مشخصات پژوهش

عنوان	The effect of the magnetically dead layer on the magnetization and the magnetic anisotropy of the dextran coated magnetite nanoparticles
نوع پژوهش	مقاله چاپ‌شده
کلیدواژه‌ها	Effective magnetic anisotropy, Dipolar interactions, Magnetic dead layer, Core–shell model, Spin disorder, Surface magnetic anisotropy, Dextran-coated magnetite NPs
چکیده	We present a study on the magnetic behavior of dextran-coated magnetite nanoparticles (DM NPs) with sizes between 3 and 19 nm, synthesized by hydrothermal-assisted co-precipitation method. The decrease of saturation magnetization (Ms) with decreasing particle size has been modeled by assuming the existence of a spin-disordered layer at the particle surface, which is magnetically dead. Based on this core–shell model and taking into account the weight contribution of non-magnetic coating layer (dextran) to the whole magnetization, the dead layer thickness (t) and saturation magnetization Ms of the magnetic cores in our samples were estimated to be t = 6.8 Å and Ms = 98.8 emu∕g, respectively. The data of Ms were analyzed using a law of approach to saturation, indicating an increase in effective magnetic anisotropy (Keff) with decreasing the particle size as expected from the increased surface/volume ratio in small MNPs. The obtained Keff values were successfully modeled by including an extra contribution of dipolar interactions due to the formation of chain-like clusters of MNPs. The surface magnetic anisotropy (Ks) was estimated to be about Ks = 1.04 ×105J∕m3. Our method provides a simple and accurate way to obtain the M s core values in surface-disordered MNPs, a relevant parameter required for magnetic modeling in many applications
پژوهشگران	گراردو گویا (نفر سوم)، میثم سلیمانی (نفر چهارم)، غلامرضا نبیونی (نفر دوم)، ژیلا شاطر آبادی (نفر اول)