Prof. Avadh B. Saxena
Los Alamos National Lab, USA
avadh@lanl.gov 
Abstract: Materials exhibiting ferroic phase transitions are ubiquitous in nature. Ferroic materials are those which possess two or more orientation states (domains) that can be switched by an external field and show hysteresis. Typical examples include ferromagnets, ferroelectrics and ferroelastics which occur as a result of a phase transition with the onset of spontaneous magnetization (M), polarization (P) and strain (e), respectively. A material that displays two or more ferroic properties simultaneously is called a multiferroic, e.g. magnetoelectrics (simultaneous P and M). Another novel class of ferroic materials called ferrotoroidics has been recently found. These materials find widespread applications as actuators, transducers, memory devices and shape memory elements in biomedical technology. First I will provide a historical perspective on this technologically important class of materials and then briefly illustrate the relevant concepts. I will discuss their properties, model the transitions at mesoscale and describe their microstructure. I will emphasize the role of long-range, anisotropic forces that arise from either the elastic compatibility constraints or the (polar and magnetic) dipolar interactions in determining the microstructure. Finally, I will discuss the role of colorsymmetry in multiferroic transitions and consider the effect of disorderon ferroic transitions.
Location: 606 Conference Room
Date and time: September 11th, 2011   10:30 A.M—11:30A.M