Morphologic and magnetic properties of Pd100−xFex nanoparticles prepared by ultrasound assisted electrochemistry

Abstract

Nanopowdered alloys of Pd100−xFex, with x=4, 6, 8, and 12, have been prepared by ultrasound assisted electrochemistry. The composition of the individual particles, as determined by x-ray fluorescence, and the bulk composition, as determined by atomic absorption, are in agreement within experimental error. Transmission electron microscopy indicates that the nanopowders consist of agglomerates of small grains with a radius of approximately 5 nm, a radius which is confirmed by the broadening of the reflections in the x-ray powder diffraction patterns. X-ray fluorescence analysis of individual grains indicates a homogeneous distribution of palladium and iron throughout the grains. The x-ray diffraction patterns indicate that solid solutions of iron in palladium show no evidence of any pure palladium, any pure iron, or any other PdFe compound. The 78 K iron-57 Mössbauer spectra of these nanopowders reveal the presence of one magnetic sextet assigned to slowly relaxing superparamagnetic particles of Pd100−xFex and one weak doublet, which is assigned to rapidly relaxing superparamagnetic particles of Pd100−xFex. The hyperfine fields of 29.0 to 31.0 T are typical of iron in a metallic alloy and correspond to a magnetic moment of approximately 2 μB per iron atom. The hysteresis curves obtained at 4.2, 100, and 295 K with a vibrating sample magnetometer are typical of superparamagnetic particles with saturation magnetization values which are substantially smaller than those observed for the bulk. The fit of the magnetization curves with a Langevin function yields estimates of the particle radii which are in good agreement with those obtained both by transmission electron microscopy and by the broadening of the x-ray diffraction peaks.

Magnetic Modulation: Atomic CN and Thermal Coupling

“…Repeating the same Stern-Gerlach deflections of Fe clusters in a molecular beam, Heer et al [8] found instead that the average magnetic moments for small iron clusters (50-230 atoms) drops with the number of atoms when the molecular beam nozzle temperatures are around 300 K. This trend is similar to those observed at room temperature of Co [11], Pd 96 Fe 4 [9,10] [33] and Ni thin films has been observed at room temperature [6,34]. The M S for Fe 3 O 4 thin films [35] drops rapidly when the film decreases from 70 nm.…”

“…Figure 19.1c and d shows the magnetic suppression of Co clusters [11,18] and Ni films. Small Pd 100-x Fe x , grains with x = 4, 6, 8, 12 and a radius of approximately 5 nm at 4.2, 100, and 295 K show typical superparamagnetic features with M S values that are substantially smaller than those observed for the bulk [9]. However, for MnBi films [37], the magnetic momentum changes with neither thickness nor chemical composition.…”

“…However, controversy remains in the measured trend of the M S (K) values [8][9][10][11][18][19][20][21]. One trend in measurement [29] and b Rh n [30] particles measured at low temperature shows the size-enhanced and quantized M S (N) with oscillating features, c cobalt particles [11] and d Ni thin films [6] measured at room temperature show sizetailed M S (K), instead (reprinted with permission from [31]) shows that at temperatures below 200 K, the M S (K) increases with the inverse of size [21][22][23][24][25].…”

Size dependence of nanostructures: Impact of bond order deficiency

“…Fig. 41c and d shows the magnetic suppression of Co clusters [632,637] [630]. However, for MnBi films [653], the magnetic momentum changes with neither thickness nor chemical composition.…”

Sonoelectrochemical (20 kHz) production of Co65Fe35 alloy nanoparticles from Aotani solutions

“…They showed that, during cavitation, a jet of liquid penetrates inside the cavitation bubble perpendicular to the 'sonoelectrode' surface [16] and the resulting impact was responsible for dislodging any nanopowder material which had been electrochemically deposited on the surface. This new sonoelectrochemical method has since been employed to produce several pure metallic, alloy [14,[20][21][22] and semiconductor nanoparticles [23][24][25][26].…”