Revisiting spin ice physics in the ferromagnetic Ising pyrochlore Pr${}_2$Sn${}_2$O${}_7$

Abstract

Pyrochlore materials are characterized by their hallmark network of corner-sharing rare-earth tetrahedra, which can produce a wide array of complex magnetic ground states. Ferromagnetic Ising pyrochlores often obey the "two-in-two-out" spin ice rules, which can lead to a highly-degenerate spin structure. Large moment systems, such as Ho${}_2$Ti${}_2$O${}_7$ and Dy${}_2$Ti${}_2$O${}_7$, tend to host a classical spin ice state with low-temperature spin freezing and emergent magnetic monopoles. Systems with smaller effective moments, such as Pr${}^{3+}$-based pyrochlores, have been proposed as excellent candidates for hosting a "quantum spin ice" characterized by entanglement and a slew of exotic quasiparticle excitations. However, experimental evidence for a quantum spin ice state has remained elusive. Here, we show that the low-temperature magnetic properties of Pr${}_2$Sn${}_2$O${}_7$ satisfy several important criteria for continued consideration as a quantum spin ice. We find that Pr${}_2$Sn${}_2$O${}_7$ exhibits a partially spin-frozen ground state with a large volume fraction of dynamic magnetism. Our comprehensive bulk characterization and neutron scattering measurements enable us to map out the magnetic field-temperature phase diagram, producing results consistent with expectations for a ferromagnetic Ising pyrochlore. We identify key hallmarks of spin ice physics, and show that the application of small magnetic fields ($\hat{I}{¼}_0{H}_c\sim$0.75T) suppresses the spin ice state and induces a long-range ordered magnetic structure. Together, our work clarifies the current state of Pr${}_2$Sn${}_2$O${}_7$ and encourages future studies aimed at exploring the potential for a quantum spin ice ground state in this system.