Dipolar spin ice regime proximate to an all-in-all-out Néel ground state in the dipolar-octupolar pyrochlore Ce_2Sn_2O_7

The dipolar-octupolar (DO) pyrochlores, R_2M_2O_7 (R = Ce, Sm, Nd), are key players in the search for realizable novel quantum spin liquid (QSL) states as a large parameter space within the DO pyrochlore phase diagram is theorized to host QSL states of both dipolar and octupolar nature. New single crystals and powders of Ce_2Sn_2O_7, synthesized by hydrothermal techniques, present an opportunity for a new characterization of the exchange parameters in Ce_2Sn_2O_7 using the near-neighbor XYZ model Hamiltonian associated with DO pyrochlores. Utilizing quantum numerical linked cluster expansion fits to heat capacity and magnetic susceptibility measurements, and classical Monte Carlo calculations to the diffuse neutron diffraction of the new hydrothermally grown Ce_2Sn_2O_7 samples, we place Ce_2Sn_2O_7's ground state within the ordered dipolar all-in-all-out (AIAO) Néel phase, with quantum Monte Carlo calculations showing a transition to long-range order at temperatures below those accessed experimentally. Indeed, our new neutron diffraction measurements on the hydrothermally grown Ce_2Sn_2O_7 powders show a broad signal at low scattering wave vectors, reminiscent of a dipolar spin ice, in striking contrast from previous powder neutron diffraction on samples grown from solid-state synthesis, which found diffuse scattering at high scattering wave vectors associated with magnetic octupoles and suggested an octupolar quantum spin ice state. We conclude that new hydrothermally grown Ce_2Sn_2O_7 samples host a finite-temperature proximate dipolar spin ice phase, above the expected transition to AIAO Néel order.