Friday, February 17, 2012
Analytical & Experimental Studies on Layered Multiferroic Materials (Macro-Nano)
Greg Carman, Professor, Mechanical and Aerospace Engineering, UCLA
This presentation reviews the research work conducted at UCLA on layered Multiferroic (magnetoelectrics) materials during the last decade ranging from macroscale (millimeters) to nanoscale (30nm). Applications include but are not limited to antennas, memory devices, pulsed power generation and thermal energy harvesting. A multiferroic laminate is defined as a layered structure comprised of ferromagnetic and ferroelectric layers producing energy exchange between magnetization and polarization states. The presentation describes discrepancies observed at the macroscale between analytical predictions and experimental results using a multi-physics shear lag model. Analysis of homogenized multiferroic materials operated at high frequency indicates mechanical response influences the dynamic electro-magnetic wave propagation through these materials. Experimental studies conducted on thin film structures (i.e. 100 nm) using magnetic force microscopy shows that in-plane and out-of plane magnetization changes can be produced with the application of an electric field. These structures are metastable if used with a PMN-PT (011) single crystal operated with pulsed electric fields. Experimental and analytical results are also presented demonstrating that a single magnetic domain structure (~100 x 150 x 10 nm) can be reoriented by 90 degrees with an electric field. These results suggest a new approach for generating magnetic fields in the small scale and may represent a method far superior than that originally discovered by Oersted in 1819 and presently used throughout our society.