27. 9. 2012. Seminar: Emil Bozin

Thursday 27 September 2012 12PM
IPB Library

Dr Emil Bozin, BNL

Charting the fluctuating Ir4+-dimer map across the phase diagram of Cu(Ir1-xCrx)2S4 (0≤x≤0.6)

Elucidating the role of fluctuations in systems with competing interactions, such as Cu(Ir1-xCrx)2S4, enables comprehensive understanding of their physical properties. While CuIr2S4 exhibits complex behavior with metal-insulator transition accompanied by charge ordering and Ir4+-spin-dimerization at 226K, CuCr2S4 displays ferromagnetic metallic behavior (TC~377K) understood within the double exchange model. Intermediate composition range sees suppression of end-member properties, with broad features observed in susceptibility around 180 K attributed to Cr3+ low-spin to high-spin crossover[1].

Robust fluctuating Ir4+ dimers are detected and their evolution examined across the phase diagram by the X-ray atomic pair distribution function method. Although their long range order is destroyed already by x~0.05, Ir4+ dimers exist locally at low temperature at all compositions studied. Detailed account will be provided of the Cr-doping and temperature dependence of the local dimers, and characteristic length-scale on which they are observable estimated. Fluctuating dimers disappear on heating, for intermediate compositions at temperatures above 180 K.

[1] R. Endoh et al., Phys. Rev. B 68, 115106 (2003).