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Abstract:
Below the hidden order transition temperature View the MathML sourceT0∼17K, ambient pressure 29Si and 99Ru NMR spectra in an aligned powder of URu2Si2 reveal local internal field distributions at both 29Si and 99Ru sites. For a longitudinal field orientation, the 99Ru spectral parameters also reveal a second transition temperature View the MathML sourceT*∼12K, below which an anomalous increase in the linewidth is observed, accompanied by a kink in the Knight shift vs. magnetic susceptibility plot. From temperature and applied-field orientation studies, we can separate the two types of linewidth contributions, and find that the distribution of internal fields arising below T0T0 is anisotropic at 99Ru positions, with larger widths in the ab -plane. The second contribution to the linewidth appears below T*T* and has Ising symmetry. We discuss disorder in the non-magnetic sector as a way to understand our measurements and reconcile them with recent pressure experiments by other groups.
