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COLLOQUIUM OF THE COMPUTATIONAL MATERIALS SCIENCE CENTER
AND
THE DEPARTMENT OF COMPUTATIONAL & DATA SCIENCES
(CSI 898-Sec 001)
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Understanding and controlling the magnetic exchange of novel materials
James Glasbrenner
Department of Computational and Data Sciences, and
Computational Materials Science Center, George Mason University, Fairfax, VA
The behavior of electrons in materials underpins key materials properties,
which means that computing and understanding the electronic structure of
various materials systems is of vital importance. These computations are,
nowadays, often performed using density functional theory (DFT), a
first-principles methodology that is an important tool in the computational
materials scientist's toolbox. One of the materials properties that is
accessible via DFT is magnetism, and DFT can be used to study the magnetic
interaction between electrons (called the exchange interaction) in a
material. This involves constructing models such as the Heisenberg model and
mapping DFT calculations onto it, which allows one to understand how tuning
different features impacts important parameters such as the critical
temperature and the stability of magnetic ground state. This approach to
studying magnetic materials is of particular appeal in the spin electronics
field, where the encoding and processing information using the magnetic states
of electrons is of central importance.
In this talk I will: 1) introduce the basic concepts of computational materials
science using DFT in an accessible manner, and 2) present calculations on two
different materials where I used DFT in conjunction with modeling to analyze
the magnetic interactions. The first presented material will be the dilute
magnetic semiconductor (Ba, K)(Zn, Mn)2As2, which exhibits ferromagnetism when
a small amount of manganese and potassium are substituted into the material,
and where changing the relative quantity of potassium influences the strength
of the magnetic interactions. The second presented material is MnAu2, a
magnetic metal that has a cork-screw noncollinear magnetic ground state which
can be tuned in intriguing ways using pressure and chemical substitution. Using
modeling in combination with DFT, I will show how we are able to understand the
nature of the microscopic magnetic interactions in each material and that the
microscopic mechanisms driving the the magnetic interactions in both compounds
is the same. These results can then be used to resolve several experimental
questions, one of which had gone unaddressed for several decades.
September 19, 2016
4:30 pm
Exploratory Hall, room 3301
Fairfax Campus
Refreshments will be served at 4:15 PM.
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Find the schedule at http://www.cmasc.gmu.edu/seminars.htm