One-Pot Synthesis of Highly Monodispersed Ferrite Nanocrystals: Surface Characterization and Magnetic Properties

Abstract

In the present study, a facile one-pot synthetic route, utilizing a strong polar organic solvent, N-methyl 2-pyrrolidone (NMP), is demonstrated to obtain highly monodispersed ferrite nanocrystals. The equimolar mixture of oleic acid, C(17)H(33)COOH (R-COOH), and oleylamine, C(18)H(35)NH(2) (R'-NH(2)), was used to coat the magnetic nanocrystals. Structural and magnetic properties of the ferrite nanocrystals were studied by a multitechnique approach including X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM), and Mössbauer spectroscopy. FTIR spectral analysis indicates oleylamine helps in deprotonation of oleic acid, resulting in the formation of an acid-base complex, R-COO¯:NH(3)(+)-R', which acts as binary capping agent. Structural and coordination differences of iron were studied by XPS and Mössbauer spectral analysis. XPS analysis was carried out to examine the oxidation state of iron ions in iron oxide nanocrystals. The presence of a magnetically dead layer (∼0.38 and ∼0.67 nm) and a nonmagnetic organic coating (∼2.3 and ∼1.7 nm) may substantially reduce the saturation magnetization values for CoFe(2)O(4) and Fe(3)O(4) nanocrystals, respectively. The energy barrier distribution function of magnetic anisotropy was derived from the temperature dependent decay of magnetization. A very narrow energy barrier distribution elucidates that the ferrite nanocrystals obtained in this study are highly monodispersed.

Magnetic and Impedance Properties of Nanocomposite CoFe2O4/Co0.7Fe0.3 and Single‐Phase CoFe2O4 Prepared Via a One‐Step Hydrothermal Synthesis

“…However, in our synthesized samples, cation distribution or off‐stoichiometry is not suggested to be the main reason for the highest magnetization of sample A. The M s value of single crystal CFO, synthesized by solid‐state reaction, only reaches 90 emu/g, at 5 K . However, the M FC value of sample A reached 91 emu/g at 200 K, which is even higher than that value.…”

“…Figure shows the temperature dependence of magnetization M ( T ) with zero‐field cooling (ZFC) and field cooling (FC) at H = 1 T. For sample A, at 164 K, the ZFC magnetization ( M ZFC ) value was beyond the measuring range of the SQUID, because of the large magnetization, while M ZFC around 200 K reached 91.4 emu/g, exceeding the 90 emu/g (at 5 K) of single crystal CoFe 2 O 4 . For samples C and E, the FC magnetization ( M FC ) at low temperature remains almost constant, indicating the presence of dipolar interactions …”

“…T irr is related to the blocking temperature of the largest particles. It is defined as the temperature at which the difference between M FC and M ZFC , normalized to its maximum value M FC at T min = 200 K for sample A and at T min = 10 K for samples C and E, is equal to 1%, i.e., , as shown in Fig. .…”

Effect of sequential morphology adjustment of hematite nanoplates to nanospindles on their properties and applications

“…1a match well with JCPDS card no. 17,18 The peak at 1384 cm À1 shows the presence of NO 3 À . As shown in Fig.…”

The stress, surface spin and dipolar interaction in the diluted NiFe 2 O 4 nanoparticles by the SiO 2 matrix: Characterization and analyses

“…Furthermore it can be noted in the case of the NFH sample that the ZFC peak is broader; this mainly results from two factors: the particle size distribution or interparticle interactions [9], but taking into account the same particle size distribution in all of samples, the dipolar interaction is suggested to be responsible for the ZFC peak broadening. Again the nature of FC curve, which gradually decreases with increasing temperature, rules out the presence of strong dipolar interactions in the case of NFL, while, in the case of NFH sample, almost constant value of FC curve below T B is an indication for the presence of dipolar interactions [22]. In a word, the strong dipolar interaction increases the T B value and broadens the ZFC peak; above T B , the ZFC and FC curves overlap and the superparamagnetism has usually been suggested to present in samples [1,9].…”