| Abstract: | We report the detailed physical properties of quaternary compound Ba_2BiFeS_5 with the key structural ingredient of isolated FeS_4 tetrahedra. Magnetization and heat capacity measurements clearly indicate that Ba_2BiFeS_5 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 Fe~(3+) ion with S = 5/2, implying the possible short-range antiferromagnetic fluctuation in Ba_2BiFeS_5. |
