Case Study Of Bilayered Spin-1/2 Square Lattice Compound Vo(Hcoo)(2) Center Dot (H2o)

We present the synthesis and a detailed investigation of structural and magnetic properties of polycrystalline VO(HCOO)(2) center dot (H2O) by means of x-ray diffraction, magnetic susceptibility, high-field magnetization, heat capacity, and electron-spin-resonance measurements. The compound crystallizes in an orthorhombic structure with space group Pcca. The crystal lattice features distorted VO6 octahedra connected via HCOO linkers (formate anions), forming a two-dimensional square lattice network with a bilayered structure. Analysis of magnetic susceptibility, high-field magnetization, and heat capacity data in terms of the frustrated square lattice model unambiguously establish the quasi-two-dimensional nature of the compound with nearest-neighbor interaction J(1)/k(B) similar or equal to 11.7 K and next-nearest-neighbor interaction J(2)/k(B) similar or equal to 0.02 K. A Neel antiferromagnetic ordering sets in at T-N similar or equal to 1.1 K. The ratio theta(CW)/T-N similar or equal to 10.9 reflects excellent two-dimensionality of the spin-lattice in the compound. A strong in-plane anisotropy is inferred from the linear increase of T-N with magnetic field, consistent with the structural data.