CRYSTALLOGRAPHY OF THE FERROMAGNETOELECTRIC SWITCHING AND TWINNING.

Basic symmetry properties of ferromagnetoelectric domains are examined by a single group theoretical procedure. Possible types of ferromagnetoelectric switching and the crystallographic coupling between ferroelectric and ferromagnetic switching are discussed. It is shown that the orientation and the charge of coherent stress-free domain walls can be determined by symmetry considerations. Domain structure and switching properties of the orthorhombic ferromagnetoelectric boracites are analyzed as an illustrative example.