Ferroic ordering and charge‐spin‐lattice order coupling in Gd‐doped Fe₃O₄ nanoparticles relaxor multiferroic system

Abstract

We investigated the effect of gadolinium doping (1-5 at.%) on the magnetic and dielectric properties of Fe 3 O 4 nanoparticles, synthesized by the chemical co-precipitation technique, primarily to understand the onset of multifunctional properties such as ferroelectricity and magnetodielectric coupling. The substitution of larger Gd 3+ ions at smaller Fe 3+ octahedral sites in inverse spinel Fe 3 O 4 has significantly influenced the morphology, average crystallite size, and more importantly, the magneto-crystalline anisotropy and saturation magnetization. The magnetocrystalline anisotropy and the saturation magnetization decreases substantially, however, significant increase in the average crystallite size is observed upon Gd doping. Furthermore, temperature-dependent dielectric studies suggest that these nanoparticle systems exhibit relaxor ferroelectric behavior, with much pronounced ferroelectric polarization moment recorded for 5 at.% Gd doped Fe 3 O 4 as compared to its undoped counterpart. K E Y W O R D Sferrites, ferroelectricity/ferroelectric materials, ferromagnetism/ferromagnetic materials, magnetoelectrics Suvra S. Laha and Ehab Abdelhamid contributed equally for this work.

Rare‐Earth Doped Iron Oxide Nanostructures for Cancer Theranostics: Magnetic Hyperthermia and Magnetic Resonance Imaging

“…The Fe 3 O 4 nanoparticles and their RE doped counterparts are mostly synthesized using the chemical coprecipitation technique. [31,32,42,70,89,[106][107][108][109][110] In this technique, the iron salts, primarily chlorides, sulfates or nitrates are used as the precursors along with sodium, potassium, or ammonium hydroxides as the precipitating agent. As the spinel structure of Fe 3 O 4 contains Fe 2+ and Fe 3+ ions, both the ferrous and ferric salts in suitable proportion, maintaining a molar ratio of 1:2, are mixed to form a solution as the precursor.…”

“…Subsequently, the OHions of concentration in the range of ≈1-5 m are added drop-wise or slowly to the mixture containing iron salts with continuous stirring at room temperature. [31,32,42,89,110] The reaction is preferred to be conducted in an inert environment, particularly in the presence of Ar or N 2 flow, to prevent any unwanted oxidation of the as-synthesized Fe 3 O 4 nanoparticles. The reaction mechanism is as follows: [111]…”

“…have been implemented as the primary dopant materials. [31,32,42,70,89] The sequence in which the dopants are added to the iron salts critically determines which sites, octahedral or tetrahedral, they will occupy and furthermore dictates both structural and magnetic properties. [31,32] This method is highly cost-effective and can be employed for the large-scale synthesis of nanoparticles with a size less than 20 nm.…”

“…[3,4,6] In addition, the magnetic properties of superparamagnetic nanoparticles depend on nanoparticle crystallite size, shape, and geometry. Therefore, researchers turned their attention on the fabrication of pure Fe 3 O 4 (magnetite) with tunable sizes and shapes, and its derivatives starting from core-shell geometries, [10][11][12][13][14][15][16][17][18][19] nanocomposites [20][21][22][23][24][25][26][27][28] to doped systems [29][30][31][32][33][34][35] having interesting magnetic, dielectric and chemical properties and applied them for advanced technological and biomedical applications. For example, bulk magnetite exhibits a saturation magnetization (M S ) of about 92 emu g -1 .…”

“…[6] At room temperature, PEGlyted Fe 3 O 4 nanoparticles with an average diameter of about 4 nm exhibit a M S of 34 emu g -1 , [35] whereas for 12 nm sized particles, the values of M S usually hover between 65 and 70 emu g -1 . [31,32] In addition, with further decreasing the particle size, the surface effects will become more dominant with enhanced spin disorder, and accordingly, the saturation magnetization may diminish at room temperature, giving rise to a paramagnetic state. [37] Over the years, the doping strategy has been widely adopted for tuning the properties of iron oxide nanoparticles.…”