The following is a pre-recorded version of my invited talk for the 2015 APS March Meeting in San Antonio, TX. My talk was in Session S31, and was delivered on March 5th, 2015 at 8:36 AM. The abstract for the talk can be found here: http://meeting.aps.org/Meeting/MAR15/Session/S31.4
The talk discusses the theory of the exciting new class of dilute magnetic semiconductors that are isostructural to a specific subset of iron-based superconductors. The materials are well suited to manipulation through doping, as magnetic and charge doping are handled in separate sublattices. The physics of these materials are transparent, and thus are suitable to theoretical analysis using density functional theory calculations. Using the material (Ba, K)(Zn, Mn)_2As_2, I explain in the talk how we performed and analyzed these calculations, and concluded that the magnetic interaction in this system is a combination of a superexchange interaction and an effective double exchange interaction. This implies that the magnetic interaction itself is tunable, and paves the way for increasing the system's Curie temperature. In addition, we also explain using a statistical model why, in experiment, the directly observed magnetization per Mn is strongly reduced from the 5 Bohr magnetons obtained from high-temperature susceptibility measurements.
The talk is based on my Rapid Communication published in Physical Review B. The abstract for the paper is here: http://link.aps.org/doi/10.1103/PhysRevB.90.140403. If you do not have access to Physical Review B, a copy of the article can be downloaded from my personal website, http://jkglasbrenner.com, under the publications/papers section.