High-field phase diagram of the heavy-fermion metal CeIn3: Pulsed-field NMR study on single crystals up to 56 T

The heavy-fermion antiferromagnet ${\mathrm{CeIn}}_{3}$ exhibits a field-induced anomaly associated with Fermi surface reconstruction at ${H}^{*}\ensuremath{\sim}45$ T, well below the antiferromagnetic (AFM) critical field that exceeds 60 T. In order to explore the origin of this anomaly, we have measured $^{115}\mathrm{In}$ NMR spectra in pulsed magnetic fields up to 56 T using high-quality single crystals. To within experimental resolution, we do not detect any change in the NMR spectra that could suggest a modification in either the character of the hyperfine field or the electric field gradient at In sites through ${H}^{*}$. This strongly suggests that the 45 T anomaly cannot be simply ascribed to a field-induced change in the magnetic structure of the AFM state. Neither do we find any evidence of changes in the crystallographic structure or in the distribution of charge density at ${H}^{*}$. The field dependence of the NMR shift implies the existence of a field-induced anomaly in the hyperfine coupling above ${H}^{*}$.