Sunday, July 27, 2014

Summer Investigations in Theoretical/Computational Condensed Matter Physics

This summer has been an exciting time for JMU's Complex Materials Group. Charles (Brock) Crook and Greg Houchins joined Dr. Haraldsen (@nuclearbologna) for some exciting investigations into computational and theoretical physics. Brock has been working on understanding magnetic interactions between impurities in graphene and Boron Nitride, while Greg has been working to determine analytical representations for the inelastic neutron scattering excitation coefficients of symmetric and asymmetric magnetic dimer systems.

Overall, we will be presenting our findings at the JMU Summer Research Symposium (July 29th and 30th) and we are planning to submit these articles for peer-reviewed publication.

Superexchange Interactions of Magnetic Impurities in Graphene

Graphene is a wonderful material that has very interesting electronic properties and has possible technological advantages. To help investigate how magnetic infusion can help this material break into the arena of spintronics, Brock is using Atomistic Toolkit to perform complex density functional calculations on different magnetic impurities in a supercell of graphene with 128 atoms (below). We are investigating changes in the magnetic and electronic structure and interactions with different variations of configuration and ion.

A supercell of graphene with 2 magnetic impurities (above) in the "star destroyer" configuration.
This name came from the obvious resemblance to the Star Wars(R) spaceship (below).
Image via Disney(R)

Understanding the Ground State Excitations in General S1-S2 Dimeric Systems

Understanding the fundamental interactions between magnetic moments is critical for pushing the science of spintronics and magnetic switching devices forward. Therefore, Greg has been working on calculating the inelastic neutron scattering structure factors for various excitations in mixed valence dimeric systems (two interacting spins of S1 and S2). This will allow for better understanding of larger systems since they are built on the foundation of subgeometric magnetic clusters. Through an analysis of these systems, Greg has been able to determine an analytical representation that will help experiments characterize the magnetic systems by looking at the relative intensities between excitations.

Magnetic splitting of a spin-1 and spin 1/2 dimer.

Thursday, July 17, 2014

Infrared power generation: UPDATES

This summer the Undergraduate Students Kyle Britton, Justin Kaczmar and Graham Gearhart joined Harkirat Mann and Brian Lang to do research with Dr. Scarel!  Kyle and Justin are working on the the angular dependence of infrared power generation, while Graham is studying the relationship between the output of the infrared source with time and the voltage produced by the device used to harvest infrared radiation.  In July, Harkirat and Brian went to the Center of Nanophase Materials Sciences at the Oak Ridge National Laboratory (TN) to perform experiments with a laser emitting in the near infrared region.  Recently, a new paper from the group was accepted: H.S. Mann,Y. Schwab, B.N. Lang, J.L. Lancaster, R.J. Parise, and G. Scarel, Effective thermoelectric power generation in an insulated compartment.  World J. Cond. Matter Phys. Vol. 4 (3), (2014).

Here is a figure from the paper: in thermoelectric power generation, the voltage trends in time follow faithfully the trends of temperature difference in the same time interval!  Simple but not trivial: in infrared power generation this symmetry is broken down!

Sunday, June 22, 2014

Induced Ferromagnetism at BiFeO3/YBa2Cu3O7 Interfaces

Dr. Haraldsen (@JMU Physics and Astronomy) and collaborators from Los Alamos National Laboratory (@LANL) and Nanyang Technological University just published a paper in Scientific Reports (@SciReports) on the induction of ferromagnetism at the interface of BiFeO3 and YBa2Cu3O7.

In this work, Dr. Haraldsen and his collaborators worked to explain the presence of ferromagnetism in a complex oxide heterostructure that should not have that kind of magnetism. Using density functional theory, Drs. Jian-Xin Zhu and Xiao-Dong Wen were able to determine the magnetic energies for various magnetic configurations. Using these energies, Dr. Haraldsen model the configurations and extracted the superexchange couplings between the Fe ions. This analysis showed that the Fe ions at the interface with YBCO produced a ferromagnetic moment. This was then used to explain the magnetic measurements made by Drs. Mi He, C. Panagopoulos, and Elbert E. M. Chia, who used squid magnetometry to investigate the magnetic moment and overall magnetization of various heterostructures.

For further information, please contact J.T. Haraldsen at

Induced Ferromagnetism at BiFeO3/YBa2Cu3OInterfaces

Jian-Xin Zhu, Xiao-Dong Wen, J. T. HaraldsenMi He, C. Panagopoulos Elbert E. M. Chia

Scientific Reports 4, 5368 (2014). 

Friday, June 13, 2014

Undergraduate Research Experience at the Duke University's Free Electron Laser Laboratory

Even Meekins, a junior physics major in the Department of Physics and Astronomy at JMU, took part recently in a 7-day nuclear astrophysics experiment that was successfully performed at the Free Electron Laser Laboratory located on the campus of Duke University in Durham, North Carolina.

Evan is part of  Dr. Adriana Banu's nuclear astrophysics research group here at JMU. Early this year Dr. Banu was funded by the Research Corporation for Science Advancement for her proposed research that aims to contribute to enhancing the current state of fundamental knowledge on a forefront topic in nuclear astrophysics - the nucleosynthesis beyond iron of the rarest stable isotopes in the cosmos, the so-called p-nuclei. More specifically, the research project is focused on constraining the origin of the p-nuclei by measuring key astrophysical photonuclear reaction cross sections with quasi-monochromatic photon beams at Duke University's High Intensity Gamma-ray Source (HIGS) facility, currently the most intense accelerator-driven gamma-ray source in the world.

Evan Meekins and Dr. Adriana Banu during their recent experiment at the Duke University's HIGS facility

Working at HIGS - Evan Meekins in his own words:
"While I love the physics department at JMU, especially the array of materials the physics department has for the students to experiment, the HIGS and TUNL facilities at Duke University are truly awe-inspiring. Being able to experience, albeit only analyzing the data, equipment and electronics that could create high energy photons and evaluate many, if not all, of the possible characteristics of said photons, along with any reactions that they might produce. I also greatly enjoyed the staff working at HIGS; they were very knowledgeable about the physics behind each aspect of the experiment, as well as friendly and interpersonal.  The experiment itself required a good amount of work, in setting up the equipment properly, collecting the data, and analyzing the data, but was all extremely intellectually fulfilling.  I left the HIGS facility feeling greatly more confident in both my ability to perform experimental physics and my understanding of the fundamental physics behind the experiment. I would greatly recommend any physics student to participate in an upper-level experiment, and would cite the HIGS facility at Duke University as a great place to start."

Monday, June 02, 2014

Research presentations at various Academy of Sciences!

On May 15 2014, the JMU Undergraduate Students Harkirat Mann and Brian Lang, doing research with Dr. Scarel, presented  the research on Infrared and thermoelectric power generation in thin atomic layer deposited thermoelectric films” at the 92th Annual Meeting of the Virginia Academy of Science held at the Virginia Commonwealth University in Richmond (VA).  The work was performed in collaboration with J.-P. Niemelä and M. Karppinen of Aalto University in Finland.  The same day, 8 time zones away, at the Russian Academy Of Sciences in Nizhny Novgorod (Russia), Dr. Scarel presented Infrared power generation: basic phenomena and engineering through materials properties”.  In the picture on the right, Dr. Scarel is in Nizhny Novgorod next to the monument to Nikolay Bogolyubov, a famous russian physicist who made important contribution in Statistiacal Mechanics.

Saturday, May 10, 2014

Graduation Day @ JMU: May 10, 2014

CONGRATULATIONS CLASS OF 2014! Best of Luck and Much Success for the Future!!!

Sunday, April 13, 2014

Spring Picnic 2014: Physics Phun in the Sun!

On Sunday April 13th 2014, the @JMU Physics and Astronomy Department celebrated the onset of spring (finally!) with our departmental picnic at Purcell Park. Organized by Dr. C. Constantin, the department provided various foods and drinks for the students, staff, and faculty of the JMU physics and astronomy department. Dr. G. Niculescu (pictured below in his styling apron) cooked hot dogs and hamburgers (both beef and vegetarian), while others brought their favorite dishes and snacks.

After eating and chatting, the competitive spirit caught on and the departmental soccer (futbol) game ensued. Teams captained by Dr. C. Constantin and Dr. Feitosa played energetic game of Romania vs. Brazil!

Everyone had a blast and is looking forward the Fall Picnic...Now get back to work! Finals are coming!

Pictures by Dr. J.T. Haraldsen