Quasi-two-dimensional magnetism in spin-1/2 square lattice compound Cu[C6H2(COO)4][H3N-(CH2)2-NH3]•3H2O

We report the crystal growth and structural and magnetic properties of quasi-two-dimensional S = 1/2 quantum magnet Cu[C6H2(COO)(4)][H3N-(CH2)(2)-NH3] center dot 3H(2)O. It is found to crystallize in a monoclinic structure with space group C2/m. The CuO4 plaquettes are connected into a two-dimensional framework in the ab-plane through the anions of [C6H2(COO)(4)](4-) (pyromellitic acid). The [H3N-(CH2)(2)-NH3](2+)center dot 3H(2)O groups are located between the layers and provide a weak interlayer connection via hydrogen (H center dot center dot center dot O) bonds. The temperature-dependent magnetic susceptibility is well described by S = 1/2 frustrated square lattice (J(1) - J(2)) model with nearest-neighbor interaction J(1)/k(B) similar or equal to 5.37K and next-nearest-neighbor interaction J(2)/k(B) similar or equal to -0.37K. Our analysis using frustrated rectangular lattice (J(1a, b) - J(2)) model also confirms almost isotropic nearest-neighbour interactions (J(1a)/k(B) similar or equal to 5.31K and J(1b)/k(B) similar or equal to 5.38K) in the ab-plane and J(2)/k(B) similar or equal to -0.24K. Further, the isothermal magnetization at T = 1.9K is also well described by a non-frustrated square lattice model with J(1)/k(B) similar or equal to 5.2K. Based on the J(2)/J(1) ratio, the compound can be placed in the Neel antiferromagnetic state of the J(1) - J(2) phase diagram. No signature of magnetic long-range order is detected down to 2K. Copyright (C) 2021 EPLA