J. Phys. IV France 07 (1997) C1-267-C1-268
Magnetic Phase Diagram for the Spinel Ferrite Series MgFe2-xCrxO4 and Mg1-xZnxFel.5Cr0.5O4 as Determined by Mössbauer SpectroscopyP.M.A. de Bakker1, R.E. Vandenberghe2 and E. de Grave2
1 SCKCEN, Boeretang 200, 2400 Mol, Belgium
2 Department of Subatomic and Radiation Physics, University of Gent, Proeftuinstraat 86, 9000 Gent, Belgium
The spinel series MgFe2-xCrxO4 (0.0≤x≤2.0) (MFC) and Mg1-xZnxFel.5Cr0.5O4 (0.0≤x≤1.0) (MZFC) are progressively diluted on the A-sites by non-magnetic Mg2+ and/or Zn2+ ions as x increases. The different magnetic states as a function of temperature and composition could be determined by Mössbauer spectroscopy in conjunction with high external magnetic fields. From the spectra it was derived that only for the spinel samples MFC with x≤0.6 and MZFC with ≤0.1 a pure ferrimagnetic behavior exists down to 4K. In the composition range 0.8≤x≤1.2 for MFC and 0.2≤x≤0.7 for MZFC a marked canting of the A- and B-site spins was observed below a characteristic temperature Tf indicating a re-entrant semi-spinglass behavior. Finally, for the samples with x>1.2 (ZFC) and x>0.7 (MZFC) an incomplete alignment of the spins remained up to the paramagnetic transition temperature Tg pointing to pure semi-spin glasses. Together with the temperature dependence of the average magnetic hyperfine field the complete magnetic phase diagram could be derived.
© EDP Sciences 1997