Magnetic properties of a quasi-one-dimensional antiferromagnet Eu2BiS4

We have synthesized c-axis oriented polycrystals of a Eu-based orthorhombic compound Eu2BiS4 and measured transport, magnetic, and thermal properties down to 1.8 K. The crystal structure of Eu2BiS4 was confirmed by powder x-ray diffraction to be orthorhombic CaFe2O4-type with one-dimensional chains of Eu2+ ions along the c-axis. The electrical resistivity rho increases on cooling from 300 K, which shows that this compound is a semiconductor. Both magnetic susceptibility chi and specific heat C exhibit an obvious peak at T-N = 2.5 K, indicating an antiferromagnetic order. Anisotropic behaviors of isothermal magnetization M and chi below T-N suggest that the magnetic moments align along the c-axis. Moreover, a tail appears in C(T) in the range of T-N < T < 8 K, where chi(T) is reproduced by that calculated with a one-dimensional ferromagnetic Heisenberg model. These behaviors in C(T) and chi(T) are attributed to developed short-range ferromagnetic correlations in the Eu2+ chains.