"Physics of Complex Materials"

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Date/Time:Monday, 11 Mar 2013 from 4:10 pm to 5:00 pm
Location:Physics 0005
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Dr. Evgenii Levin (Ames Lab/US DOE/ISU)

Abstract: A number of complex solid state systems have been studied demonstrating my work in the area of condensed matter and materials physics. These systems include: (i) RM2X2 intermetallic compounds (R = rare earth, M = transition element, X = Si, Ge), (ii) Gd5Ge4-based materials, (iii) micro- and nano-scale materials containing paramagnetic ions, and (iv) complex thermoelectric tellurides. Several interesting phenomena were found, e.g., Kondo-like behavior due to Eu in zero magnetic field and due to Ce induced by a magnetic field, antiferromagnet to ferromagnet transformations induced by a magnetic field, temperature, or composition, and enhancement of thermopower by doping tellurides with rare earth. Most recently, complex tellurides are being used as a model system to study the effect of the composition on thermoelectric phenomenon. 125Te nuclear magnetic resonance allows us to obtain free charge carrier concentration for tellurides. An energy filtering model is used to explain the enhancement of thermopower due to replacement of Ge in GeTe by [Ag+Sb] and rare-earths atoms. Better fundamental understanding of thermoelectric tellurides opens a new pass for designing more efficient thermoelectric materials.