27Al NMR/NQR Studies of YbAl3C3

Abstract

The phase transition at T * = 80 K in YbAl 3 C 3 has been studied by 27 Al nuclear quadrupole resonance (NQR) measurement and nuclear magnetic resonance (NMR) measurement up to 30 T. The NQR and NMR spectra reveal clear anomalies just below T * , which provides the first microscopic evidence for symmetry lowering in the low-temperature phase below T * . The transition is characterized by marked changes in the 27 Al-NQR frequencies ν Q 's without significant changes in the lattice parameters. The field dependence of the transition is also investigated. The NMR line exhibits field-induced rapid broadening below T * , which almost vanishes in zero field. Moreover, we found that T * increases by 10 K at 30 T. These unique magnetic properties are consistent with the scheme that the microscopic mechanism underlying the phase transition involves Yb-4 f electrons rather than the scheme of a simple structural phase transition.