SANZ-ORTIZ, Marta N.; RODRÍGUEZ, Fernando; RODRÍGUEZ, Jesús; DEMAZEAU, Gérard

doi:10.1088/0953-8984/23/41/415501

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SANZ-ORTIZ, Marta N.
MALTA Consolider Team, Facultad de Ciencias

RODRÍGUEZ, Fernando
MALTA Consolider Team, Facultad de Ciencias

RODRÍGUEZ, Jesús
MALTA Consolider Team, Facultad de Ciencias

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Journal of Physics: Condensed Matter. 2011, vol. 23, n° 41, p. 415501 (6 p.)

IOP Publishing

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The coordination, the electronic structures and the spin of the ground state of Ni3+ (3d7) and Co3+ (3d6) introduced as impurities in LaAlO3 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 Oh transition-metal site in LaAlO3 locates Ni3+ and Co3+ 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 Ni3+ and with a thermally populated high-spin low-lying first excited state in Co3+. The corresponding JT distortions are derived from structural correlations. We conclude that the JT effect is unable to stabilise the intermediate spin state in Co3+. A low-spin ground state in thermal equilibrium with a high-spin low-lying first excited state is detected in diluted Co3+-doped LaAlO3. These results are compared with those obtained in the parent pure compounds LaNiO3 and LaCoO3.< Réduire

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Inorganic compounds

Jahn-Teller effect

Crystal impurities

Spin

Lanthanum

Oxides

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Optical and magnetic characterisation of Co<sup>3+</sup> and Ni<sup>3+</sup> in LaAlO<sub>3</sub>: interplay between the spin state and Jahn-Teller effect

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