Interparticle interaction and size effect in polymer coated magnetite nanoparticles

Abstract

Magnetization and Mössbauer studies have been performed on the polymer coated magnetite nanoparticles with particle size from 5.1 to 14.7 nm. The maximum in the temperature dependence of magnetization (T M ) is found to be inconsistent with the particle size (D TEM ). The effective magnetic anisotropy (K an ) is found to increase with the decrease of D TEM , which is attributed to the increase of surface anisotropy. The absence of coercivity and remanence of magnetization noticed well above T M indicates the superparamagnetic behaviour, which has also been observed in the temperature dependent Mössbauer results. The temperature dependence of hyperfine field is found to follow similar dependence of saturation magnetization for bulk magnetite.

Size effects and interactions in La0.7Ca0.3MnO3 nanoparticles

“…9 (solid curve). As seen in Table 2, the values of M S (0) and B increase as particle size increases, while the value of ε decreases and it is close with the value of ε = 3/2 of bulk materials [29].…”

“…Eq. (7) is known as the Bloch T 3/2 law with ε = 3/2 which has been verified experimentally for most of the bulk materials [29]. However, in nanoparticles, the thermal dependence of magnetization deviates from the expected Bloch law as the magnons with wavelength larger than the particle diameter cannot be excited and a threshold of thermal energy is required to generate spin waves [7,30].…”

Characterization of magnetite nanoparticles supported in sulfonated styrene-divinylbenzene mesoporous copolymer

“…Data points are better described for the curve corresponding to ε = 2, which is in good agreement with results reported for magnetite nanoparticles. Values of B 0 ∼ 6.5-7.0 × 10 −7 K −2 were determined from our data, suggesting that the value of J remains essentially the same as in bulk magnetite [14]. Zero field-cooled (ZFC) and field-cooled (FC) curves of sample 6C2M are presented in Fig.…”

“…The hyperfine fields for both iron ion sites show a monotonic reduction as the temperature is increased. Considering the relationship between the hyperfine field (B hf ) and the saturation magnetization (M S ), B hf (T) ∝ M S (T), and taking into account that in the thermodynamic equilibrium the low energy collective excitations (spin waves) result in the decrease of the spontaneous magnetization as the temperature increases, the hyperfine field is expected to follow the relation [14]:…”

Thermo-sensitive Electrospun Fibrous Magnetic Composite Sheets

“…These magnetic materials can be tailored with the various shapes such as particles, rod, wire, and their composites to improve the magnetic properties and biocompatibility [5][6][7][8]. In general, the magnetic thermo-sensitive materials especially, MNPs and their colloids have been widely studied in local hyperthermia [1][2][3][4][5][6][7][8]. To apply the hyperthermia of MNPs, it should evenly disperse throughout the fluid.…”