The role of iron in the formation of the magnetic structure and related properties of La0.8Sr0.2Co1−xFexO3 (x=0.15, 0.2, 0.3)

• Published in: Journal of magnetism and magnetic materials Vol. 320; no. 5; pp. 651 - 661
• Main Authors: Klencsár, Z., Németh, Z., Kuzmann, E., Homonnay, Z., Vértes, A., Hakl, J., Vad, K., Mészáros, S., Simopoulos, A., Devlin, E., Kallias, G., Grenéche, J.M., Cziráki, Á., De, S.K.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Science 01.03.2008
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Magnetic properties and materials; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Mössbauer effect; other γ-ray spectroscopy; Physics; Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.); Negative magnetoresistance; Spin glasses; Moessbauer effect; Magnetization; Magnetic cluster; 76.60.Es Magnetoresistance; Magnetic relaxation; 75.50.Lk; Electron delocalization; Electronic density of states; Cluster glass; 76.80.+y; Magnetic susceptibility; Ferrites; Spin cluster; 73.43.Qt; Mössbauer-spectroscopy; High spin states; Spin crossover; Magnetic structure
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2007.08.002

La0.8Sr0.2Co1-xFexO3 (x=0.1,0.,0.3) samples were studied by means of AC magnetic susceptibility, magnetization, magnetoresistance and 57Fe Mossbauer spectrometry. Iron was found to take on a high spin 3d5-alpha electronic state in each of the samples, where alpha refers to a partly delocalized 3d electron. The compounds were found to exhibit a spin-cluster glass transition with a common transition temperature of 53K. The spin-cluster glass transition is visualized in the 57Fe Mossbauer spectra as the slowing down of magnetic relaxation below 70K, thereby showing that iron takes part in the formation of the glassy magnetic phase. The paramagnetic-like phase found at higher temperatures is identified below Tcapprox 195K as being composed of weakly interacting, magnetically ordered nanosized clusters of magnetic ions in part with a magnetic moment oriented opposite to the net magnetic moment of the cluster. For each of the samples a considerable low-temperature negative magnetoresistance was found, whose magnitude in the studied range decreases with increasing iron concentration. The observed results obtained on the present compounds are qualitatively explained assuming that the absolute strengths of magnetic exchange interactions are subject to the relation JCo-Co < JFe-Co < JFe-Fe.