Date of Graduation

2000

Document Type

Thesis

Degree Type

MS

Committee Chair

M. S. Seehra

Abstract

The magnetic properties of nanosized (3-5nm) Si-doped two line ferrihydrites, Six /FeOOH.nH2 O where x = 0, 0.02, 0.05, 0.1, 0.15, 0.20, 0.26, 0.40, 0.50 have been investigated here. The experiments conducted include temperature(5K – 300K) and magnetic field(upto 55 kOe) variations of magnetization under zero field cooled and field cooled conditions. The quantities determined are the magnetic moment per particle mp , the temperature Tp (m) at which magnetization peaks, the spin glass order transition temperature Tg and the hysteresis loop parameters (coercivity Hc , remanence Mr and saturation magnetization Ms (H ® 0)). The dramatic changes observed in the parameters for x > 0.20 leads to the model in which Si replaces the uncompensated surface spins preferentially for initial dopings and for x > 0.20, magnetic dilution of the sites in the antiferromagnetic nanoparticle core starts to occur.

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