@article{10902/31490,
year = {2011},
month = {9},
url = {https://hdl.handle.net/10902/31490},
abstract = {The coordination, the electronic structures and the spin of the ground state of Ni(3+) (3d(7)) and Co(3+) (3d(6)) introduced as impurities in LaAlO(3) are investigated through optical spectroscopy and magnetic measurements. The unusual trivalent valence state in both transition-metal ions was stabilised via a sol-gel process followed by high oxygen pressure treatments. We show that the crystal-field strength at the nearly O(h) transition-metal site in LaAlO(3) locates Ni(3+) and Co(3+) near the spin state crossover, yielding a low-spin ground state in both cases. We analyse how the interplay between the Jahn-Teller (JT) effect and the spin state affects the magnetic moment of the ion and its temperature dependence. The optical spectra reveal a JT effect associated with a low-spin ground state in Ni(3+) and with a thermally populated high-spin low-lying first excited state in Co(3+). The corresponding JT distortions are derived from structural correlations. We conclude that the JT effect is unable to stabilise the intermediate spin state in Co(3+). A low-spin ground state in thermal equilibrium with a high-spin low-lying first excited state is detected in diluted Co(3+)-doped LaAlO(3). These results are compared with those obtained in the parent pure compounds LaNiO(3) and LaCoO(3).},
organization = {Financial support from the Spanish Ministerio de Ciencia e Innovacion (project no. MAT2008-06873-C02-01/MAT) is acknowledged. FR thanks the Research Intensification Programme (I3) of the University of Cantabria for partial support and MNS-O thanks the MEC for an FPU grant (ref. AP-2004-5954). This work has been carried out within the framework of the MALTA Consolider Ingenio 2010 program (ref. CSD2007-00045).},
publisher = {IOP Publishing},
publisher = {Journal of Physics Condensed Matter, 2011, 23(41), 415501},
title = {Optical and magnetic characterisation of Co3+ and Ni3+ in LaAlO3: interplay between the spin state and Jahn-Teller effect},
author = {Sanz Ortiz, Marta Norah and Rodríguez González, Fernando and Rodríguez Fernández, Jesús and Demazeau, Gérard},
}