Higher-Magnesium-Doping Effects on the Singlet Ground State of the Shastry-Sutherland SrCu(BO).

Doping of quantum antiferromagnets is an established approach to investigate the robustness of their ground state against the competing phases. Predictions of doping effects on the ground state of the Shastry-Sutherland dimer model are here verified experimentally on Mg-doped SrCu(BO). A partial incorporation of Mg on the Cu site in the SrCu(BO) structure leads to a subtle but systematic lattice expansion with the increasing Mg-doping concentration, which is accompanied by a slight decrease in the spin gap, the Curie-Weiss temperature, and the peak temperature of the susceptibility.