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The anomalous behavior of the heavy-fermion superconductor UBe13, which appears below the superconducting transition temperature Tc ~ 0.9 K, has been investigated by point-contact spectroscopy and the Josephson effect. An abrupt increase in the temperature dependence of the Josephson critical current is observed below 0.7K between UBe13 and conventional superconductors. The zero-bias resistance of the point contacts between UBe13 and Pt decreases continuously below Tc and shows an abrupt drop at 0.5-0.6 K. These results suggest that the anomaly originates from superconductivity rather than magnetism, which has been considered as one of the origins of the anomaly. [ABSTRACT FROM AUTHOR]

A novel star-shaped high-spin Fe(III) tetranuclear cluster was unexpectedly obtained by the reaction of an [FeIII(phsal)2]- anion with an Fe(II) coordination cation (H2phsal: N-(2-hydroxyphenyl)salicylaldimine). Despite a star-shaped Fe(III) tetranuclear structure similar to reported Fe(III) single molecule magnets, the present compound exhibited a bulk antiferromagnetic transition at 0.6K due to a magnetic exchange coupling through intercluster π-stacking interactions. [ABSTRACT FROM AUTHOR]

The magnetization change ΔM at the superconducting transition of LaIrSi3 has been measured in various magnetic fields H. The observed ΔM in H = 0 is within the range of the Meissner effect induced by the possible residual field, suggesting that the spontaneous magnetization, if it exists, is below the experimental accuracy. This result is in agreement with the results of μSR experiments, in which no spontaneous magnetic field has been observed in the superconducting state. [ABSTRACT FROM AUTHOR]

The Josephson effect between a single-crystal UPt3 and a conventional superconductor Al has been investigated under pressure for the junction on the UPt3 surface perpendicular to the hexagonal c[0001] axis. Simultaneously measured magnetization has revealed that the Meissner fraction approaches a minimum value of ~1% at the critical pressure of Pc~0.4 GPa. The critical temperature Tc and the temperature TJ where a measurable Josephson critical current Ic first appears decrease with increasing pressure; the decreasing rate of |dTc/dP| is almost constant, whereas |dTJ/dP| shows an abrupt increase above Pc, indicating that the Josephson effect is suppressed above Pc. These results, together with the decrease in penetration depth λ derived from the magnetic-field dependence of Ic, suggest that the superconducting phase is modified above Pc by the disappearance of the symmetry-breaking antiferromagnetic order. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Among many two-dimensional (2D) high Tc superconductors, graphite intercalation compounds (GICs) are the most famous intercalation family, which are classified as typical electron-phonon mediated superconductors. We show unambiguous experimental facts that BaC6, the superconductivity of which has been missing for many years sofar among various alkaline earth metal (Ca, Sr, and Ba) intercalted GICs, exhibits superconductivity at Tc = 65 mK. By adding this finding as the additional experimental point, a complete figure displaying the relationship between Tc and interlayer distance (d) for GICs is now provided, and their possible superconducting mechanisms raised sofar are revisited. The present study settles a long-running debate between theories and experiments on the superconductivity in the first stage GICs. [ABSTRACT FROM AUTHOR]

We have performed parallel measurements of dc-magnetization and ac-magnetic susceptibility for a ferromagnetic superconductor, UGe2 , in the ferromagnetic-superconducting phase. dc-magnetization measurements revealed that adequate demagnetizing of the sample allows for the preparation of various magnetized states with different zero-field residual magnetization. We observed that these states exhibit varying ac superconducting response at large ac-field amplitudes. The amount of ac flux penetration is less in the demagnetized state involving many domain walls. This result seems to contradict the theory that considers the domain walls as weak links. Moreover, the ferromagnetic domain walls enforce the shielding capability of superconductivity. This observation sheds light on the role of the domain walls on superconductivity, which has been a controversial issue for several decades. Two possible scenarios are presented to explain the enhancement of the shielding capability by the domain walls. [ABSTRACT FROM AUTHOR]