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 CeIn3 exhibits a field-induced anomaly associated with Fermi surface reconstruction at H∗∼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 In115 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∗.