E. Skoropata

Tuning the surface magnetism of γ-Fe2O3 nanoparticles with a Cu shell

An interfacial monolayer of CuO in Cu-coated γ-Fe2O3 nanoparticles enables significantly decreased intrinsic surface spin disorder compared to bare γ-Fe2O3 nanoparticles. Element specific x-ray absorption spectroscopy at the L-edges for Cu and Fe indicates that the magnetic moment of the CuO in the shell interacts with the γ-Fe2O3 nanoparticle’s surface magnetic moments. This exchange interaction cants the moments of the CuO resulting in a non-zero Cu moment, altering the γ-Fe2O3 nanomagnetism.

Modification of the ferromagnetic anisotropy and exchange bias field of NiFe/CoO/Co trilayers through the CoO spacer thicknesses

We have investigated the magnetism of NiFe/CoO/Co trilayers with different CoO spacer thicknesses. The dependence of the coercivity (Hc) and exchange bias field (Hex) on the CoO thicknesses indicated that different pinning strengths from the CoO were acting on the top NiFe and bottom Co layers, respectively. DC susceptibility indicated the different interlayer coupling energies and showed that the anisotropy of CoO layer strongly affected the temperature dependence of the magnetization.

Structure and composition of iron nanoparticles synthesized using a novel anionic-element complex

We use a novel solution-based disassociation synthesis scheme of the ionic complex Fe(LiBH4)2 to form Fe nanoparticles. The complex was formed initially using a gentle mechanochemical process, and the Fe nanoparticles emerged after 4 h of ball milling in an air-free environment. Rietveld refinement of x-ray diffraction measurements in an air-free sample holder identified a Im 3¯m α-Fe phase. A room temperature Mossbauer spectrum of the sample presented a six-line spectrum unique to Fe0 metal, and the Fe nanoparticles were extremely well crystallized. Magnetometry results presented a reduced saturation magnetization (e.g., Ms∼ 85u2009emu/g at 50u2009K) that had a Bloch-like T2 temperature dependence, consistent with a gap in the magnon fluctuation spectrum due to finite-size effects. The Fe nanoparticles were magnetically soft, with a coercivity ranging from ∼10 to 20u2009mT with decreasing temperature from 350u2009K.