Magnetic ordering in the pressure-stabilized high-temperature phase ofYbInCu4

Abstract

To elucidate the ground state of the pressure-stabilized high-temperature (HT) phase of ${\mathrm{YbInCu}}_{4},$ we have carried out electrical resistivity $\ensuremath{\rho}$ and ac-susceptibility ${\ensuremath{\chi}}_{\mathrm{ac}}$ measurements at high pressures. For pressures above 2.49 GPa, the first-order valence transition is completely suppressed (below $\ensuremath{\sim}80\mathrm{mK}).$ Separately, above 2.39 GPa, a clear peak appears in ${\ensuremath{\chi}}_{\mathrm{ac}}$ with a small kink in $\ensuremath{\rho}$ at around ${T}_{M}=2.4\mathrm{K}.$ The ${\ensuremath{\chi}}_{\mathrm{ac}}$ peak is easily diminished by applying low magnetic fields and disappears above $\ensuremath{\sim}500\mathrm{Oe}.$ The characteristic behavior of ${\ensuremath{\chi}}_{\mathrm{ac}}$ at ${T}_{M}$ can generally be ascribed to the onset of long-range ferromagnetic ordering and, therefore, the ground state of the pressure-stabilized HT phase is most probably a ferromagnetically ordered state. This result is compatible with the occurrence of weak ferromagnetism recently reported for the Y-substituted compound ${\mathrm{Yb}}_{0.8}{\mathrm{Y}}_{0.2}{\mathrm{InCu}}_{4}$ under pressure of 1.2 GPa.