2005/06/24 by Yu. N. Shvachko, Shvachko, Yu. N., D. V. Starichenko +7
Physics and Astronomy · #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #cond-mat.mtrl-sci
paper · pdf · doi:10.48550/arxiv.cond-mat/0506634
arxiv created 2005/06/24 · arxiv updated 2009/12/01
Layered organic conductors (BEDO-TTF)2ReO4*H2O (metal) and (BEDT-TTF)xDy(NO3)z (paramagnetic insulator) are studied by CW-EPR and SQUID methods. A correlation in resonance and transport properties of both compounds is attributed to a similar mechanism of fine anion ordering (AO) at TAO=200 K. Due to the hydrogen bonds motif the small configuration changes in anion sub-lattice bring a profound effect on electronic properties. It is shown that the spin system of (BEDO-TTF)2ReO4*H2O consists of a fraction of delocalized pi-type holes (Iepr=n(eF)), Iepr(300K)=1,62*10^(-4) emu/mol and antiferromagnetically correlated local moments S=1/2, chip(300K)=1,86*10^(-3) emu/mol. The phase transition Me-Me at TAO=203 K is detected by paramagnetic relaxation and resisitivity but it is not observed in spin susceptibility. Fraction of delocalized holes gradually decreases by factor 2 at cooling down to 100 K, whereas contribution from local moments reaches maximum at 50 K and falls to zero at 14 K. However, at 2 K total spin susceptibility is fully recovered approaching 6*10^(-2) emu/mol. In turn, (BEDT-TTF)xDy(NO3)z does not have solvent bridges (H2O) between neighboring anions and the disorder in anion layer converts this compound into paramagnetic insulator. Moreover, the anion metal-complexes Dy(NO3)zn(-) contain magnetic ions Dy3(+). Nonetheless, the phase transition of similar origin is also detected at T=197 K by ESR and resistivity measurements. Two spin sub-systems co-exist in this compound: hopping local moments S=1/2 (BEDT-TTF^(+)), Iepr(300K)=6,3*10^(-4) emu/mol and strongly localized 4f9-electrons, J=15/2 (Dy3(+)), chip(300K)=4*10^(-2) emu/mol.