In:
Journal of Applied Physics, AIP Publishing, Vol. 79, No. 8 ( 1996-04-15), p. 5428-5430
Kurzfassung:
Ni–Co ferrite has been studied with Mössbauer spectroscopy and x-ray diffraction. The crystal structure for this system is spinel, and the lattice constant is in accord with Vegard’s law. The Mössbauer spectra consist of two six-line patterns corresponding to Fe3+ at the tetrahedral (A) and octahedral (B) sites. The Néel temperature increases linearly with Ni concentration, suggesting the superexchange interacion for the Ni–O–Fe link is stronger than that for the Co–O–Fe link. It is found that Debye temperatures for the A and B sites of CoFe2O4 and NiFe2O4 are found to be θA=734 K, θB=248 K, and θA=378 K, θB=357 K, respectively. The intensity ratio of the A to B patterns is found to increase at low temperatures with increasing temperature due to the large difference of Debye temperatures of the two sites and to decrease at high temperatures due to migration of Fe3+ ions from A to B sites. Atomic migration of CoFe2O4 starts near 400 K and increases rapidly with increasing temperature to such a degree that 69% of the ferric ions as the A sites have moved over to the B sites by 780 K. It is noted that, as the Ni concentration in cobalt ferrite increases, the Debye temperatures tend to decrease the migration at the A and B sites is slow.
Materialart:
Online-Ressource
ISSN:
0021-8979
,
1089-7550
Sprache:
Englisch
Verlag:
AIP Publishing
Publikationsdatum:
1996
ZDB Id:
220641-9
ZDB Id:
3112-4
ZDB Id:
1476463-5
