Effect of size and site preference of trivalent non-magnetic metal ions (Al³⁺, Ga³⁺, In³⁺) substituted for Fe³⁺on the magnetostrictive properties of sintered CoFe₂O₄

Abstract

The influence of size and crystallographic site preference of three non-magnetic isovalent metal ions of larger (In 3+ ), comparable (Ga 3+ ) and smaller (Al 3+ ) sizes, substituted for Fe 3+ in the spinel lattice of CoFe 2 O 4 on its magnetostrictive properties is compared. For the different compositions in CoFe 2−x M x O 4 (M = In 3+ , Ga 3+ , Al 3+ and 0 ⩽ x ⩽ 0.3), significant changes in the structural and magnetic parameters are observed with the degree of substitution, due to the size and site preferences. Magnetic and Raman spectral studies revealed that Al 3+ is substituted for Fe 3+ at both octahedral and tetrahedral sites for all compositions, whereas In 3+ and Ga 3+ are substituted for Fe 3+ at the tetrahedral site only for x ⩽ 0.2 and partly at the octahedral site for x > 0.2. Regardless of the differences in the ionic size, site preference and the magnetic properties, compositions in all three series with x = 0.1 showed almost equal magnitude of maximum magnetostriction (λ max = ~230 ppm), marginally higher than that of x = 0 (217 ppm). However, at higher substituted compositions, λ max is decreased with x, but the decrease is much faster for the Al-substituted compositions. The maximum strain sensitivity, [dλ/dH] max , is also found to be comparable for all three compositions. The comparable magnetostriction characteristics and high strain at low magnetic fields for different substituted compositions at low levels of substitution are attributed to the local structural distortions associated with the inhomogeneous distribution of the substituted ions in the spinel ferrite lattice. The studies suggest ways to optimise the magnetostriction properties of properly substituted sintered cobalt ferrite for applications in sensors and actuators.

Dynamic Magnetostriction of CoFe2O4 and Its Role in Magnetoelectric Composites

“…This can be done by magnetic annealing [11][12][13][14][15], magnetic-field-assisted compaction [16,17], or reaction under uniaxial pressure [18]. Another way to tune magnetostrictive properties of CoFe 2 O 4 is by substitution of the Fe atoms by Mg, Al, Ti, Mn, Ni, Cu, Zn, Ga, Zr, Nb, In, etc., or even rare-earth elements [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. Moreover, there is an increasing interest in synthesizing cobalt ferrite from recycled Li-ion batteries to use it in magnetostrictive applications [25,[34][35][36].…”

Ga2.52V2·48O7·33(OH)0.67, a synthetic member of the nolanite/akdalaite-type family of oxyhydroxides containing trivalent vanadium

“…The refined chemical composition Ga2.52V2.48O7.33(OH)0.67 gives a refined composition close to Ga:V as 1:1 which is in good agreement with both the stoichiometry of the reaction and the metal ratio as inferred from both EDX from electron microscopy and ICP-OES analysis. In addition to this, the tetrahedral site is exclusively occupied by gallium, which is not unexpected owing to the tetrahedral site preference shown by gallium in many oxide materials [23][24][25][26]. The octahedral sites are occupied by both gallium and vanadium.…”

The Phase Diagram and Exotic Magnetostrictive Behaviors in Spinel Oxide Co(Fe1−xAlx)2O4 System

“…Figure 1d shows the calculated lattice constant for each composition. The radius of Al 3+ is smaller than Fe 3+ and Co 2+ , so with the increasing content of Al, the lattice constant decreases monotonously [15,18].…”

“…The nanocrystalline Al-doped CoFe 2 O 4 powders fabricated via the sol–gel auto-ignition method were also studied systematically, indicating that the nanocrystalline Al-doped CoFe 2 O 4 is a good candidate for high frequency applications [13,14]. Anantharamaiah and Joy investigated the site preference of Al in CoFe 2 O 4 and concluded that Al 3+ substitutes Fe 3+ at both crystallographic sites (A-site and B-site) [15].…”