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We report magnetization of a non-centrosymmetric superconductor, LaPt3Si below 0.6 K up to 200 Oe. The home-made SQUID and Hall sensor magnetometers that operate below 1 K were constructed for this purpose. Although the SQUID magnetometer is more sensitive than the Hall sensor’s one, it was found not to work correctly for the rapid magnetization change of LaPt3Si below 0.4 K. The Hall sensor magnetometer, in contrast, can properly detect magnetization jumps in the M–H curve of the superconducting state. The observed flux jumps are probably related to the interfusion of the mixed state of the LaPt3Si that is observed in the μSR measurements.

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We have measured the magnetization of two unconventional superconductors: Sr 2 RuO 4 and LaNiC 2 using a SQUID magnetometer, both of which are reported to break time-reversal symmetry by µSR measurements. Even in the lowest residual magnetic field (< 10 −3 G), both show a magnetization of the order of 10 −5 G along the c-axis below the superconducting transition temperature. For Sr 2 RuO 4 , the magnitude of magnetization changes by applying a magnetic field of the order of the residual field, while LaNiC 2 does not show a remarkable change, suggesting that the former magnetization originates in the Meissner effect caused by the residual field. The spontaneous magnetization of LaNiC 2 , on the other hand, changes sign by mounting the crystal in the opposite direction along the c-axis and does not appear along the a-axis, indicating that it is closely related to the crystal structure lacking inversion symmetry along the c-axis.