Robustness of the spin liquid state with respect to magnetic dilution in the bilayer kagome material Ca10Cr7 O28

Abstract

Recently, the bilayer kagome lattice material Ca10Cr7O28 has been shown to be a quasi-two-dimensional quantum spin liquid (QSL) where the frustration arises from a balance between competing ferromagnetic and antiferromagnetic exchange within a bilayer. In an attempt to understand what happens when this balance is disturbed, we present a magnetic dilution study. Specifically, we have synthesized Ca10(Cr1−xVx)7O28 (0≤x≤0.5) where magnetic Cr5+ (S=1/2) is partially replaced by nonmagnetic V5+ (S=0). We also synthesized the fully nonmagnetic isostructural material Ca10V7O27.5. We report a detailed structural, magnetic and heat capacity study on these materials. A monotonic increase in the unit cell parameters is found for the Ca10(Cr1−xVx)7O28 materials with increasing x. An order of magnitude decrease in the Curie-Weiss temperature from 4 to 0.5 K is found for the partial V substituted samples, which indicates a relative increase in antiferromagnetic exchange with increase in V content. However, despite this change in the relative balance in the exchange interactions and the large disorder introduced, no magnetic ordering or spin-glass state is observed down to 2 K in the V substituted samples. The QSL state of the parent compound thus seems surprisingly robust against these large perturbations.