Several physical properties of the superconducting Heusler compounds, focusing on two systems (Y, Lu, Sc)Pd 2 Sn and APd 2 M, where A=Hf, Zr and M=Al, In, are summarized and compared. The analysis of the data shows the importance of the electron-phonon coupling for superconductivity in this family. We report the superconducting parameters of YPd 2 Sn, which has the highest T c among all known Heusler superconductors.

Antiferromagnetic order in MnO spherical nanoparticlesWe have performed unpolarized and polarized neutron diffraction experiments on monodisperse 8-and 13-nm antiferromagnetic MnO nanoparticles. For the 8-nm sample, the antiferromagnetic transition temperature T N (114 K) is suppressed compared to that in the bulk material (119 K), while for the 13-nm sample T N (120 K) is comparable to that in the bulk. The neutron diffraction data of the nanoparticles is well described using the bulk MnO magnetic structure but with a substantially reduced average magnetic moment of 4.2 ± 0.3 μ B /Mn for the 8-nm sample and 3.9 ± 0.2 μ B /Mn for the 13-nm sample. An analysis of the polarized neutron data on both samples shows that in an individual MnO nanoparticle about 80% of Mn ions order. These results can be explained by a structure in which the monodisperse nanoparticles studied here have a core that behaves similar to the bulk with a surface layer which does not contribute significantly to the magnetic order.

Magnetic susceptibility results for single crystals of the new cubic compounds UT2Al20 (T=Mn, V, and Mo) are reported. Magnetization, specific heat, resistivity, and neutron diffraction results for a single crystal and neutron diffraction and inelastic spectra for a powder sample are reported for UMn2Al20. For T = V and Mo, temperature independent Pauli paramagnetism is observed. For UMn2Al20, a ferromagnetic transition is observed in the magnetic susceptibility at Tc = 20 K. The specific heat anomaly at Tc is very weak while no anomaly in the resistivity is seen at Tc. We discuss two possible origins for this behavior of UMn2Al20: moderately small moment itinerant ferromagnetism, or induced local moment ferromagnetism.