Tailoring the magnetic properties of cobalt-ferrite nanoclusters

Remanence Plots as a Probe of Spin Disorder in Magnetic Nanoparticles

“…15,[17][18][19][20][21] Given the crucial importance of interactions in magnetic nanostructures, many direct and indirect approaches have been used to try to quantify them: first order reversal curve (FORC) analysis, 22,23 small angle neutron scattering, SANS, [24][25][26][27] electron holography, 28,29 magnetic force microscopy, 30,31 Lorentz microscopy, 32 Brillouin light scattering, 33 resonant magnetic x-ray scattering 34 and so on. However, one of the most accepted methods to assess interactions is the remanence plots technique (i.e., Henkel or δM plots), [35][36][37] which is routinely used to evaluate interactions between nanoparticles or grains [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] both in fundamental studies 56,57 and in diverse nanoparticle-based applications (e.g., patterned recording media, permanent magnets, or magnetic resonance imaging 11,38,…”

“…69 However, even in the uniaxial anisotropy case, the fact that magnetic single-phase and core/shell nanoparticles (particularly oxide nanoparticles) are usually not monodomains (i.e., cannot be simplified to a system of macro-spins), often exhibiting rather complex internal spin structures, 70-74 may cast some doubts over the validity of the remanence curves approach for the evaluation of dipolar interactions. [44][45][46][47][48][49][50][51][52][53][54][75][76][77] Here we investigate the interactions in γ-Fe 2 O 3 nanoparticles coated by thick SiO 2 shells (up to 62 nm) via δM plots and FORC. The δM plots show clear negative dips, apparently implying dipolar interactions, even in the extremely magnetically dilute cases.…”

“…Exchange and dipolar interactions between grains or particles are essential to understanding the behavior of magnetic polycrystalline and colloidal materials. , Indeed, these interactions are key to the performance of many common magnetic materials, e.g., permanent magnets, , magnetic recording media, , and magnetically soft materials for high frequency applications, where dipolar interactions may have undesirable effects, such as aggregation of nanoparticles in biomedical applications. − Magnetic interactions control the properties of sufficiently dense assemblies of magnetic nanoparticles and nanostructures, tailoring their functional properties, e.g., blocking (or freezing) temperature, coercivity, remanent magnetization, switching-field distribution, and effective anisotropy, among others. − In fact, interactions are the basis of a large number of nanoparticle-based magnetic materials, e.g., superferromagnets, superspin glasses, artificial spin ice, long-range self-assemblies, or ferrofluids. ,− Given the crucial importance of interactions in magnetic nanostructures, many direct and indirect approaches have been used to try to quantify them: first-order reversal curve (FORC) analysis, , small angle neutron scattering, SANS, − electron holography, , magnetic force microscopy, , Lorentz microscopy, Brillouin light scattering, resonant magnetic X-ray scattering, and so on. However, one of the most accepted methods to assess interactions is the remanence plots technique (i.e., Henkel or δM plots), − which is routinely used to evaluate interactions between nanoparticles or grains − both in fundamental studies , and in diverse nanopar...…”

The effect of agarose content on the morphology, phase evolution, and magnetic properties of CoFe2O4 nanoparticles prepared by sol‐gel autocombustion method

“…7-10 Based on these excellent properties, CoFe 2 O 4 is used in high frequency magnets, microwave absorbers, magnetic catalysis, magnetic bulk cores, magnetic resonance imaging, and drug delivery. 8,11 The CoFe 2 O 4 NPs have been synthesized by various methods including coprecipitation, [12][13][14][15][16] microemulsion, [17][18][19][20] mechanical alloying, [21][22][23] hydrothermal, [24][25][26][27][28][29][30] and sol-gel autocombustion. [31][32][33][34][35] Among these methods, sol-gel method offers a flexible approach to obtaining a diverse range of materials without use of expensive processing technologies, such as vacuum methods.…”

Pitfalls and Challenges in Nanotoxicology: A Case of Cobalt Ferrite (CoFe2O4) Nanocomposites

“…However, the most used method is the coprecipitation method because of its simplicity, use of less hazardous chemicals with stable monodispersed suspension, uniform size distribution, and better magnetic properties for safe use in nanomedicine . The details of the different synthesis routes and their respective advantages and disadvantages are out of the scope of this review, but the readers may find different methods of synthesis elsewhere. − …”