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EPR and optical properties of PbMoO4:Co single crystals
|Slawomir M. Kaczmarek 1, Taiju Tsuboi 3, Yoshio Nakai 3, Marek Berkowski 2, Tomasz Skibiński 1, Grzegorz Leniec 1, Zbigniew Kowalski 1|
1. West Pomeranian University of Technology, Szczecin (ZUT), Szczecin 70-310, Poland
PbMoO4:Co (0.2 mol. %, 0.5 mol.% and 1 mol.%) single crystals have been prepared by Czochralski method. They were investigated by electron paramagnetic resonance (EPR)and photoluminescence (PL) in a wide temperature range of 3-300 K. EPR investigations of oriented single crystal samples show clear signals with hyperfine structure due to Co2+ ions with a spin S=3/2, vanishing over 35 K. Temperature dependence of double integral of EPR signal obeys the Curie-Weiss law. Some discrepancies, however, are observed above5 K, suggesting the presence of internal magnetic fields due to e.g. clusters. It reveals low ferromagnetic interactions with Curie-Weiss temperature estimated as 1.8 and 2.8 K at 0.2 and 0.5 mol % Co up to 10K, respectively. Above 10K the magnetic phase changes to antiferromagnetic phasewith Curie-Weiss temperature of about -12 K.
The PL spectra show a broad band in a range from 400 to 700 nm.
We observed blue PL emission due to electronic transitions within the isolated [MoO4] tetrahedron groups and green emission due to extrinsic transitions caused by the defects or impurities. Temperature dependence of PL spectrum shows ananomaly in a range of 100-200 K, indicating a structural phase transition at about 175 K.
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Presentation: Poster at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, Topical Session 6, by Slawomir M. Kaczmarek
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17
Submitted: 2013-03-23 14:55 Revised: 2013-05-06 13:50