Determining magnetic nanoparticle size distributions from thermomagnetic measurements

Abstract

Thermomagnetic measurements are used to obtain the size distribution and anisotropy of magnetic nanoparticles. An analytical transformation method is described which utilizes temperaturedependent zero-field cooling magnetization data to provide a quantitative measurement of the average diameter and relative abundance of superparamagnetic nanoparticles. Applying this method to self-assembled MnAs nanoparticles in MnAs-GaAs composite films reveals a log-normal size distribution and reduced anisotropy for nanoparticles compared to bulk materials. This analytical technique holds promise for rapid assessment of the size distribution of an ensemble of superparamagnetic nanoparticles.

Structural and magnetic characteristics of MnAs nanoclusters embedded in Be-doped GaAs

“…We now compare our materials to those studied in previous work 17, 21 by carrying out a statistical survey of the diameters of these (assumed spherical) nanoclusters in both the Type I material and the Type II material. Figure 12 shows the data compiled by measuring the diameters of the clusters in HRXTEM images and plotting the normalized number of clusters versus their diameter D. After this, we applied a log-normal fit to the plot to determine the distribution's width σ and the median cluster diameter for the sample D 0 .…”

Numerical analysis of compression mechanics of highly polydisperse granular mixtures with different PSD-s

“…Normal and lognormal PSDs are often assumed in descriptions of the random variation that occurs in the data from many scientific disciplines [18][19][20] and in descriptions of granular materials, which are important in many industrial and natural processes (e.g., seeds, grains, sands, gravel, powders). In the majority of investigations performed on granular materials, the Gaussian (normal) or log-normal PSDs, which represent continuous unimodal symmetric and asymmetric PSDs, respectively, have been applied.…”

Size distribution of FeNiB nanoparticles

“…This procedure was successful in determination of magnetic unit sizes in different systems, from magnetic nanoparticles [14,15,16], to magnetic clusters in amorphous ribbon [17] and magnetic nano-regions in multiferroics. [18] Therefore, we believe this model is valid in case of presented amorphous nanoparticles.…”

“…Since ZFC M(T) measurements count how many magnetic moments are unblocked up to temperature T, i.e. for what amount of magnetization this T is equal to T B , the distribution of blocking temperatures in the sample is revealed as f(T B ) ~ d(T·M ZFC (T))/dT (for details see [2,14]). Assuming spherical particles,…”