Neutron scattering and mSR studies of spin gap formation in the caged compounds CeT2Al10 (T = Fe, Ru, Os)

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• Dr Devashibhai Adroja (STFC,RAL,ISIS)
• Thursday 29 September 2011, 13:45-15:00
• Theory Library.

If you have a question about this talk, please contact Dr Dimitri M Gangardt.

According to conventional theories of strongly correlated electron systems, the natural consequence of strong hybridization between f-electrons and conduction electrons is the opening of a gap in both charge and spin channels. Despite their importance, there are few experimental observations of such gaps in real materials. Recently, the opening of a spin gap has been reported in the intermetallic compounds CeT2Al10 (T = Ru and Os) below TN = 27-29 K through heat capacity and magnetic susceptibility as well as in the paramagnetic state of CeFe2Al10 through resistivity and NMR measurements. Various theoretical models have been proposed to explain the spin gap formation, for example a spin-Peierls model of Hanzawa for CeRu2Al10. To understand the nature of the spin gap formation in these compounds, we have carried out neutron diffraction, inelastic neutron scattering and mSR studies. Our neutron diffraction and mSR studies reveal a clear sign of long range magnetic ordering in CeRu2Al10 and CeOs2Al10, while CeFe2Al10 does not order down to 50mK. We have found a clear evidence of spin gap formation in the inelastic response of the Ru and Os compounds below their magnetic ordering temperatures. In addition, very broad high energy crystal field excitations have also been uncovered for the Ru and Os compounds. The spin gap energies of the Ru and Os are consistent with a universal scaling that links spin gap energy with Kondo temperature as observed for many Ce and Yb heavy fermion compounds. We will present the temperature and wave vector dependent of the spin gap energy of the Ru and Os compounds that revels the origin of the spin gap. Further, we will present the results on Ce(Ru1-xFex)2Al10 alloys, which clearly reveal the presence of a spin gap (probably spin dimer formation) in the paramagnetic state. These results indicate that the opening of the spin gap in CeT2Al10 (T=Ru and Os) is not only due to single ion anisotropy in the spin wave spectrum, but due to more complex mechanisms. We will compare the spin gap formation in CeT2Al10 with that observed in Kondo semimetals CeT4Sb12 (T=Ru and Os) and dimerised ground state in YbAl3C3.

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