The M?ssbauer spectra of 80 ? magnetite particles before and after coating with the three different organic surfactants were measured. The M?ssbauer spectra after coating appear as dispersion to a different degree with the different organism. When magnetic field (8 kOe) was applied, the superparamagnetic spectra for all sample disappeared and the spectra appeared as sextets. The experimental results showed that the organism produce pinning of the spin of the iron ions on the magnetite particle surface. The depth of pinning with and without applied magnetic field were calculated.