Crystal strain, chemical bonding, magnetic and magnetostrictive properties of erbium (Er3+) ion substituted cobalt-rich ferrite (Co1.1Fe1.9-xErxO4)

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 (lambda(11) = -210 ppm at 2.2 kOe) and strain derivative (d lambda/dH = 327 x 10(3) ppm Oe(-1)) are obtained for Er, x = 0.05. The decrease in Curie temperature from 455 degrees C to 378 degrees 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.