Hyperfine Interactions of Sc Impurities in Sapphire

G. N. DARRIBA; M. RENTERÍA

Canberra

Conferencia; 5th Joint International Conference on Hyperfine Interactions and Symposium on Nuclear Quadrupole Interactions (HFI/NQI 2014); 2014

In this work we present a theoretical study of structural, electronic, and hyperfine properties of alpha-Al2O3 semiconductor doped with Sc impurities using ab initio Density Functional Theory calculations. Recently, we have performed similar studies in alpha-Al2O3 using acceptor or donor impurities, such as Cd and Ta atoms, respectively [PRB 86, 075203(2012)]. These ab initio calculations were compared with Time-Differential γ-γ Perturbed Angular Correlation (PAC) experiments using (111In)111Cd and (181Hf)181Ta nuclides as PAC probes.  On the other hand, 44Sc can be used as a non-standard PAC probe using the (44Ti)44Sc decay. In this way, it is interesting to perform  a reliable structural, electronic, and hyperfine theoretical study  of Sc-doped alpha-Al2O3 that could be compared with results coming from  44Sc PAC experiments, now in progress. The ab initio calculations were performed with the Full-Potential Augmented Plane Wave plus Local Orbitals (FP-APW+lo) method using the Wien2K code. We studied different Sc concentrations in order to simulate the isolated impurity condition present in PAC experiments. Sc is an isovalent impurity when it replaces the Al atom, nevertheless we performed calculations for different charge states of the impurity. We demonstrate that no magnetic interaction is present at Sc site and therefore a pure quadrupole hyperfine interaction is predicted. The electronic structures and the electric-field gradient are also compared with those obtained for acceptor and donor impurities in alpha-Al2O3.