Non-Boolean Computation w/Nanomagnets

Congratz to my former PhD advisor Dr. Sanjukta Bhanja who recently published and acknowledged the work we originated in Nature Nanotechnology.

Feature from NSF:
http://www.nsf.gov/news/news_summ.jsp?cntn_id=136758&org=NSF&from=ne

Check out the article here:
http://www.nature.com/nnano/journal/vaop/ncurrent/full/nnano.2015.245.html

Physicists - National Institute for Standard and Technology

I am excited to be joining the Nanoscale Spin Dynamics Group group at NIST. We will be working on understanding the unique spin physics in 2D materials. We will study spin inject and transport into materials, such as graphene, from a spin battery device.

Thanks to the Nanostructure and EM group at BNL

I would like to thank Dr. Yimei Zhu, Dr. Dario Arena, and all my colleagues at Brookhaven National Laboratory for the excellent experience and opportunity to conduct world class research with such amazing people. I look forward to continuing our research collaborations and be in touch soon!

NRC Fellowship Awarded

I have been awarded the prestigious National Research Council Fellowship to pursue fundamental spin properties of 2D and low dimensional materials. Its my privilege to work with Dr. Mark Keller and Dr. Tom Silva in the Quantum Electromagnetic Division at the National Institute of Standards and Technology.

Invited Talk: Fundamental Magnetic Interactions in Patterned Nanostructures: Simulation, Fabrication and High-Resolution Microscopy

Thank you to the organizers of  the 2013 MXLS Workshop "New Opportunities for Magnetic Dynamics and Materials at NSLS-II and MAX-IV” for the invited talk.

Fundamental Magnetic Interactions in Patterned Nanostructures: Simulation, Fabrication and High-Resolution Microscopy

Through the use of complimentary multi-technique experimental approaches, investigations of fundamental magnetic interactions, such as magnetostatic, direct exchange, and indirect exchange, in nanomagnetic structures perturbed by static and high frequency excitation, are presented.

Suggestions of using dipolar coupled single domain patterned nanomagnets for applications such as logic, has demonstrated the potential for low-power room temperature operation. The fundamental evolution of reaching desired states can be described as an energy minimization process, where elements exhibit preferential magnetization axes due to engineered shape anisotropies, and local energy minima are reached utilizing external stimuli and strong magnetostatic interactions. Magnetic Force Microscopy (MFM) was implemented in conjunction with NIST’s micromagnetic framework OOMMF, in order to detail the energies associated with different local ground states of coupled nanomangets. The kink energy and magnetic frustrations in ferromagnetic and anti-ferromagnetic ordered elements in various directional applied fields will also be discussed.

Dipolar interactions produce long range force fields but stronger yet are the quantum mechanical short range exchange interactions of neighboring spins. The competing energies of exchange interactions in domain walls and magnetic flux due to surface charges at boundaries can lead to interesting topological charges in room temperature nanomagnetic systems. In a properly engineered nanodisk, magnetic vortices appear, with two degrees of freedom (chirality and polarity), four degenerate states, and exhibit radial symmetry at equilibrium. Utilizing ferromagnetic resonance, transmission electron microscopy, and x-ray transmission microscopy, details of competing direct exchange, demagnetization, indirect exchange energies in magnetic vortex systems are investigated through the observation of core deformation in static fields. The use of high frequency field excitations applied in-situ in TEM to dual vortex core indirect exchange coupled nanodisk heterostructues and the frequency response probed through the time averaged orbital amplitude are also presented. 

APS March Meeting 2013 Talk

I will be presenting our XTM and TEM microscopy work on interlayer exchange couple magnetic vortices under an applied field.

Element Specific Observation of Interlayer Exchange Coupled Dual Vortex Core Nano  Systems

Abstract:

We report on the magnetic evolution of magnetic vortices in nanoscale and multilayer disk structures. The tri-layer structure consists of Co and Permalloy (Py) layers, coupled across a thin (1nm) Cu spacer that provides strong coupling between the Co and Py layers. Element-resolved full-field XMCD microscopy is combined with ultra-high resolution Lorentz transmission electron microscopy, permitting measurement of both layer-resolved domain patterns and the vortex structure averaged across the tri-layer. We examine the evolution of the vortex structure while the nanostructure is cycled through the M-H hysteresis loop. In particular we will discuss the effects of strong interlayer exchanged coupling on a dual vortex core system, including analysis of the layer-resolved coercivity, and the evolution, deformation, annihilation, and nucleation of the vortices.

The figure above shows the domain wall phase diagram measured via Lorentz TEM under quasi-static applied fields.

NSF Review Panelist

I would like to thank Program Director Dr. Juan Figuero for the opportunity to serve as a technical reviewer panelist at the National Science Foundation.

APS March Meeting 2012 Talk

I will be presenting our work entitled:

 High Frequency Excitation of Nanometer-Scale, Strongly Coupled FM / NM / FM Disks 

Abstract:
There is great interest in the manipulation of magnetic domains in nanostructures from both a fundamental and applications perspective. In particular, the use of resonant frequency excitations permits a power reduction of the driving forces necessary to induce detectable motion in magnetic vortex structures. Here we present an experimental and numerical study of patterned tri-layered disk stacks which are composed of 25nm Permalloy | 1nm Copper | 15nm Permalloy, excited at resonance, ranging from 250-500nm in radii. In-situ Lorentz microscopy was used to acquire time averaged real space images of the vortices' gyrotropic motion and micromagnetic simulations were implemented to further understand the coupled dynamics between the ferromagnetic layers across the thin non-magnetic spacer layer. We discuss the effects of interlayer coupling on the vortex trajectories and resonant frequencies for the individual ferromagnetic layers.

The figure above shows the gyrotropic motion of a vortex core under a high frequency applied magnetic field.

Javier F. Pulecio receives USF's Outstanding Dissertation Award

The Outstanding Thesis/Dissertation (OTD) Awards are intended to recognize those USF graduates who have demonstrated exceptional performance during their graduate careers at USF... links below
http://www.grad.usf.edu/outstanding-thesis.asp
http://www.eng.usf.edu/about/news/07-18-11%20Outstanding%20Dissertation%20Award.pdf

Physics Research Associate - Brookhaven National Labs

I am excited to announce my next professional endeavor at BNL in Dr. Yimei Zhu's Nanostructure and Electron Microscopy group in the department of Condensed Matter Physics and Materials Science. I look forward to making contributions to the group's research and furthering our expertise in magnetism and electron microscopy.

Javier F. Pulecio awarded his Doctorate

Javier F. Pulecio has successfully defended and submitted his dissertation to the University of South Florida and  was awarded his Doctorate of Philosophy in Electrical Engineering in the Fall of 2010.

Javier Pulecio Receives 2010 Hispanic Pathways Award

Tampa, Fla. (September 9, 2010) – Javier Pulecio, a doctoral student in electrical engineering, has been selected as the recipient of the 2010 Hispanic Pathways Award in the student category. His nomination letter describes him as an ‘exemplary student researcher and role model for all students...


http://www2.eng.usf.edu/about/news/09-09-10%20Javier%20Pulecio.pdf