Structural, thermal and magnetic characterization of the manganese oxyhalide layered perovskite, (MnCl)LaNb2O7

Mn-Cl sheets were inserted into the perovskite blocks of a double-layered Dion-Jacobson compound by ion exchange at low temperature (390°C). The Rietveld structural analysis of X-ray powder diffraction data (P4/mmm) indicates that the product, (MnCl)LaNb₂O₇, has the manganese coordinated by two apical oxygens from the perovskite layers and four in-plane chlorines within the interlayer space. On heating, this compound exhibits an exothermic transition between 650°C and 750°C that is consistent with metastability. Magnetic characterization shows Curie-Weiss behavior at higher temperatures (>200 K) with a magnetic moment corresponding to the presence of high-spin Mn²⁺ ion (S=5/2). At lower temperatures, antiferromagnetic interactions become significant and the broad maximum at 63 K reveals the 2-D character of the magnetic behavior. The susceptibility data, fit with the high temperature expansion for a Heisenberg square planar system, show a negative exchange interaction of J/k=−3.77 K.