The effects of nonmagnetic Al impurities on a magnetic bath ${\mathrm{YMnO}}_3$ are studied by magnetization, heat capacity, neutron diffraction, and NMR measurements. Suppression of the Néel order with an increase in the doping rate is evidenced by the heat capacity and $M\text{−}T$ curve, also showing vacancy-induced magnetization. Theory predicts that the vacancies in triangular antiferromagnets release the local frustration partially by a readjustment of the spin directions, which results in a net magnetic moment of $0.04S$ around the impurity site, where $S$ is the single spin moment. Interestingly, our NMR results show that the amplitude of the impurity moment is similar to $S$, which is one order of magnitude larger than a previous prediction. The direction of the impurity moment and neighboring spins generating a hyperfine field at a nonmagnetic impurity site are random. Above $T_N$, the release of frustration due to a spin-vacancy is evidenced by the enhancement of the antiferromagnetic correlation of spins near impurity sites. Based on careful consideration about the structural distortion, we suggest that this huge spin-disorder originates from the magnetic correlation between impurity moments.

• Received 6 June 2020
• Revised 5 November 2020
• Accepted 9 November 2020

DOI:https://doi.org/10.1103/PhysRevB.102.184427