Magnetic Characterization of Bacterial Magnetic Particles

Mtissbauer measurement, chemical analysis (ratioof Fez+ to total Fe content), analyses ofthe rotational hysteresis loss (Wr) and the magnetic viscosity coefficient (Sv) for bacterial magnetic particles covered with organic thin films (BMPs) were investigated and compared with the results for Fes04 h e particles prepared by a chemical coprecipitation method. The calculated value of the saturation magnetization (Js) of BMPs was found to be 1.06 X 10.4 Wb mlkg (84.7 emulg) using Mtissbauer spectroscopy and chemical analysis. The WrIJs versus H curve for BMPs had a stronger peak than that of FesOe fine particles (Sample Cl). The rotational hysteresisintegrals (Rh) for BMPs andFes04 fine particles were 1.12 and 0.62, respectively: I t is believed that they have different magnetization reversalmechanisms. The Sv value of BMPs a t 127Alm was 50% smallerthan that of the Fes04fine particles (Cl). The diameter(Dact) of the activation volume (minimum volume for magnetization reversal) calculated from Sv, and the critical diameter (Dc) obtained by considering the superparamagnetic behavior for BMPs, were 39 and 22 nm, respectively. As the FesO4fine particles (Cl) have smallerDact(31 nm) andDc(18 nm), it may be concluded that BMPs is magnetically more stable than FeD4 fine particles (Cl).