Ba 8 Cu x Ge 46 x is a type-I clathrate material that forms as a semiconductor in a narrow composition range corresponding to the electron-balanced Zintl composition, with x = 5.3. We use NMR spectroscopy combined with ab-initio electronic structure calculations to probe the electronic and structural behavior of these materials. Computational results based on a superstructure model for the atomic configuration of the alloy provide good agreement with the electric quadrupole-broadened NMR lineshapes. Modeling using the modified Becke-Johnson (TB-mBJ) exchange potential is also shown to agree well with experimental NMR Knight shifts. The results indicate that the Cu-Ge balance is the main factor determining the carrier density, within a narrow stability range near the ideal Zintl composition. Cite as: J. Alloys Compd. 593, 261 (2014), published version © 2014 Elsevier B.V. link to published version: http://dx.

We report the direct observation of an electrically-induced magnetic susceptibility in the molecular nano- magnet [Fe3O(O2CPh)6(py)3]ClO4·py, an Fe3 trimer. This magnetoelectric effect results from the breaking of spatial inversion symmetry due to the spin configurations of the antiferromagnetic trimer. Both static and very low frequency electric fields were used. Fractional changes of the magnetic susceptibility of 11 ppb$$\pm 2$$ ± 2 per kVm-1 for the temperature range 8.5 < T < 13.5 K were observed for applied electric fields up to 62 kV m−1. The changes in susceptibility were measured using a tunnel diode oscillator operating at liquid helium temperatures while the sample is held at a higher regulated temperature.