Anisotropy-Tuned Magnetic Order in Pyrochlore Iridates

E. Lefrançois, V. Simonet, R. Ballou, E. Lhotel, A. Hadj-Azzem, Stéphanie Kodjikian, P. Léjay, Pascal Manuel, D. D. Khalyavin, L. C. Chapon

Abstract

The magnetic behavior of polycrystalline samples of Er$_2$Ir$_2$O$_7$ and Tb$_2$Ir$_2$O$_7$ pyrochlores is studied by magnetization measurements and neutron diffraction. Both compounds undergo a magnetic transition at 140 and 130 K respectively, associated with an ordering of the Ir sublattice, signaled by thermomagnetic hysteresis. In Tb$_2$Ir$_2$O$_7$, we show that the Ir molecular field leads the Tb magnetic moments to order below 40 K in the all-in/all-out magnetic arrangement. No sign of magnetic long range order on the Er sublattice is evidenced in Er$_2$Ir$_2$O$_7$ down to 0.6 K where a spin freezing is detected. These contrasting behaviors result from the competition between the Ir molecular field and the different single-ion anisotropy of the rare-earths on which it is acting. Additionally, this strongly supports the all-in/all-out iridium magnetic order.

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• Physical Review Letters - View
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