http://files.janapv.webnode.cz/200000097-8a03f8afdf/ex_bias_nano.pdf

Exchange bias in nanostructures

Magnetic Relaxation in Fine‐Particle Systems

https://dyuthi.cusat.ac.in/xmlui/bitstream/handle/purl/4347/Finite%20size%20effects%20on%20the%20structural%20and%20magnetic%20properties%20of%20sol%e2%80%93gel%20synthesized%20NiFe2O4%20powders.pdf?sequence=1

Finite size effects on the structural and magnetic properties of sol–gel synthesized NiFe2O4 powders

Nanostructured CoFe2O4 particles were prepared by a sonochemical approach, first by preparation of the amorphous precursor powders, followed by heat treatment at relatively very low temperatures. The precursor was prepared by sonochemical decomposition of solutions of volatile organic precursors, Fe(CO)5 and Co(NO)(CO)3, in Decalin at 273 K, under an oxygen pressure of 100−150 kPa. The amorphous nature of these particles was confirmed by various techniques, such as scanning and transmission electron microscopy (SEM and TEM), electron microdiffraction, and X-ray diffractograms. Magnetic measurements, Mossbauer, and electron paramagnetic resonance (EPR) spectral studies indicated that the as-prepared amorphous particles were superparamagnetic. The Mossbauer parameters and the significantly low (45 emu/g) observed saturation of magnetization of the annealed sample, compared to that of the bulk sample (72 emu/g), reflected its nanocrystalline nature.

/pdf/sonochemical-preparation-and-size-dependent-properties-of-26w3kywyvc.pdf

Sonochemical Preparation and Size-Dependent Properties of Nanostructured CoFe2O4 Particles

The effect of surface inorganic−organic interactions on magnetic and structural properties of iron oxide magnetic nanoparticles functionalized by lipophilic stilbene molecules has been investigated. The molecules have been grafted through either phosphonate or carboxylate coupling agents. Mossbauer spectra recorded at 300 and 77K suggest a global composition of Fe2.82O4 for the two types of functionalization. Complementary in-field Mossbauer and SQUID measurements have demonstrated that the nanoparticles consist in a magnetite core surrounded by an oxidized layer. The oxidized shell exhibits a spin canting in the carboxylate case leading to a decrease of the net magnetization of the oxide nanoparticle. No canting occurs in the phosphonate case, and the magnetic properties are therefore preserved. The magnetic properties thus depend on the coupling agent, e.g., surface interactions. This result is of primary importance to tune the magnetic properties of functionalized nanoparticles for biomedical and high ...

Coupling Agent Effect on Magnetic Properties of Functionalized Magnetite-Based Nanoparticles

The magnetic structure of small NiFe2O4 particles has been investigated. Samples (in the few hundred angstrom size range and up) were prepared by chemical precipitation followed by a heat treatment at relatively low temperatures. Mossbauer spectra of the 57Fe nuclei, obtained with a longitudinal magnetic field applied, unambiguously establish that a non‐collinear structure exists. Further, the magnetic moment at low temperatures is appreciably lower than the value reported for bulk material. A model is proposed in which the NiFe2O4 particles consist of a core with the usual spin arrangement and a surface layer with atomic moments inclined to the direction of the net magnetization. The temperature dependence of this structure is also reported.

K. Haneda

Papers

Magnetic structure of small NiFe2O4 particles