Magnetic properties of a metal-organic antiferromagnet Mn(hfipbb)py(H ₂O) _0.5

Mn (hfipbb) py (H2 O)0.5 [H2 hfipbb=4, 4′ -(hexafluoroisopropylidene) bis(benzoic acid), py=pyridine] is a recently discovered metal-organic coordination network. The crystal structure of this compound belongs to a triclinic space group P-1, and the lattice parameters are a=12.988 Å, b=13.296 Å, c=14.644 Å, α=115.13°, Β=95.61°, and γ=101.03°. Two crystallographically independent Mn atoms (Mn1 and Mn2) exist in this structure, and an alternate connection (-Mn1-Mn2-Mn1-Mn2-) through organic units along the x axis leads to a one-dimensional Mn2+ chain. Magnetic susceptibility M (T) H and isothermal magnetization M (H) were measured on single-crystal samples, as well as on powder samples of Mn (hfipbb) py (H2 O)0.5. Antiferromagnetic ordering was observed below a transition temperature of TN =9.0 K. High-temperature susceptibility data for powder samples were fitted to the Curie-Weiss law with θ=-30 K and an effective moment of μeff =5.7 μB, close to what is expected for a free Mn2+ ion. There is small but clear orientation dependence in the susceptibility data for single-crystal samples. The result of isothermal magnetization measured at 2 K is consistent with the interpretation of an antiferromagnetic ground state, and a slope change was seen at a critical field of Hc =18 kG, indicating a field-induced moment reorientation of the Mn2+ ions in this compound.