resumo
The evolution of the crystal structure and the magnetic properties was investigated in the La0.5Sr0.5CoO3-delta (0 < delta < 0.3) system as a function of the oxygen deficit delta. Compounds with a low oxygen deficit (delta < 0.1) are shown to be predominantly ferromagnetic, while further increase (delta > 0.1) gradually changes the magnetic structure from ferromagnetic to G-type antiferromagnetic and causes a structural transition from rhombohedral to cubic symmetry. Resistivity and magnetoresistance at low temperature increase with increasing of oxygen vacancies. It is argued that oxygen reduction facilitates stabilization of the high spin state of Co3+ ions. Antiferromagnetic interactions between cobalt ions in the high spin state are found to dominate in compounds with the oxygen deficit delta > 0.18.
palavras-chave
CRYSTAL-STRUCTURE; SPIN-STATE; THIN-FILMS; MAGNETORESISTANCE; LA1-XSRXCOO3; LACOO3; FERROMAGNETISM; ORIGIN; ORDER
categoria
Physics
autores
Karpinsky, DV; Troyanchuk, IO; Lobanovsky, LS; Chobot, AN; Ritter, C; Efimov, V; Sikolenko, V; Kholkin, AL
nossos autores
Andrei Kholkin
Investigador Jubilado
Dzmitry Karpinski (Karpinsky)
Bolseiro de pós-Doutoramentoagradecimentos
This research project has been supported by BRFFI (grant F12R-057). One of the authors (DVK) acknowledges the financial support from the FCT (grant No. SFRH/BPD/42506/2007). The Center for Research in Ceramic and Composite Materials (CICECO) is acknowledged for partial support. Drs F Figueiras and S Das are acknowledged for the help with magnetization measurements.