Neutron diffraction and specific heat studies on the magnetic ordering in the [FeII (Δ) FeII (Λ) (ox)2 (Phen)2] n molecular magnet

The magnetic characteristics of the molecular magnet [FeII (Δ) FeII (Λ) (ox)2 (Phen)2] n, having chemical formula C28 H16 Fe2 N4 O8 for unity, has been studied by magnetization, neutron diffraction, and field-dependent specific heat-measurements. In the high-temperature regime (T> Tm), the one-dimensional Ising chain model with alternate Landé factors is applied to describe its quasiferrimagnetic behavior as temperature approaches Tm. In the low-temperature region (T< Tm), the increase of interchain interactions gives rise to long-range magnetic ordering as indicated by an anomaly in specific heat. Furthermore, an intrinsic antiparallel alignment of spins with a net ferrimagnetic structure is deduced from neutron diffraction study. The field-dependent λ -type anomaly of specific heat indicates that applying a magnetic field raises magnetic ordering temperature. An additional small anomaly in specific heat is also seen below Tm, which could be due to the zero-field splitting caused by the internal crystal field.