We report neutron diffraction measurements of the magnetic structures in two pyrochlore iridates, Yb2Ir2O7 and Lu2Ir2O7. Both samples exhibit the all-in-all-out magnetic structure on the Ir4+ sites below TN~ 150,K, with a low temperature moment of around 0.45 muB/Ir. Below 2\,K, the Yb moments in Yb2Ir2O7 begin to order ferromagnetically. However, even at 40 mK the ordered moment is only 0.57(3)muB/Yb, well below the saturated moment of the ground state doublet of Yb3+ (1.9 muB/Yb), deduced from magnetization measurements and from a refined model of the crystal field environment, and also significantly smaller than the ordered moment of Yb in Yb2Ti2O7 (0.9 muB/Yb). A mean-field analysis shows that the reduced moment on Yb is a consequence of enhanced phase competition caused by coupling to the all-in-all-out magnetic order on the Ir sublattice.
@article{arxiv.1909.07819,
title = {Strong quantum fluctuations due to competition between magnetic phases in a pyrochlore iridate},
author = {Henrik Jacobsen and Cameron D. Dashwood and Elsa Lhotel and Dmitry Khalyavin and Pascal Manuel and Ross Stewart and Dharmalingam Prabhakaran and Desmond F. McMorrow and Andrew. T. Boothroyd},
journal= {arXiv preprint arXiv:1909.07819},
year = {2020}
}