Quaternary antiferromagnetic Ba2BiFeS5 with isolated FeS4 tetrahedra**Project supported by the National Key Research and Development Program of China (Grant No. 2016YFA0300504), the National Natural Science Foundation of China (Grant Nos. 11574394, 11774423, and 11822412), the Fundamental Research Funds for the Central Universities, and the Research Funds of Renmin University of China (RUC) (Grant Nos. 15XNLQ07, 18XNLG14, and 19XNLG17).

Abstract

We report the detailed physical properties of quaternary compound Ba2BiFeS5 with the key structural ingredient of isolated FeS4 tetrahedra. Magnetization and heat capacity measurements clearly indicate that Ba2BiFeS5 has a paramagnetic to antiferromagnetic transition at about 30 K. The calculated magnetic entropy above ordering temperature is much smaller than theoretical value for high-spin Fe3+ ion with S = 5/2, implying the possible short-range antiferromagnetic fluctuation in Ba2BiFeS5.