Absence of moment fragmentation in the mixed \(B\)-site pyrochlore Nd\(_{2}\)GaSbO\(_{7}\)

Abstract

Nd-based pyrochlore oxides of the form Nd\(_{2}B_{2}\)O\(_{7}\) have garnered a significant amount of interest owing to the moment fragmentation physics observed in Nd\(_{2}\)Zr\(_{2}\)O\(_{7}\) and speculated in Nd\(_{2}\)Hf\(_{2}\)O\(_{7}\). Notably this phenomenon is not ubiquitous in this family, as it is absent in Nd\(_{2}\)Sn\(_{2}\)O\(_{7}\), 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 Nd\(_{2}\)GaSbO\(_{7}\). The \(B\)-site of this system is characterized by significant disorder and an extremely small average ionic radius. Similarly to Nd\(_{2}\)Sn\(_{2}\)O\(_{7}\), 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 Nd\(_{2}\)GaSbO\(_{7}\) 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.