# Intermultiplet transitions and magnetic long-range order in Sm-based pyrochlores

## TL;DR

This study investigates the magnetic properties of Sm-based pyrochlores using neutron scattering and heat capacity measurements, revealing the importance of intermultiplet transitions and identifying long-range magnetic order in these materials.

## Contribution

It provides a detailed analysis of the crystalline electric field levels and demonstrates the significance of intermultiplet transitions in understanding the magnetic behavior of Sm pyrochlores.

## Key findings

- Heat capacity anomalies at 350 mK and 440 mK indicate magnetic phase transitions.
- Intermultiplet transitions are crucial for accurate CEF modeling of Sm ions.
- Long-range all-in-all-out order in stannate; dipolar order inferred in titanate.

## Abstract

We present bulk and neutron scattering measurements performed on the isotopically enriched $^{154}\mathrm{Sm_2Ti_2O_7}$ and $^{154}\mathrm{Sm_2Sn_2O_7}$ samples. Both compounds display sharp heat capacity anomalies, at 350 mK and 440 mK, respectively. Inelastic neutron scattering measurements are employed to determine the crystalline electric field (CEF) level scheme, which includes transitions between the ground-state and first excited $J$ multiplets of the $\mathrm{Sm}^{3+}$ ion. To further validate those results, the single-ion magnetic susceptibility of the compounds is calculated and compared with the experimental DC-susceptibility measured in low applied magnetic fields. It is demonstrated that the inclusion of intermultiplet transitions in the CEF analysis is fundamental to the understanding of the intermediate and, more importantly, low temperature magnetic behaviour of the Sm-based pyrochlores. Finally, the heat capacity anomaly is shown to correspond to the onset of an all-in-all-out long-range order in the stannate sample, while in the titanate a dipolar long-range order can be only indirectly inferred.