Selective Octahedral Accommodation of Cr3+ and Weak Magnetic Connectivity in the Sugilite Analogue KNa2Cr2Li3Si12O30

Abstract We report the synthesis of the Cr analogue of sugilite, KNa2Cr2Li3Si12O30, in the milarite-type framework. Rietveld refinement of a composition-conserving antisite model gives x = 0.0024(18) in KNa2[Cr2-xLix][Li3-xCrx]Si12O30, corresponding to a T2-site Cr occupancy of 0.0008(6). X-ray MEM analysis shows no detectable Cr-like density at T2. Magnetic susceptibility indicates weak antiferromagnetic interactions with θW = −4.78(7) K and no ordering above 1.8 K.