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Lecture No.118

Title:Phase Transitions in Ferroic and Multiferroic Materials

Speaker:Prof.Avadh Saxena,Los Alamos National Lab, USA

Date/Time: 2013-10-2,9:30-11:00

Venue: Room.313, Material Building A

Inviter: Prof.Jin Xuejun

Biography:

Educational Background/Employment:
  • B.E.(Hons.) Electrical & Electronics Engineering, BITS, Pilani, India (1982)
  • M.Sc.(Hons.) Physics, BITS, Pilani, India (1982)
  • M.A. (Physics), Temple University, Philadelphia (1983)
  • Ph.D. (Physics), Temple University, Philadelphia (1986)
  • Postdoctoral Research:
    • Joint postdoc between Penn State University, University Park and Cornell University (1986-1989)
  • Employment:
    • Consultant/Visiting Scientist, Theoretical Division and CNLS, Los Alamos National Lab (1990-1992)
    • Technical Staff Member, T-11, LANL (1993-present)
    • Adjunct Professor: University of Barcelona, Spain (2002-present)
    • Adjunct Professor: University of Arizona, Tucson (2005-present)
    • Science Advisor: National Institute for Materials Science, Tsukuba, Japan (2007-present)
    • Group Leader, Physics of Condensed Matter and Complex Systems Group (T-4).
Research Interests:
  • Structural Phase Transformations: Mesoscopic (Ginzburg-Landau) modeling of multiferroic, martensitic and actinide materials using nonlinear elasticity. Symmetry, microstructure and response.
  • Nonlinear Excitations in Electronic Materials: Polarons, excitons, breathers, etc. in inorganic and organic semiconductors and their effect on optical, vibrational, transport and other peoperties. Spin phenomena (spintronics) and nanoscale physics.
  • Soft Condensed Matter: Phase separation and role of curvature on the deformation of membranes and vesicles. Thermodynamics of protein nucleation. Viscoelasticity and polymer morphology.
  • Interplay of Nonlinearity, Geometry & Topology: Exactly and quasi-exactly solvable models. Role of topology and curved geometry in materials.
Selected Recent Publications:
1.   A. Saxena et al., Origin of magnetic and magnetoelastic tweed-like precursor modulations in ferroic materials,, Phys.Rev. Lett. 92, 197203 (2004).
2.   F.X. Bronold, A. Saxena and D.L. Smith, Electron spin dynamics in semiconductors,, Solid State Phys. 58, 73 (2004), review article.
3.   R. Ahluwalia, T. Lookman, A. Saxena, and W. Cao, Piezoelectric response of engineered domains in ferroelectrics, Appl. Phys. Lett. 84 3450 (2004).
4.   J. Benoit, E. von Hauff and A. Saxena, Self-dual bending theory for vesicles,Nonlinearity 17, 57 (2004).
5.   P.G. Kevrekidis, A. Khare, and A. Saxena, Solitary wave interactions in dispersive equations using Manton's approach, Phys. Rev.  E 70, 057603 (2004).

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 color symmetry in multiferroic transitions and consider the effect of disorder on ferroic transitions. Much of the excitement in this field stems from the unusual optical, spin and lattice properties of these materials which renders them as truly viable candidates for future metamaterials, e.g. as negative refractive index materials (NIM).

Time:2013-10-2,9:30-11:00
Location:Room.313, Material Building A