Absence of moment fragmentation in the mixed B-site pyrochlore Nd2GaSbO7

Nd-based pyrochlore oxides of the form Nd2B2O7 have garnered a significant amount of interest owing to the moment fragmentation physics observed in Nd2Zr2O7 and speculated in Nd2Hf2O7. Notably this phenomenon is not ubiquitous in this family, as it is absent in Nd2Sn2O7, which features a smaller ionic radius on the B site. Here, we explore the necessary conditions for moment fragmentation in the Nd pyrochlore family through a detailed study of the mixed B-site pyrochlore Nd2GaSbO7. The B site of this system is characterized by significant disorder and an extremely small average ionic radius. Similarly to Nd2Sn2O7, we find no evidence for moment fragmentation through our bulk characterization and neutron scattering experiments, indicating that chemical pressure (and not necessarily the B-site disorder) plays a key role in the presence or absence of this phenomenon in this material family. Surprisingly, the presence of significant B-site disorder in Nd2GaSbO7 does not generate a spin-glass ground state and instead the same all-in-all-out magnetic order identified in other Nd pyrochlores is found here.