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MA: Magnetismus

MA 20: Poster: Films(1-36) Transp(37-56) Ex.Bias(57-67) Spindyn(68-80) Micromag(81-95) Particle(96-109) Imag.+Surface(110-113) Spinelectr(114-122) Theory+Micromag(123-131) Spinstr+Aniso(132-142) MagMat(143-156) Meas(157,158) MolMag+Kondo(159-162) Postdead(163-)

MA 20.9: Poster

Dienstag, 28. März 2006, 15:15–19:15, P1

Electronic structure and transport properties of Ce₂Rh₂XAl₉ (X=Co,Ir,Pd) — •Jerzy Goraus and Andrzej Slebarski — Institute of Physics, University of Silesia

We have investigated transport properties and electronic structure of Ce₂Rh₂XAl₉ (X=Co,Pd,Ir) compounds which are formed by substitution of one Rh atomic site in Ce₂Rh₃Al₉. Specific heat measurements showed moderate γ value of 0.4J/molK² for X=(Co,Rh) and a higher one for X=(Ir,Pd) of about 1.1J/molK². XPS Ce-3d and Ce-4d spectra showed a clear mixed valence behaviour, confirmed also by the TB-LMTO-ASA and FP-LAPW band structure calculations. For X=Ir,Co and Rh we obtained a nonmagnetic semiconducting ground state from TB-LMTO calculations, whereas FP-LAPW gave us magnetic ground state for all compounds with pseudogap on Fermi level for one spin direction. Our susceptibility measurements show that no long range magnetic ordering is present for these compounds down to 2K, however for X=Pd,Ir we suspect spinglass transition with freezing temperature ∼ 5K. Electrical resistivity exhibits Kondo lattice behaviour for X=Co,Pd whereas for X=Ir we have metallic-like shape. Lack of activated behaviour in electrical resistivity we explain by an atomic disorder, however for temperatures similar to calculated gap there is present an anomaly in ρ(T). Calculations for reduced and increased lattice constants doesn’t lead to vanishing of gap in LMTO calculations.