Magnetic and magnetoelastic properties of Ga-substituted cobalt ferrite

Abstract

Magnetic and magnetoelasticproperties of a series of Ga-substituted cobaltferrites,CoGaxFe2−xO4 (x=0.0-0.8), have been investigated. The Curie temperatureTCand hysteresis properties were found to vary with gallium content (x), which indicates that exchange and anisotropy energies changed as a result of substitution of Ga for Fe. The maximum magnitude of magnetostriction decreased monotonically with increasing gallium content over the range x=0.0-0.8. The rate of change of magnetostriction with applied magnetic field (dλ/dH) showed a maximum value of 3.2×10−9A−1m for x=0.2. This is the highest value among recently reported cobaltferrite based materials. It was found that the dependence of magnetic and magnetoelasticproperties on the amount of substituent (x) was different for Mn, Cr, and Ga. This is considered to be due to the differences in cation site occupancy preferences of the elements within the spinel crystal structure: Mn3+ and Cr3+ prefer the octahedral (B) sites, whereas Ga3+ prefers the tetrahedral (A) sites. KeywordsAmes Laboratory, CNDE, Cobalt, Ferrites, Magnetostriction, Magnetic anisotropy, Curie point Disciplines Materials Science and Engineering CommentsThe following appeared in Journal of Applied Physics 101 ( Magnetic and magnetoelastic properties of a series of Ga-substituted cobalt ferrites, CoGa x Fe 2−x O 4 ͑x = 0.0-0.8͒, have been investigated. The Curie temperature T C and hysteresis properties were found to vary with gallium content ͑x͒, which indicates that exchange and anisotropy energies changed as a result of substitution of Ga for Fe. The maximum magnitude of magnetostriction decreased monotonically with increasing gallium content over the range x = 0.0-0.8. The rate of change of magnetostriction with applied magnetic field ͑d / dH͒ showed a maximum value of 3.2ϫ 10 −9 A −1 m for x = 0.2. This is the highest value among recently reported cobalt ferrite based materials. It was found that the dependence of magnetic and magnetoelastic properties on the amount of substituent ͑x͒ was different for Mn, Cr, and Ga. This is considered to be due to the differences in cation site occupancy preferences of the elements within the spinel crystal structure: Mn 3+ and Cr 3+ prefer the octahedral ͑B͒ sites, whereas Ga 3+ prefers the tetrahedral ͑A͒ sites.

Magnetic and magnetostrictive properties of aluminium substituted cobalt ferrite synthesized by citrate-gel method

“…However, the highest maximum strain obtained for the sample is very low as 150 ppm. Enhancement in the strain sensitivity is reported after substitution of metal ions in the cobalt ferrite lattice, but at the cost of the magnetostriction strain [13][14][15][16][17]. It has been shown that the strain sensitivity can be enhanced, without affecting the magnetostriction coefficient, for sintered Mn-substituted cobalt ferrite made from nanosized powders [18].…”

“…4 shows the variation of the saturation magnetization (M s ), at room temperature as well as at 5 K, as a function of the Al content in CoFe 2-x Al x O 4 . Saturation magnetization is obtained by extrapolating the [14,22] in cobalt ferrite reduces the net magnetization of the A-site at a greater magnitude than at the B-site. At higher concentrations of the substituted ions, the overall magnetization decreases due the migration of the non-magnetic ions into the B-sites.…”

Dielectric relaxations and alternating current conductivity in manganese substituted cobalt ferrite

“…Substitution of other metals for Fe in cobalt ferrite has been proposed to tailor the electrical, magnetic, and magnetomechanical properties of such materials. [14][15][16][17][18][19][20][21][22][23] In this context, partial replacement of Fe 3þ by rare earth or large ionic radius ion in the spinel structure has been reported to lead to structural distortion, which induces strain and significantly modifies the electrical properties. [14][15][16] The structural, magnetic, electrical, and dielectric properties of Co ferrites play a key role in the designing of magnetic, electronic, microwave, and electrochemical devices.…”

Influence of vacuum sintering on microstructure and magnetic properties of magnetostrictive cobalt ferrite

“…Since the magnetostrictive properties of CoFe 2 O 4 depend largely on the position and concentration of the Co 2+ ions, it follows that changes in the site occupancy of these ions will affect the magnetic and magnetostrictive properties of CoFe 2 O 4 . Studies have shown that magnetic and magnetostrictive properties can be altered by both chemical substitutions of the cations [4][5][6] and by heat treatment [7,8], the latter leading to a different distribution of cations as they migrate towards their most stable (that is the lowest energy) state. The time constants associated with this process are prohibitively long at room temperature, but are reduced at elevated temperature because of the higher thermal energy per ion which enables them to migrate more easily.…”