Tuning the Magnetic Properties of Nanoparticles

Abstract

The tremendous interest in magnetic nanoparticles (MNPs) is reflected in published research that ranges from novel methods of synthesis of unique nanoparticle shapes and composite structures to a large number of MNP characterization techniques, and finally to their use in many biomedical and nanotechnology-based applications. The knowledge gained from this vast body of research can be made more useful if we organize the associated results to correlate key magnetic properties with the parameters that influence them. Tuning these properties of MNPs will allow us to tailor nanoparticles for specific applications, thus increasing their effectiveness. The complex magnetic behavior exhibited by MNPs is governed by many factors; these factors can either improve or adversely affect the desired magnetic properties. In this report, we have outlined a matrix of parameters that can be varied to tune the magnetic properties of nanoparticles. For practical utility, this review focuses on the effect of size, shape, composition, and shell-core structure on saturation magnetization, coercivity, blocking temperature, and relaxation time.

A quantitative study of particle size effects in the magnetorelaxometry of magnetic nanoparticles using atomic magnetometry

“…One may assume that the larger particles have a multidomain structure, whose ferromagnetic behaviour is not described by our model. However, we can rule out this hypothesis since maghemite is known [34] to exist in single domain forms up to radii r 35 nm 〈 〉 ∼ , larger than the particles in our experiments.…”

“…(34) and (37) it follows that the fit parameter a ∼ is proportional to total mass of the nanoparticles m tot : (Table 4). This observation shows that the samples contain particles that either do not produce a magnetic field or whose magnetisation does not relax according to the MSM decay law.…”

Selective Magnetic Evolution of MnxFe1–xO Nanoplates

“…1 The decrease of saturation magnetization follows, but the compensation is that the increased coercivity can be used for many applications from biomedical to magnetic storage technology. [2][3][4] One of the explored methods is the hybridization of soft ferrites with hard magnets, 5 for example, hard ferrite magnet CoFe 2 O 4 as cores with MnO shell. 6 This method in some materials requires additional annealing step to obtain desired coercivity and magnetization, as seen in tetrahedral FePt from as-synthesized cubic phase.…”

Cobalt Ferrite Nanoparticles Fabricated via Co-precipitation in Air: Overview of Size Control and Magnetic Properties

“…Inverse spinels are ferrimagnetic because, for the inverse spinel structure, the magnetic moments of the cations in the octahedral sites align themselves to be parallel to an applied magnetic field, and the magnetic moments of the cations in the tetrahedral sites align themselves to be antiparallel to an applied magnetic field [12]. On account of this, the specific value of the magnetic moment of inverse spinel compounds depends on the cations involved, which in this case are Cobalt (Co 2+ ) and Iron (III) (Fe 3+ ) [12].…”

“…On account of this, the specific value of the magnetic moment of inverse spinel compounds depends on the cations involved, which in this case are Cobalt (Co 2+ ) and Iron (III) (Fe 3+ ) [12]. On a more macro level, as we previously described, there are twice as many occupied octahedral sites as there are occupied tetrahedral sites, and therefore, in an applied magnetic field, the unit cell acquires a net magnetization which is parallel to the applied magnetic field [35].…”