The LaAlO3/SrTiO3 interface provides an intriguing 2-dimensional electron system in which the coexistence of superconductivity and magnetism has been observed. This chapter presents preliminary results of ongoing angular dependent torque magnetometry measurements on SrTiO3-LaAlO3 heterostructures at different magnetic fields and temperatures. The authors have calculated the lattice thermal conductivity in layered oxide thermoelectric (TE) materials using perturbed molecular dynamics methods and tried to reveal the mechanisms of thermal conduction, thereby building up a strategy to control it. In order to achieve the next generation of nanometer sized electronic devices a detailed understanding and control of electrical transport is essential. The chapter reports on electronic transport measurements of biphenylpropanethiol (BP3) capped gold nanoparticles (AuNPs) with a diameter of 4 nm used as functional units. Controlled Vocabulary Terms electronic structure; lattice dynamics; magnetic fields; superconductivity

Using time-differential perturbed angular correlation spectroscopy we have measured the electric field gradient (EFG) at (111)Cd probe nuclei in solid Ce in a pressure range up to 8 GPa. Covering various allotropic phases of Ce, we find that the value of the EFG in the cubic alpha phase is almost four times larger than in the cubic gamma phase and close to values in the noncubic phases alpha' and alpha ''. These results together with the differences in time modulation of the spectra are interpreted as evidence for quadrupolar electronic charge-density ordering and symmetry lowering at the gamma ->alpha transition while the lattice remains face-centered cubic.

Using time-differential perturbed angular correlation spectroscopy we have measured the electric field gradient (EFG) at $^{111}\text{C}\text{d}$ probe nuclei in solid Ce in a pressure range up to 8 GPa. Covering various allotropic phases of Ce, we find that the value of the EFG in the cubic $\ensuremath{\alpha}$ phase is almost four times larger than in the cubic $\ensuremath{\gamma}$ phase and close to values in the noncubic phases ${\ensuremath{\alpha}}^{\ensuremath{'}}$ and ${\ensuremath{\alpha}}^{\ensuremath{''}}$. These results together with the differences in time modulation of the spectra are interpreted as evidence for quadrupolar electronic charge-density ordering and symmetry lowering at the $\ensuremath{\gamma}\ensuremath{\rightarrow}\ensuremath{\alpha}$ transition while the lattice remains face-centered cubic.

We use the time-differential perturbed angular correlation technique to study nuclear electric quadupole hyperfine interactions of probe 111Cd nuclei in cerium lattice sites at room temperature under pressures up to 8 GPa. We have found that the well known γ → α phase transition in cerium is not isostructural. In α-Ce, the probe 111Cd nuclei reveal a quadrupole electron charge density component that is absent in γ-Ce. The hidden spacial structure of electronic quadrupoles in α-Ce is triple-q antiferroquadrupolar, as was suggested in [14]. We relate our findings to the current understanding of the γ → α phase transition and also report on nuclear quadrupole interactions in other high-pressure phases of cerium: α″ (C2/m space symmetry) and α′ (α-U structure).

Using a small amount of radioactive 111Cd atoms implanted in cerium lattice to probe the hyperfine electric quadrupole interaction, we have detected a quadrupole electron charge density component in alpha-Ce, which is absent in gamma-Ce. The appearance of the quadrupole density in alpha-Ce predicted by the quadrupole scenario of the phase transition demonstrates that the spacial symmetry is lowered at the gamma->alpha phase transition. This finding makes cerium the first element where the symmetry change is driven exclusively by the valence electron degrees of freedom while the atomic centers of mass (cerium nuclei) occupy the face centered cubic positions. We also report on nuclear quadrupole interactions in other high pressure phases of cerium: alpha' (C2/m space symmetry) and alpha' (alpha-U structure).

The parameters of nuclear quadrupole hyperfine interaction in intermetallic UGe 2 and UAl 2 compounds have been measured in a temperature range of 100–300 K using the perturbed angular γγ correlation method on 111 Cd probe nuclei. The results obtained for UGe 2 indicate a pronounced anisotropic character in the distribution of f electrons in agreement with the calculation of the electronic structure of this compound. The hybridization degree between f electrons of U and p electrons of Al in UAl 2 is lower than the hybridization degree between f electrons of U and p electrons of Ge in UGe 2 .

The time-differential perturbed angular correlations technique (TDPAC) has been employed for measuring the parameters of hyperfine interactions in earlier known RAl3 compounds, synthesized at high pressure (8 GPa) and high temperature, where R = La, Ce, Sm, Gd, Th, Dy, Ho, Er, Yb and Lu. The Cd-111(In-111) radioactive atom was used as a probe nucleus. The X-ray method has revealed that with the increase in the atomic number of a rare-earth element R, the obtained RA13 high-pressure phases crystallize, respectively, into orthorhombic, hexagonal and cubic structures. It has been found that in the compounds containing R = La, Ce, Sm and Gd, a deviation from earlier known structural types and the formation of new ones is observed, which is associated with the change of the stoichiometric composition of the said compounds. The results of the PAC measurements have confirmed the deviation from the predetermined stoichiometric composition 1R:3Al for the compounds LaAl3, CeAl3, SmAl3 and GdAl3 and have verified the RAl3 stoichiometric structure for the other high-pressure phases obtained in this work. (c) 2007 Elsevier Ltd. All rights reserved.

The quadrupole interaction at 111Cd impurity nuclei in the intermediate-valence compound YbAl2 has been measured under pressure up to 80 kbar by the TDPAC spectroscopy. It was found that the quadrupole frequency nQ measured on the 111Cd located at the Al sites in YbAl2, varies nonlinearly and increases by almost four times with the pressure increase up to 80 kbar. A linear correlation between the mean Yb valence, derived from Yb L3 OFY-XAS and RXES measurements, and the electric field gradient (the quadrupole frequency nQ=eQVzz/h) has been observed. The quadrupole frequencies on 111Cd in the GdAl2, YbAl3, TmAl3 and CaAl2 compounds have been measured, also. The possibility of determining the valence of Yb in the Yb compounds with p-metals from the relation nQ (u(P)) = n2 + (n3 - n2) u(P) has been considered.

The quadrupole interaction at Cd-111 impurity nuclei in the intermediate-valence compound YbAl2 has been measured under pressure up to 80 kbar by the time-differential perturbed angular correlation spectroscopy. It was found that the quadrupole frequency nu(Q) measured on the Cd-111 nuclei located at the Al sites in YbAl2 varies nonlinearly and increases by almost four times with the pressure increase up to 80 kbar. A linear correlation between the mean Yb valence, derived from Yb L-3 OFY-XAS and RXES measurements, and the electric field gradient (the quadrupole frequency nu(Q)=eQV(zz)/h) has been observed. The quadrupole frequencies on Cd-111 in the GdAl2, YbAl3, TmAl3, and CaAl2 compounds have been also measured. The possibility of determining the valence of Yb in the Yb compounds with p metals from the relation nu(Q)(upsilon(P))=nu(2)+(nu(3)-nu(2))upsilon(P) has been considered.