NiFe2O4 nanoparticles in
ferrofluids: evidence of spin disorder in the surface layer
M.H. Sousa, E. Hasmonay, J. Depeyrot, F.A. Tourinho,
J.-C. Bacri,
E. Dubois, R. Perzynski, Yu.L. Raikher
We show that surface magnetic properties of NiFe2O4 nanoparticles constituting ionic ferrofluids can
be investigated in macroscopic experiments. Cross-analysis of static
magnetization and field-induced birefringence prove that the particles consist
of a uniformly magnetized core and a spin-disordered surface layer of
comparable thickness.
Keywords:
Nanoparticles; Nickel ferrite; Magnetic fluids; Magnetic birefringence