Metal-Dependent Antiferromagnetic Interactions in Ba2MCl6 (M2+ = Co, Fe, Mn)

Exploringthe wide array of metal-halide structures offers theopportunity for examining structure-property relationshipsin magnetic solids. Here, we report the magnetism of Ba2CoCl6, which has a crystal structure based on edge-sharingoctahedral transition-metal-halide dimers. Furthermore, the previouslyunreported analogues Ba2FeCl6, Ba2MnCl6, and Ba2MgCl6 are synthesizedand their structures are determined by single-crystal X-ray diffraction.Using Ba2MgCl6 as a diamagnetic control, wemeasure their temperature-dependent magnetizations and heat capacities.Ba2CoCl6 and Ba2FeCl6 exhibitshort-range antiferromagnetic ordering near 1 K, while Ba2MnCl6 displays a transition to long-range magnetic orderingat 0.63 K that is not observed down to 0.5 K in Ba2CoCl6 and Ba2FeCl6. We conclude that theshort-range intradimer and long-range interdimer magnetic orderingtemperatures depend on both the ionic radius and electronic configurationof the transition metal.