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BB7.04 - Ultra-Low-Energy Straintronics Using Multiferroic Composites 
April 23, 2014   4:45pm - 5:00pm

Multiferroic devices, i.e., a magnetostrictive nanomagnet strain-coupled with a piezoelectric layer, hold profound promise for ultra-low-energy computing in beyond Moore’s law era. Such devices operate according to the principles of converse magnetoelectric effect, i.e., when a tiny voltage of few millivolts (with appropriate choice of materials) is applied across the structure, the magnetization of the magnetostrictive nanomagnet can be switched between its two stable states in sub-nanosecond switching delay while expending a minuscule amount of energy of ~1 attojoule at room-temperature [Roy, K. et al, Nature Highlight, Switching up spin, Nature 476, 375 (2011), Appl. Phys. Lett. 99, 063108 (2011), Phys. Rev. B 83, 224412 (2011), Scientific Reports (Nature Publishing Group) 3, 3038 (2013), J. Appl. Phys. 112, 023914 (2012)]. Such devices have been proposed not only for memory bits, but also for building logic for computing purposes [Roy, K. Appl. Phys. Lett. 103, 173110 (2013), Fashami M.S., Roy, K. et al, Nanotechnology 22, 155201 (2011)]. This study has opened up a new field called straintronics [Roy, K., SPIN 3, 1330003 (2013)] and experimental efforts to demonstrate such electric field induced magnetization switching are considerably emerging too. I would review some recent developments on building nanoelectronics using such multiferroic magnetoelectric materials for our future information processing paradigm.In a recent development, it is shown that in a magnetostrictive nanomagnet, it is possible to achieve the so-called Landauer limit (or the ultimate limit) of energy dissipation [Roy, K., under review]. According to Landauer's principle, postulated by the famous scientist R. Landauer back in 1961, it necessarily dissipates an energy of amount kT ln(2) [~3e-21 joule at T=300 K, k is the Boltzmann constant, and T is temperature], compensating the entropy loss while erasing a bit of information. This is the foundation of the link between information and thermodynamics. Furthermore, I will talk on the scaling limit of multiferroic devices [Roy, K., under review]. Material parameters pose an important impact over the device performance. I will discuss that how the material parameters should be tuned to achieve superior performance while scaling down the device dimensions.On a very recent development, apart from digital computing, I will talk about how multiferroic devices, with appropriate choice of materials, can be utilized for analog computing purposes [Roy, K. and Datta S., in prep.], e.g., voltage amplification, filter. Using tunneling magnetoresistance (TMR) measurement, a continuous output voltage while varying the input voltage can be produced. Finally, I will discuss on how exotic coupling phenomena at the interface between the ferroelectric and ferromagnetic materials can lead to highly-dense yet an ultra-low-energy computing paradigm [Roy, K., under review].

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Keynote Address
Panel Discussion - Different Approaches to Commercializing Materials Research
Business Challenges to Starting a Materials-Based Company
Fred Kavli Distinguished Lectureship in Nanoscience
Application of In-situ X-ray Absorption, Emission and Powder Diffraction Studies in Nanomaterials Research - From the Design of an In-situ Experiment to Data Analysis