The search for new spin-liquid materials - synthesis of kagome and pyrochlore fluoride magnetics

This thesis focuses on the synthesis and characterization of a new AA′ B2F7-type pyrochlore fluoride family, NaCdB2F7 (B = Mn, Fe, Co, Ni, Cu, Zn) predicted by a cal- culated pyrochlore structural tolerance factor, as well as the synthesis of new kagome flu- orides Na3CdCo3AlF14, Rb2SnCo3F12 and Cs2ZrCo3F12, aiming to expand the knowledge about the frustrated pyrochlore and kagome antiferromagnets. The synthesis techniques included solid-state reactions, laser floating zone melting and melt crystallization. All pyrochlore fluorides were successfully synthesized, although only B = Zn, Co, Mn and Ni as phase-pure single crystals. PXRD refinements confirmed the Fd̄3m structure in all synthesized pyrochlores, while SCXRD showed full Na/Cd disorder on the A-site and no A/B intersite mixing in the Co pyrochlore. Magnetization measurements revealed domi- nant antiferromagnetic interactions evidenced by large negative Curie-Weiss temperatures (from -38 K in Mn to -108 K in Co), with a spin-freezing transition below 4 K in B = Co, Mn and Ni, evidenced by further AC susceptibility and heat capacity measurements in Co and Mn. Cu showed no spin freezing down to the lowest-measured temperature, 1.8 K, implying a very large magnetic frustration. Fe has not been measured due to the large impurity content. The..