Crystal strain, chemical bonding, magnetic and magnetostrictive properties of erbium (Er³⁺) ion substituted cobalt-rich ferrite (Co₁.₁Fe₁.₉₋ₓErₓO₄)
2016
Kakade, S. G. | Kambale, R. C. | Ramanna, C. V. | Kolekar, Y. D.
Erbium (Er) substituted nanocrystalline cobalt-rich Co₁.₁Fe₁.₉₋ₓErₓO₄ (x = 0.00–0.20) has been synthesized by the sol gel auto-combustion method. The crystal structure with induced strain, chemical bonding, magnetic and magnetostrictive properties of Co₁.₁Fe₁.₉₋ₓErₓO₄ have been studied as a function of the Er content. X-ray diffraction results confirmed the pure phase formation of the spinel cubic lattice for erbium (Er) substitution up to x ≤ 0.10; for x ≥ 0.15, a small amount of secondary orthoferrite phase ErFeO₃ begins to form, in addition to the required Co₁.₁Fe₁.₉₋ₓErₓO₄. Erbium substitution for Fe in Co₁.₁Fe₁.₉O₄ introduces strain due to its larger ionic radius which is also supported by the red shift observed in Raman spectra. All the samples show typical magnetic hysteresis behavior with a decrease in magnetization due to the weak superexchange interaction and an increase in coercivity as a function of Er content. The maximum values of the magnetostriction coefficient (λ₁₁ = −210 ppm at 2.2 kOe) and strain derivative (dλ/dH = 327 × 10³ ppm Oe⁻¹) are obtained for Er, x = 0.05. The decrease in Curie temperature from 455 °C to 378 °C, with Er content, indicates the decrease in strength of the overall A–B superexchange coupling of Co₁.₁Fe₁.₉₋ₓErₓO₄. The magnetic and magnetostrictive properties authenticate the significance of the prepared samples for memory storage and stress sensing applications.
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