly visualize the vertical Bloch lines (VBL).  The VBL's we can be seen as regions of local variation (amplification or attenuation) of brightness in images of domain wall segments [3]. We adapted this method to investigate the micromagnetic structural elements of garnet films in external electric fields. The sample was placed between two thin, optically transparent electrodes and the external electric field was oriented perpendicular to the plane of the film. Thickness of the film was about 7 μm. We detected with the direct observations the ME activity of VBL's in external electric field. Effect visually manifested as a broadening of the regions of their localizations. This broadening can be interpreted as the effect of additional amplification in electric field of the initially existing micro-slope of the domain wall region in the vicinity of the VBL. Visually we observed delocalization of the region of "deformation" of the domain wall region. 

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