Kagome, a distinctive Japanese basket weave pattern, is used as a specialized term for a two-dimensional lattice made of corner shared triangles of magnetic ions. Antiferromagnets featuring Kagome structure (KAFM) are a canonical example of geometrically frustrated magnetic (GFM) systems under extensive studies. A structurally perfect, GFM lattice has long been sought since it presents an ideal construct for the model study relevant to the unusual physics of strongly correlated spin systems such as resonating-valence-bond state proposed by Anderson in high Tc superconductivity. With GFM systems, a spin cannot simultaneously minimize magnetic interactions with neighboring spins, but instead, fluctuates between many different spin configurations. Theoretically, this highly degenerate ground state cannot be illustrated by a single minimized solution to the Hamiltonian for the antiferromagnetic spin interactions. This quantum spin fluctuation has been thought to suppress long-range magnetic order (LRMO) and is often complemented by exotic ground state phenomena such as spin-glass, spin-ice and spin-liquid behaviors. Structurally, a perfect GFM crystal for model study must possess trigonal (or hexagonal) symmetry inherent of the space groups such as P63/mmc (no. 194). Prior to this study, the search for ideal KAFM compounds has mostly been done via hydrothermal methods. This presentation reports an ideal class of kagome solids, manganese(III) oxo-germanates synthesized via high-temperature (> 700 oC), flux-growth methods. AMn3O2(Ge2O7), where A = K (1 ) and for comparative studies, K0.35(1)Rb0.65(1) (2 ) as well as solid solution were synthesized. The initial magnetic study shows that 1  has established LRMO that is partially suppressed at higher magnetic fields and as shown in 2 , can be interrupted via random K+/Rb+ cation substitution. This family of compounds opens up exciting possibilities in model studies by tweaking factors that govern the spin state of magnetic frustration via controlled chemical modifications which are difficult to achieve through hydrothermal methods.

KMn3O2(Ge2O7): an S = 2 magnetic insulator featuring pillared kagome lattice

248th National Meeting (2014)

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