Seminar Series by Prof. Kannan Krishnan – 2

Department of Materials Engineering
Indian Institute of Science

is pleased to invite you to the seminar on

Magnetism on the mesoscale: Nanotechnology, Lithography, Information Storage and Logic
Prof. Kannan M. Krishnan
Brahm Prakash Visiting Chair
Department of Materials Engineering
Indian Institute of Science, Bangalore
Department of Materials Sciences & Engineering, and Physics
University of Washington
Seattle, USA

at 3:30 p.m.
on 13.1.2016 (Wednesday)
in the Lecture Theatre, Department of Materials Engineering.


There has been a renaissance in magnetism and magnetic materials research on the nanometer length scale, largely driven by size-dependent scaling laws, exchange, proximity and interface effects, advances in fabrication [1,2], and their demonstrated impact in information technologies.

I will begin this lecture with a brief discussion of criteria that define Nanoscience and Nanotechnology and illustrate them with characteristic length scales and size effects that make magnetism ideal, not only for fundamental investigations, but also technological developments on this length scale.

In the second part of this lecture, I will present recent developments in lithographic fabrication of nanoscale elements, emphasizing the facile, low-cost method of nanoimprint lithography. I will then illustrate some fundamental magnetic studies of competing anisotropies in epitaxial grown nanowire arrays [3], manipulating domain wall reversal by shape anisotropy [4] and the properties of three-dimensional “sombrero” shaped s structures [5,6].

Next, I will address the current status of magnetic recording media and discuss the development of next-generation bit-patterned media [7], proposed to sustain the current growth rate of recording densities. I will conclude with a discussion of a novel concept of building Boolean logic gates [8], called magnetic quantum cellular automata, based purely on dipolar coupling of magnetic arrays [9].

1. Wei Zhang and Kannan M. Krishnan, “Epitaxial patterning of thin films: conventional lithographies and beyond”, Jour. Micromech. & Microeng. 24, 093001 (2014)

2. Y. Bao, T. Wen, A.C. Samia, A.P. Khandhar, and Kannan M. Krishnan, “Magnetic Nanoparticles: Materials Engineering and Emerging Applications in Lithography and Biomedicine”, Jour Mater. Sci. , 51, 513-553 (2016)

3. Wei Zhang, Mark E. Bowden and Kannan M. Krishnan, “Nanoimprint-lithography patterned epitaxial Fe nanowire arrays with misaligned magnetocrystalline and shape anisotropies”, Jour. Appl. Phys. 113 17B502 (2013)

4. W. Zhang, D. N Weiss and Kannan M Krishnan, “ Thermal nanoimprint process for high-temperature fabrication of epitaxial exchange-biased metallic nanostructures”, Jour. Micrmech. Microeng. 21, 045204 (2011)

5. Byung Seok Kwon, Wei Zhang and Kannan M. Krishnan, “Sombrero-shaped Fe3O4 nanoelements with tunable out-of-plane and in-plane magnetization components fabricated by nano-imprint lithography”, Jour. Appl. Phys. 115, 17B506 (2014

6. Byung-Seok Kwon, Wei Zhang and Kannan M. Krishnan, “Direct release of Bio-compatible Sombrero-shaped Magnetite Nanoparticles via Nanoimprint Lithography”, Advanced Materials – Interfaces, 2, 1400511 (2015)

7. Zheng Li, Wei Zhang+ and Kannan M. Krishnan, “Large-area patterning of sub-100 nm L10 FePt dots array”, AIP Advances. 5, 087165 (2015)

8. Zheng Li and Kannan M. Krishnan, “Misalignment-free signal propagation in nanomagnet arrays and logic gates with 45°-clocking field”, Jour. Appl. Phys. 115, 17E502 (2014)

9. This work was supported by US-DOE/BES Grant ER45987 and US-NSF Grant DMR-1063489