On the incorporation of nickel into hexagonal barium titanate: magnetic properties and electron paramagnetic resonance (EPR)

Systematic measurements of the magnetic moment of hexagonal 6H-BaTiO3- 0.04 BaO ? x NiO (0.005 <= x <= 0.02) ceramics were performed to study the influence of Ni ions on the magnetic properties. By temperature-dependent measurements of the paramagnetic susceptibility at 90 kOe, the Ni2+ ion was identified as the majority defect in air-sintered Ni-doped hexagonal barium titanate. Q-band EPR investigations of a 2.0 mol% Ni-doped single crystal revealed three different Ni centers located at Ti sites: first, Ni3+ ions at Ti sites in intact oxygen octahedra, second, Ni3+ associated with an oxygen vacancy and third, the presence of Ni2+ centers leading to a forbidden transition. The Ni3+-VO associate characterized by a vacancy in the face-sharing oxygen plane of the oxygen octahedra can be ruled out. The crystal field parameters of the Ni(2+)defect were estimated by a combined fitting of the paramagnetic susceptibility and the EPR fine structure parameter D to B-0(4) approximate to -17,300 cm(-1), vertical bar B-0(2)vertical bar approximate to 2500 cm(-1) and B-3(4) approximate to 19,000 cm(-1).

Automated summary

Systematic measurements were performed on Ni-doped hexagonal 6H-BaTiO3 ceramics to study the magnetic properties, with Ni2+ ions identified as the main defects and Ni3+ associated with Ti sites and oxygen vacancies.