Thermodynamic Properties and DFT Study on Highly Frustrated Cr 3 BO 6 : Coexistence of Spin-Singlets with Long-Range Magnetic Order.

The triangle-based magnetic subsystem of borates with the mineral norbergite structure M 3 BO 6 (M = Fe, Cr, V) makes these compounds unique to investigate rare quantum ground states influenced by strong magnetic frustration. In this work, we investigated the thermal and magnetic properties of Cr 3 BO 6 to find that despite very large negative Weiss temperature Θ = -160.7 K, it orders only at T N = 4.5 K and experiences a spin-flop transition at µ 0 H = 5 T. Density functional theory (DFT) calculations of exchange interaction parameters allow for suggesting the model of magnetic subsystem in chromium borate Cr 3 BO 6 . The results prove the decisive role of magnetic frustration on the formation of long-range order, providing therefore a basis for future study. Both experimental data and first-principles calculations point to the coexistence of chromium spin-singlets with long-range antiferromagnetic order.