Influence of Structure and Doping on Frustration in Low-Dimensional Coordination Polymers

Magnetic materials are good candidates for cooling applications due to the magnetocaloric effect, potentially replacing conventional gas compression/expansion refrigeration in future technologies. In particular, magnetic coordination polymers and metal-organic frameworks have attracted attention due to their flexible design. When low-dimensional motifs and geometric frustration are present, these materials show promising magnetocaloric properties at low and ultra-low temperatures, which is particularly useful for replacing conventional cryogenics, including He, an increasingly scarce resource. Probing the magnetic interactions is important for understanding the properties they can exhibit and can provide further understating into how these properties can be enhanced. This thesis explores the effects of modifying the structure of well-known lanthanide-based frustrated frameworks, as well as doping these. A complex 2D-layered framework exhibiting 2D magnetism, [Li(C2O4)]2[Co5(OH)8], has been studied as well, with its magnetic structure determined at 8 K. The nuclear structures and magnetic properties of the materials have been investigated with a combination of techniques, including x-ray and neutron diffraction, combined with Rietveld refinements of the obtained patterns.