Long-range antiferromagnetic order and possible field induced spin-flop transition in BiMnVO5

We report the bulk magnetic characterization of a dimeric chain material, BiMnVO5, by means of magnetic susceptibility, magnetization and heat capacity measurements. Our results provide compelling evidence of an antiferromagnetic (AFM) transition at (T N) ~ 11.5 K. Moreover, the magnetic entropy change in zero field saturates to 14.6 J mol−1 K−1 which is close to the total spin entropy of Mn2+. The development of long-range magnetic order in this chain material demonstrates the interplay of strong intra-chain and inter-chain interactions between the dimers, in addition to the intra-dimer interaction. Low-temperature (T < T N) heat capacity data indicate the presence of a gap (Δ/k B ≈ 5 K) in the spin excitations. Furthermore, the isothermal magnetization below T N shows an anomaly in the slope between 30 and 40 kOe which is suggestive of a spin-flop transition. Such a low-field spin-flop transition and gapped spin wave excitations may be attributed to the presence of (weak) magnetic anisotropy in this material. We attempt to construct a phase diagram in the magnetic field-temperature plane by extracting data from in-field heat capacity and isothermal magnetization measurements.