Chloride Reduction of Mn3+in Mild Hydrothermal Synthesis of a Charge Ordered Defect Pyrochlore, CsMn2+Mn3+F6, a Canted Antiferromagnet with a Hard Ferromagnetic Component

Geometrically frustrated systems play an important role in studying new physical phenomena and unconventional thermodynamics. Charge ordered defect pyrochlores AM2+M3+F6offer a convenient platform for probing the interplay between electron distribution over M2+and M3+sites and structural distortions; however, they are limited to compounds with M2+/3+= V, Fe, Ni, and Cu due to difficulties in the simultaneous stabilization of other 3d elements in the +2 and +3 oxidation states. Herein, we employ Cl–anions under hydrothermal conditions for the mild reduction of Mn2O3in concentrated HF to obtain the CsMn2+Mn3+F6composition as a phase pure sample and study its properties. The magnetism of CsMn2F6was characterized by measuring the magnetic susceptibility and isothermal magnetization data, and a magnetic transition to a canted antiferromagnet state was found at 24.1 K. We determined the magnetic structure of CsMn2F6using powder neutron diffraction, which revealed successive long-range ordering of the Mn2+and Mn3+sites that is accompanied by a second transition. The role and strength of magnetic exchange interactions were characterized using DFT calculations.