Magnetocaloric effect and size‐dependent study of the magnetic properties of cobalt ferrite nanoparticles prepared by solvothermal synthesis

Abstract

Cobalt ferrite (CoFe2O4) nanoparticles from 2 nm to 15 nm were synthesized using a solvothermal procedure. In this non‐aqueous method, acetophenone was used as solvent and the particle size was controlled by changing the reaction temperature from 120 °C to 180 ºC. Nanoparticles show good crystallinity and uniformity above 140 °C, as determined by X‐ray diffraction and transmission electron microscopy. Magnetic measurements indicate superparamagnetic behaviour. Zero‐field‐cooling (ZFC) dc‐magnetisation experiments at 100 Oe show blocking temperatures ranging from 215 K to more than 305 K. Saturation magnetisation increases with particle size and a small decrease is observed when increasing the temperature. The magnetocaloric effect shown by these cobalt ferrite nanoparticles is reasonably high for nanomaterials. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of Er doping on the structural and magnetic properties of cobalt-ferrite

“…information storage systems, 1 ferro-fluid technology, 2 magnetic refrigeration, 3 magnetic diagnostics, 4 and magnetostriction. 5 In cobalt-ferrite the presence of doping elements and the thermal history during the synthesis and processing alter the metal ions distribution and hence influence their structural and magnetic properties.…”

“…In region (ii)-all the compositions show two exothermic peaks around 300 C (DTA curve) corresponding to $50% weight loss. These peaks are probably due to the decomposition of complex gel network weight loss of gel network is due to the combustion reaction resulting in evolution of NH 3 and NO 2 corresponds to one of the peaks; and the other peak is likely associated with the burning of residual organic complex or oxidation of residual carbon in the gel network. In region (iii)-the peak at 535 C for CoFe 2 O 4 (DTA curve) shows no significant weight loss (TG curve) that can be attributed to crystallization.…”

Inverse magnetocaloric effect in sol–gel derived nanosized cobalt ferrite

“…Cobalt ferrite can be prepared in the nanoregime by cold precipitation techniques or sol-gel techniques. Cobalt ferrite, because of its large magnetocrystalline anisotropy, is expected to exhibit non-zero coercivity even at very small particle sizes of the order of 5 nm and is a promising candidate for many applications, namely magnetic data storage, magnetic drug targeting, biosensors, tumor treatment and magnetic refrigeration [19,20].…”

Synthesis and characterization of CoFe2O4–PVP nanocomposites

“…The particle size can be tailored by changing the treatment temperature: smaller particles (hD TEM i = 3.9 nm) and lager particles (hD TEM i = 6.6 nm) were obtained at 140 and 180°C, respectively [9]. In order to obtain stable dispersions, CoFe 2 O 4 nanoparticles were capped with dimercaptosuccinic acid (DMSA).…”

“…The solvothermal synthesis of CoFe 2 O 4 nanoparticles was previously reported [9]. In a typical synthesis, 0.5 mmol Co(III) acetylacetonate and 1 mmol Fe(III) acetylacetonate were dissolved directly in acetophenone under mild stirring for 30 min.…”