Tailoring Magnetic Properties of Fe0.65Co0.35 Nanoparticles by Compositing with RE2O3 (RE = La, Nd, and Sm).

Fe-Co alloys are the most important soft magnetic materials, which are successfully used for a wide range of applications. In this work, the magnetic properties of lanthanide-substituted (Fe0.65Co0.35)0.95(RE2O3)0.05 (RE = La, Nd, and Sm) nanoparticles, prepared by mechanical alloying, are reported. Our comprehensive studies (X-ray diffraction, Mössbauer spectroscopy, scanning electron microscopy with X-ray energy dispersive spectrometry, SQUID magnetometry and differential scanning calorimetry) have revealed different properties, depending on the dopant type. The RE2O3 addition led to a decrease in the crystallite size and to an increase in the internal microstrain. Moreover, because of the high grain fragmentation tendency of RE2O3, the cold welding between Fe-Co ductile particles was minimized, indicating a significant decrease in the average particle size. The parent Fe0.65Co0.35 alloy is known for its soft ferromagnetism. For the La-substituted sample, the magnetic energy product was significantly lower (0.450 MG·Oe) than for the parent alloy (0.608 MG·Oe), and much higher for the Sm-substituted compound (0.710 MG·Oe). The processing route presented here, seems to be cost-effective for the large-scale production of soft magnetic materials.

Structure, Morphology, Heat Capacity, and Electrical Transport Properties of Ti3(Al,Si)C2 Materials.

A study of Ti3Al1-xSixC2 (x = 0 to x = 1) MAX-phase alloys is reported. The materials were obtained from mixtures of Ti3AlC2 and Ti3SiC2 powders with hot pressing sintering technique. They were characterised with X-ray diffraction, heat capacity, electrical resistivity, and magnetoresistance measurements. The results show a good quality crystal structure and metallic properties with high residual resistivity. The resistivity weakly varies with Si doping and shows a small, positive magnetoresistance effect. The magnetoresistance exhibits a quadratic dependence on the magnetic field, which indicates a dominant contribution from open electronic orbits. The Debye temperatures and Sommerfeld coefficient values derived from specific heat data show slight variations with Si content, with decreasing tendency for the former and an increase for the latter. Experimental results were supported by band structure calculations whose results are consistent with the experiment concerning specific heat, resistivity, and magnetoresistance measurements. In particular, they reveal that of the s-electrons at the Fermi level, those of Al and Si have prevailing density of states and, thus predominantly contribute to the metallic conductivity. This also shows that the high residual resistivity of the materials studied is an intrinsic effect, not due to defects of the crystal structure.