Magnetic properties of manganese based one-dimensional spin chains

We have correlated the structure-property relationship of three manganese-based inorganic-organic hybrid structures. Compound 1, [Mn-2(OH-BDC)(2)(DMF)(3)] (where BDC = 1,4-benzene dicarboxylic acid and DMF = N,N'-dimethylformamide), contains Mn2O11 dimers as secondary building units (SBUs), which are connected by carboxylate anions forming Mn-O-C-O-Mn chains. Compound 2, [Mn-2(BDC)(2)(DMF)(2)], contains Mn4O20 clusters as SBUs, which also form Mn-O-C-O-Mn chains. In compound 3, [Mn-3(BDC)(3)(DEF)(2)] (where DEF = N,N'-diethylformamide), the distorted MnO6 octahedra are linked to form a one-dimensional chain with Mn-O-Mn connectivity. The magnetic properties were investigated by means of magnetization and heat capacity measurements. The temperature dependent magnetic susceptibility of all the three compounds could be nicely fitted using a one-dimensional S = 5/2 Heisenberg antiferromagnetic chain model and the value of intra-chain exchange coupling (J/k(B)) between Mn2+ ions was estimated to be similar to 1.1 K, similar to 0.7 K, and similar to 0.46 K for compounds 1, 2, and 3, respectively. Compound 1 does not undergo any magnetic long-range-order down to 2 K while compounds 2 and 3 undergo long-range magnetic order at T-N approximate to 4.2 K and approximate to 4.3 K, respectively, which are of spin-glass type. From the values of J/k(B) and T-N the inter-chain coupling (J(perpendicular to)/k(B)) was calculated to be about 0.1J/k(B) for both compounds 2 and 3, respectively.