Revealing the degree of magnetic frustration by non-magnetic impurities

Abstract

Imaging the magnetic fields around a non-magnetic impurity can provide a clear benchmark for quantifying the degree of magnetic frustration. Focusing on the strongly frustrated J1–J2 model and the spatially anisotropic J1a–J1b–J2 model, very distinct low-energy behavior reflects different levels of magnetic frustration. In the J1–J2 model, bound magnons appear trapped near the impurity in the ground state and strongly reduce the ordered moments for sites proximal to the impurity. In contrast, local moments in the J1a–J1b–J2 model are enhanced on the impurity neighboring sites. These theoretical predictions can be probed by experiments such as nuclear magnetic resonance and scanning tunneling microscopy, and the results can help us to elucidate the role of frustration in antiferromagnets and help narrow the possible models for understanding magnetism in iron pnictides.