Title :
Effect of Si doping on the electron spin resonance properties of ferrihydrite nanoparticles
Author :
Seehra, M.S. ; Punnoose, A. ; Roy, P. ; Manivannan, A.
Author_Institution :
Dept. of Phys., West Virginia Univ., Morgantown, WV, USA
fDate :
7/1/2001 12:00:00 AM
Abstract :
Electron spin resonance investigations at 9.24 GHz in Si-doped two-line ferrihydrite (Si/FeOOH·nH2O) nanoparticles of size ≃4 nm are reported for x=Si/(Si+Fe)=0, 0.02, 0.05, 0.10 and 0.15. For all samples, a single broad resonance near g≃2 is observed; however with increase in x, both the resonance field Hr and linewidth ΔH increase but integrated intensity I of the line decreases, similar to the observed decrease in magnetization with x. These observations suggest that the observed resonance is due to uncompensated Fe3+ surface spins. Temperature variation (300 K to 80 K) of Hr and ΔH for x=0.05 shows a downward shift (δHr) of the line with a rapid increase in ΔH so that δHr∝(ΔH)3 predicted for randomly oriented nanoparticles is observed
Keywords :
iron compounds; magnetic particles; magnetisation; nanostructured materials; paramagnetic resonance; silicon; 4 nm; 9.24 GHz; FeOOH(H2O):Si; Si doping; Si/FeOOH·nH2O; electron spin resonance properties; ferrihydrite nanoparticles; linewidth; resonance field; single broad resonance; uncompensated Fe3+ surface spins; Doping; Electromagnetic wave absorption; Iron; Magnetic resonance; Magnetic separation; Nanoparticles; Paramagnetic resonance; Temperature; X-ray diffraction; X-ray scattering;
Journal_Title :
Magnetics, IEEE Transactions on
