Hamburg 2001 – scientific programme

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TT: Tiefe Temperaturen

TT 6: Postersitzung I: Josephsonkontakte und SQUIDs, Supraleitung: Theorie, Korrelierte Elektronen, Niederdimensionale Systeme, Magnetotransport, Quantenhalleffekt, Kohlenstoff-Nanoröhrchen, Quantenflüssigkeiten

TT 6.56: Poster

Monday, March 26, 2001, 14:30–17:00, Rang S\ 3

Magnetic anisotropy of the low-T specific heat and ac-susceptibility of one-dimensional S=1/2 Heisenberg antiferromagnet Yb₄As₃ — •H. Aoki¹, T. Cichorek¹, P. Gegenwart¹, F. Steglich¹, and A. Ochiai² — ¹MPI for Chemical Physics of Solids, Dresden, Germany — ²Tohoku University, Sendai, Japan

One of the unique properties of the rare-earth compound Yb₄As₃ is the charge-ordering transition at T_co=293 K which leads to the formation of one-dimentional Yb³⁺ (S=1/2) chains. Below T_co the smaller Yb³⁺ ions order along one of the possible four space diagonals which usually results in the formation of a multi-domain structure. The low-T specific heat and susceptibility of Yb₄As₃ are well described by quantum sine-Gordon soliton model of a one-dimensional S=1/2 Heisenberg antiferromagnet. The existence of the antiferromagnetic S=1/2 Heisenberg chains at low temperature was clearly confirmed via inelastic neutron-scattering experiments. Recently, our detailed investigation of the specific heat and ac-susceptibility shows another weak magnetic interaction, which occurs around 150 mK due to interchain-coupling effects. Its behavior seems to be very similar to that expected for spin glasses.

In order to check the validity of the theoretical model we studied the anisotropy of the low-T properties of Yb₄As₃ on single-domain samples in magnetic fields up to 10 T. Note that solitons exist only for fields perpendicular to the spin chains. A preferential orientation of the domains was induced by the application of uniaxial stress prior to cooling through T_co. Thereby, we could also investigate the influence of different domain configurations on the spin-glass like anomaly in Yb₄As₃.