Fractional power law susceptibility and specific heat in low-temperature insulating state of o-TaS ₃

Abstract

PACS. 71.45.Lr -Charge density wave systems. PACS. 75.50.Lk -Spin glasses and other random magnets.Abstract. -Measurements of the magnetic susceptibility and its anisotropy in the quasi-onedimensional system o-TaS3 in its low-T charge density wave (CDW) ground state are reported. Both sets of data reveal below 40 K an extra paramagnetic contribution obeying a power-law temperature dependence χ(T)=AT −0.7 . The fact that the extra term measured previously in specific heat in zero field, ascribed to low-energy CDW excitations, also follows a power law CLEE(0,T)=CT 0.3 , strongly revives the case of random exchange spin chains. Introduced impurities (0.5% Nb) only increase the amplitude C, but do not change essentially the exponent. Within the two-level system (TLS) model, we estimate from the amplitudes A and C that there is one TLS with a spin s=1/2 localized on the chain at the lattice site per cca 900 Ta atoms. We discuss the possibility that it is the charge frozen within a soliton-network below the glass transition Tg ∼40 K determined recently in this system. c EDP Sciences

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