Dresden 2009 – wissenschaftliches Programm
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TUT: Tutorien
TUT 1: Tutorial on Multiferroics and Magnetoelectrics
TUT 1.3: Tutorium
Sonntag, 22. März 2009, 17:40–18:30, HSZ 401
Multiphase multiferroics — •Kathrin Dörr — IFW Dresden, Postfach 270116, 01171 Dresden, Germany
This tutorial addresses multiferroic materials and devices comprising two or more ferroic (ferroelectric or magnetic) phases. Single-phase multiferroics are rare and typically work at low temperatures. A combination of appropriate phases can provide multiferroicity and large magnetoelectric coupling also at ambient temperatures, and early applications have been realized.
One crucial issue is how the different ferroic phases must be coupled in order to achieve a large "composite" magnetoelectric effect, i. e. the desirable electric control of magnetic order (or magnetic control of dielectric order). The coupling mechanisms by (i) elastic strain and (ii) charge at the interface between the phases will be discussed. Examples for these cases are a piezoelectric-magnetostrictive layered "sandwich" structure and a field-effect transistor with ferroelectric gate and magnetic channel, respectively. The various designs of the composite materials will be followed through history, ending with self-organized and artificially patterned thin film nanostructures. Finally, the most promising approaches known today will be introduced. These include multiferroic sensors for magnetic ac fields, spin-polarized tunnel junctions with multiferroic barrier and the electrically controlled magnetic exchange bias effect from a BiFeO3 layer.