Unconventional T - H Phase Diagram in the Noncentrosymmetric Compound Yb2Fe12P7

The temperature-(T-)magnetic-field (H) phase diagram for the noncentrosymmetric compound YbFeP, determined from electrical resistivity (rho), specific heat (C), and magnetization (M) measurements on single crystal specimens, is reported. This system exhibits a crossover from a magnetically ordered non-Fermi-liquid (NFL) phase at low H to another NFL phase at higher H. The crossover occurs near the value of H where the magnetic ordering temperature (T-M) is no longer observable in C(T, H)/T and rho(T, H), but not where T-M extrapolates smoothly to T = 0 K at a possible quantum critical point (QCP). This indicates the occurrence of a quantum phase transition between the two NFL phases. The lack of a clear relationship between the extrapolated QCP and NFL behavior suggests an unconventional route to the NFL ground states.