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Fulbright Scholars in the Lab James S. Brooks, Florida State University, DMR1005293

Magnetic and conducting co-linear chains stay friendly even at high magnetic fields James S. Brooks, Florida State University, DMR1005293.

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Fulbright Scholars in the Lab James S. Brooks, Florida State University, DMR1005293

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  1. Magnetic and conducting co-linear chains stay friendly even at high magnetic fieldsJames S. Brooks, Florida State University, DMR1005293 • The one-dimensional organic conductor (Per)2[Pt(mnt)2] is unique since it is comprised of co-linear organic conducting perylene and localized spin ½ Pt(mnt)2 chains. The perylene and Pt(mnt)2 chains undergo transitions to insulating charge density wave (CDW) and spin-singlet spin-Peierls (SP) ground states respectively at the same temperature (~ 8 K). This implies that the two order parameters are strongly coupled. • Until recently, the magnetic field dependence of the CDW phase diagram was known only from electrical transport measurements, and the behavior of the SP phase was unknown. Liz Green (FSU-Graduate student) spearheaded an investigation to follow the SP behavior using high field proton (1H) NMR. She discovered that the CDW and SP order parameters remain coupled even in the high magnetic field limit.[1] • Her work raises theoretical and experimental questions about how the two order parameters are coupled, and how they will interact when the spin chain is completely polarized near 45 T. Plans are underway for a further higher field investigation. Comparison of magnetic-field-dependent phase boundaries of (Per)2[Pt(mnt)2] determined from electrical transport and torque measurements, 1H NMR measurements, and mean field predictions for TCDW and TSP. TSP follows the experimental TCDW boundary, not the mean field prediction with no order parameter coupling. [1] E.L. Green, et al., Interaction of magnetic field-dependent Peierls and spin Peierlsground states in (Per)2[Pt(mnt)2], PRB Rapid Com.,in press (2011).

  2. Fulbright Scholars in the LabJames S. Brooks, Florida State University, DMR1005293 Dr. Wasan Rashid Saleh, College of Science, University of Baghdad, Iraq • Our lab hosted two Fulbright Scholars this year who worked very closely with the students in the group. • Dr. Wasan Saleh from Baghdad University developed strain sensitive sensors based on carbon nanotube mats that could be taped to the wrist to monitor the human heart pulse rate under different metabolic conditions. • Dr. Danica Krstovska, who is a theorist by training, worked with our group to do both experiments and theoretical treatments of the Seebeck and Nernst effects in the low dimensional organic conductor • a-(BEDT-TTF)2KHg(SCN)4 in high (and tilted) magnetic fields. Carbon nanotube sensors for human heart pulse measurements. Dr. Danica Krstovska Ss. Cyril-Methodius University, Macedonia Angular dependent magnetothermopower of a-(ET)2KHg(SCN)4, D. Krstovska, E. Steven, E. S. Choi, and J. S. Brooks, Low Temp. Phys. (FizikaNizkikhTemperatur), in press (2011).

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