Effect of High-Anisotropic Co²⁺ Substitution for Ni²⁺ on the Structural, Magnetic, and Magnetostrictive Properties of NiFe₂O₄: Implications for Sensor Applications

Abstract

This work reports on the effect of substituting a low-anisotropic and low-magnetic cation (Ni 2+ , 2μ B ) by a high-anisotropic and high-magnetic cation (Co 2+ , 3μ B ) on the crystal structure, phase, microstructure, magnetic properties, and magnetostrictive properties of NiFe 2 O 4 (NFO). Co-substituted NFO (Ni 1−x Co x Fe 2 O 4 , NCFO, 0 ≤ x ≤ 1) nanomaterials were synthesized using glycine-nitrate autocombustion followed by postsynthesis annealing at 1200 °C. The X-ray diffraction measurements coupled with Rietveld refinement analyses indicate the significant effect of Co-substitution for Ni, where the lattice constant (a) exhibits a functional dependence on composition (x). The a-value increases from 8.3268 to 8.3751 Å (±0.0002 Å) with increasing the "x" value from 0 to 1 in NCFO. The a−x functional dependence is derived from the ionic-size difference between Co 2+ and Ni 2+ , which also induces grain agglomeration, as evidenced in electron microscopy imaging. The chemical bonding of NCFO, as probed by Raman spectroscopy, reveals that Co(x)-substitution induced a red shift of the T 2g (2) and A 1g (1) modes, and it is attributed to the changes in the metal−oxygen bond length in the octahedral and tetrahedral sites in NCFO. X-ray photoelectron spectroscopy confirms the presence of Co 2+ , Ni 2+ , and Fe 3+ chemical states in addition to the cation distribution upon Co-substitution in NFO. Chemical homogeneity and uniform distribution of Co, Ni, Fe, and O are confirmed by EDS. The magnetic parameters, saturation magnetization (M S ), remnant magnetization (M r ), coercivity (H C ), and anisotropy constant (K 1 ) increased with increasing Co-content "x" in NCFO. The magnetostriction (λ) also follows a similar behavior and almost linearly varies from −33 ppm (x = 0) to −227 ppm (x = 1), which is primarily due to the high magnetocrystalline anisotropy contribution from Co 2+ ions at the octahedral sites. The magnetic and magnetostriction measurements and analyses indicate the potential of NCFO for torque sensor applications. Efforts to optimize materials for sensor applications indicate that, among all of the NCFO materials, Co-substitution with x = 0.5 demonstrates high strain sensitivity (−2.3 × 10 −9 m/A), which is nearly 2.5 times higher than that obtained for their intrinsic counterparts, namely, NiFe 2 O 4 (x = 0) and CoFe 2 O 4 (x = 1).

3D Hierarchical MOF-Derived Defect-Rich NiFe Spinel Ferrite as a Highly Efficient Electrocatalyst for Oxygen Redox Reactions in Zinc–Air Batteries

“…This discovery occurred due to the electronic interaction of the Fe and Ni atoms. In Figure e, the O 1s spectrum reveals three deconvoluted peaks at 530.1, 532.0, and 533.7 eV . The Ni/Fe–O and ketonic C–O groups are represented by two major peaks at 530.1 and 532.0 eV, respectively.…”

Synthesis and Self-Assembly of Nickel-Substituted Ferrite Nanoparticles with Controlled Morphology and Chemical Composition

“…This shift is attributed to the relatively smaller radii of Ni 2+ ions (0.69 Å) compared to Fe 2+ ions (0.77 Å). , The substitution of Ni 2+ ions for Fe 2+ ions in the lattice results in a decrease in the lattice constant, leading to increased diffraction angles and rightward shifting of peaks. This observation confirms the successful incorporation of the substituted Ni 2+ ions into the lattice, resulting in the formation of a perfect solid solution with a single-phase material …”

“…EDS analysis confirmed the presence of Ni and Fe elements, as shown in Figure a. Since EDS is a localized measurement technique for element proportions, ICP-AES was conducted to ensure the reliability of the experiments. The molar ratio of Ni and Fe elements obtained from ICP-AES allowed the determination of the chemical composition of the samples.…”

“…Ferrite, a traditional material, has gained considerable attention recently due to the use of different cations, like zinc, manganese, cobalt, and nickel, as substitutes. − In recent years, various synthesis procedures have been employed to synthesize ferrites (MFe 2 O 4 ) with different metallic cations. ,− Notably, nickel ferrite nanoparticles, possessing an inverse spinel structure, exhibit desirable properties, including high electrical resistivity, low magnetic coercivity, excellent chemical stability, and affordability . These properties make them an ideal choice for micro-/nano-functional devices, such as microscale sensors and on-chip electromagnetic devices.…”

Aluminum and Zinc Co-substituted Cobalt Ferrite: Structural, Magnetic, and Magnetostrictive Properties

“…Ferri- and ferromagnetic materials, which exhibit magnetostriction, received considerable interest from the scientific and engineering community for research and development activities. − Magnetostriction, which is the change in dimension of a magnetic material in the magnetic field, is considered a smart phenomenon, and materials that can exhibit magnetostriction are considered smart materials. ,− Cobalt ferrite (CoFe 2 O 4 ; CFO) is one of the widely known magnetostrictive smart materials. − Due to its high magnetostriction strain (λ), which exists in both single-crystal and polycrystalline forms, CFO and CFO-based composites constitute extensively studied ceramic magnetostrictive smart materials. ,,,,− Because of their exceptional magnetic and magnetostrictive properties, CFO and CFO-based composites find application as sensors in a variety of systems. , Additionally, CFO has been investigated as an active ingredient for multiferroic particulate composites composed of magnetostrictive and piezoelectric phases. , …”