In order to study the crystal structure, phase relationships, and magnetic properties of the system Tb 5−x La x Si 2 Ge 2 , a series of polycrystalline samples with compositions ranging from x = 0 to x = 5 have been synthesized and characterized in detail. At room temperature, two structures have been detected: Compounds in the concentration range 0 x < 1 present a monoclinic Gd 5 Si 2 Ge 2 -type structure, while for x > 1 a tetragonal Zr 5 Si 4 -type structure is observed. The unit cell volume increases linearly with La concentration but with two different slopes: ∼18Å3 /x and ∼33Å 3 /x for 0 x < 1 (monoclinic) and x > 1 (tetragonal), respectively. In the monoclinic region, an increase of T C was observed, reaching a maximum value of T C ∼ 154 K, at the x = 0.75 composition. This feature is explained based on specific La occupancy at the R2 site which was supported by density functional calculations for low La concentration. The samples that crystallized in the tetragonal structure exhibit a linear decrease of T C (x) with a slope of ∂T C /∂x ∼ −38 K/x, reaching 0 K for the x = 5 composition. A magnetic and structural x-T phase diagram of the Tb 5−x La x Si 2 Ge 2 system in the temperature range 4-300 K is proposed.

The hyperfine interaction between the quadrupole moment of atomic nuclei and the electric field gradient (EFG) provides information on the electronic charge distribution close to a given atomic site. In ferroelectric materials, the loss of inversion symmetry of the electronic charge distribution is necessary for the appearance of the electric polarization. We present first-principles density functional theory calculations of ferroelectrics such as BaTiO3, KNbO3, PbTiO3 and other oxides with perovskite structures, by focusing on both EFG tensors and polarization. We analyze the EFG tensor properties such as orientation and correlation between components and their relation with electric polarization. This work supports previous studies of ferroelectric materials where a relation between EFG tensors and polarization was observed, which may be exploited to study the ferroelectric order when standard techniques to measure polarization are not easily applied.

The versatility of perturbed angular correlations (PAC) in the study of nanostructures and thin films is demonstrated, namely for the specific cases of ZnO/CdxZn1−xO thin films and Ga2O3 powder pellets and nanowires, examples of transparent conductive oxides. PAC measurements as a function of annealing temperature were performed after implantation of 111mCd/111Cd (T1/2 = 48 min) and later compared to density functional theory simulations. For ZnO, the substitution of Cd probes at Zn sites was observed, as well as the formation of a probe‐defect complex. The ternary CdxZn1−xO (x = 0.16) showed good macroscopic crystal quality but revealed some clustering of local defects around the probe Cd atoms, which could not be annealed. In the Ga2O3 samples, the substitution of the Cd probes in the octahedral Ga‐site was observed, demonstrating the potential of ion‐implantation for the doping of nanowires.

Ga 2 O 3 bulk single crystals have been implanted with 300 keV Europium ions to fluences ranging from 1×10 13 to 4×10 15 at/cm 2 . The damage build-up and Eu-incorporation was assessed by Rutherford Backscattering Spectrometry in the channeling mode (RBS/C). RBS/C results suggest that implantation causes a mixture of defect clusters and extended defects such as dislocations. Amorphisation starts at the surface for fluences around 1×10 15 at/cm 2 and then proceeds to deeper regions of the sample with increasing fluence. Amorphous regions and defect clusters are efficiently removed during rapid thermal annealing at ~1100 ºC; however, Eu diffuses towards the surface. Nevertheless, Eu ions are optically activated and show cathodoluminescence at room temperature. Results in bulk samples are compared to those in Eu-implanted Ga 2 O 3 nanowires and despite strong similarities in the structural properties differences were found in the optical activation. Furthermore, damage and dopant incorporation studies were performed using the Perturbed Angular Correlation technique, which allows probing the immediate lattice surroundings of an implanted radioactive probe at the atomic level.

We report the synthesis, crystal structures, thermal, optical and magnetic properties of three new metal dicyanamide frameworks comprising benzyltrimethylammonium cations (BeTriMe+) as labile guests. These compounds crystallize in as two-dimensional...