Structure and unusual magnetic properties of YbMn_0.17Si_1.88

Abstract

YbMn_0.17Si_1.88 was synthesized from the reaction of ytterbium, manganese, and silicon using indium as a flux. The average structure of YbMn_0.17Si_1.88 was refined in the monoclinic space group P2₁, with a = 4.0107(8) Å, b = 3.8380(8) Å, c = 14.458(3) Å, β = 97.97(3)°, R1/wR2 = 0.0296/0.0720. The structure can be described as the intergrowth of three AlB₂-type layers and one BaAl₄-type layer. Magnetic susceptibility measurements suggest that the ytterbium atoms in YbMn_xSi_2-x exist in a mixed valent or intermediate valent state. YbMn_0.17Si_1.88 shows weak antiferromagnetic ordering below ∼4.5 K. The magnetic interactions between the Mn and Yb atoms in YbMn_0.17Si_1.88 are evident from the magnetic susceptibility measurements performed at low field. A negative magnetization is observed on warming and a positive magnetization on cooling. The heat capacity data suggest moderate heavy fermion behavior.