Magnetic properties around quantum critical point of CePt1-xRhx

In order to investigate magnetic properties around a quantum critical point of CePt1-xRhx alloys, we have performed the ac-susceptibility (χac) measurements with field frequency ranging from ω/2π=0 (dc magnetization) to 1113 Hz for temperature down to 100 mK on polycrystalline CePt1-xRhx (x=0.5, 0.6). The in-phase component of χac exhibits a pronounced peak at Tf. The peak magnitude and Tf show significant field-frequency dependence. In addition, a staircaselike hysteresis loop of magnetization was observed below 200 mK. From the dynamical analyses of χac, we suggest that CePt0.5Rh0.5 and CePt0.4Rh0.6 can be described as cluster-glass systems.