Abstrakt
Single crystals of YbPt2Si2 and Yb2Pt3Si5 have been prepared by solvent growth method with Sn flux, characterized by X-ray diffraction and by EDX microprobe analysis and investigated by measurement of magnetization, specific heat and electrical resistivity as functions of temperature and magnetic field. YbPt2Si2 (Yb2Pt3Si5) crystalizes in the tetragonal CaBe2Ge2-type (orthorhombic U2Co3Si5-type) structure.
Both compounds exhibit metallic resistivity behavior without visible anomaly, which could be connected with onset of magnetic ordering. Neither the specific heat shows any sign of magnetic ordering down to 0.5 K.
The corresponding temperature dependences of the magnetic susceptibility of both compounds behave qualitatively similar, which is reminiscent of spin fluctuation behavior: a broad maximum at high temperatures, a shallow minimum at lower temperatures, followed by an upturn with further cooling the crystal, which can be suppressed by applying a sufficient magnetic field. The rather low values of the gamma-coefficients of the specific heat (similar to 25 divided by 35 mJ.mol.K-2) do not support the mixed valence scenario discussed in literature for YbPt2Si2.