Coercivity of homogenized ensembles of anisotropic γ-Fe2O3 nanoparticles

Strain-induced macroscopic magnetic anisotropy from smectic liquid-crystalline elastomer–maghemite nanoparticle hybrid nanocomposites

“…This again proves both, that the particles are well dispersed and do not interact, and that the composition of the ferrimagnetic particles does not change with increasing loading, which is also supported by the normalized hysteresis loops. [55][56][57] There is also a signicant anisotropy of the coercive eld. In theory, independent of the population of particles at an orientation angle q, any non-zero population value should generate an identical coercive eld in the direction of the shape-anisotropic particle orientation, according to the Stoner-Wohlfarth theory.…”

Effect of contacts between γ-Fe2O3 nanoparticles on their phase-transition temperature

“…In addition, the previous history of γ Fe 2 O 3 nanoparticles, which is associated with the formation of the γ phase during high temperature oxi dation of Fe 3 O 4 particles, may also affect the tempera ture of their transition to the α phase (see, for exam ple, [4]). However, first, the oxidation temperature for nanoparticles normally does not exceed 300°C (i.e., the temperature range in which the M S (T)/M 0 depen dences are reversible for all specimens investigated here).…”

“…3, γ Fe 2 O 3 particles were com pacted to an apparent density of about 1 g/cm 3 . For this purpose, the water-alcohol suspension of γ Fe 2 O 3 particles was also first homogenized and filtered through the membrane filter in accordance with the procedure described in [4]. Then, this filtered suspen sion of γ Fe 2 O 3 particles was placed into a gradient magnetic field (~8 × 10 3 G/cm) and deposited under the periodic action of ultrasound.…”

“…van der Waals con tacts for one domain magnetic nanoparticles are enhanced by magnetic interactions. As a result, their one domain state is noticeably perturbed, which is manifested in magnetic properties [4] (in particular, in the coercive force and residual magnetization). The technology of preparing uniformly homogenized ensembles of magnetic nanoparticles developed in [4] paved the way for studying a number of new phenom ena associated with the effect of contacts between nanoparticles and, accordingly, for searching methods for stabilizing their properties.…”

“…For this purpose, the rated amount of liquid glass (Na 2 SiO 3 ) sufficient for the for mation of two SiO 2 monolayers on the surface of par ticles was added to the aqueous suspension of parti cles. Then, the suspension was homogenized and fil tered through a membrane filter according to the technique described in [4]. The filtered suspension was pulverized by ultrasound and used after sublimation drying for preparing uniformly homogenized samples.…”