Investigation of Ga substitution in cobalt ferrite ( Co Ga x Fe 2 − x O 4 ) using Mossbauer spectroscopy

• Published in: Journal of applied physics 2008-04, Vol.103 (7), p.07E508-07E508-3
• Main Authors: Krieble, K., Devlin, M., Lee, S. J., Aldini, S. T., Snyder, J. E.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.2834721

Ga-substituted cobalt ferrite oxides show promise as high magnetostriction, high sensitivity magnetoelastic materials for sensor and actuator applications, but their atomic-level behavior is not yet well understood. In this study, the magnetic environments of the Fe atoms in Ga-substituted cobalt ferrite have been investigated using Mossbauer spectroscopy. A series of five powder samples with Co Ga x Fe 2 − x O 4 compositions ( x = 0.0 - 0.8 ) was investigated using transmission geometry. Results show two distinct six-line hyperfine patterns, which are identified as Fe in A (tetrahedral) and B (octahedral) spinel sites. Increasing Ga concentration is seen to decrease the hyperfine field strength for both A and B sites, as well as increasing the width of those distributions, consistent with the nonmagnetic nature of Ga 3 + ions. Effects are more pronounced for the B sites than the A sites. Results for Ga substitution show more pronounced effects than for previous studies with Cr 3 + or Mn 3 + substitution: the hyperfine fields decrease and distribution widths increase at greater rates, and the differences between A and B site behavior are more pronounced. Results indicate that at least for the lower Ga concentrations, the Ga 3 + ions substitute predominantly into the A sites, in contrast to Cr 3 + and Mn 3 + which substitute into the B sites. This interpretation is supported by measurements of magnetization at low temperatures.