Peculiar superconductivity in PrOs4Sb12 probed by local magnetization

We performed local magnetization measurements in the superconducting state of PrOs4Sb12 using micro-Hall probe. For a magnetic field applied along one of the principal axes, a remarkable dip structure in the magnetization hysteresis loop was observed close to zero local magnetic induction. The anomaly is most pronounced when the magnetic field is applied only in a certain axis of the crystal, and is not observed along other two axes. We believe that the anomaly close to zero induction is universal to the spin-triplet superconductors with broken time-reversal symmetry.