Chemistry Graduate Seminar by Dr. Ashok Kumar

Date: Mon, September 19, 4:00pm-5:30pm

Where : FB 341

Description :

"Multiferroics Memory: A Disruptive Technology or Future Technology?"

Multiferroic term is coined for a materials possess at least two or more ferroics order in same or composite phase, if both the ferroic orders are coupled together it is known magnetoelectric (ME) multiferroics. Two device aims for ME multiferroics are switching of polarization by magnetic fields and of magnetization by electric fields. The first effect is useful for magnetic field sensors and for memory elements if, for example, polarization switching is via a very small magnetic field from a coil underneath an integrated circuit. The latter effect is suitable for nondestructive low-power, high-density magnetically read and electrically written memory elements. If the system possesses additional features, such as propagating magnon (spin wave) exctations at room temperature, additional functional applications may be possible. Magnon-based logic systems have been initiated by various scientists, and prototype devices show potential for future complementary metal oxide semiconductor (CMOS) technology. The major drawback of magnon logic devices is the slow group velocity (two orders of magnitude less that speed of light) and high attenuation (six orders of magnitude higher than for photons in optical fibers), but magnetic domain velocities can be supersonic, unlike ferroelectric or ferroelastic domain walls, which gives magnetic random access memory an advantage over Ferroelectric random access memory. For practical applications it is important that material properties should be observable in (CMOS-compatible) thin-film form and at ambient temperatures. Discovery of high polarization, magnetization, piezoelectric, spin waves (magnon) magneto-electric, photovoltaic, exchange bias coupling, etc. make BiFeO3 one of the widely investigated materials in this decade. In this seminar, I will talk on the basic features of ME multiferroics and only known room temperature single phase BiFeO3 in thin films.