Nanopartículas de ferrita MFe₂O₄ (M = Ni y Zn): síntesis hidrotermal y propiedades magnéticas

Abstract

MFe 2 O 4 (M = Ni and Zn) nanoparticles were prepared by the hydrothermal method. The obtained samples were characterized by X-ray and electron diffraction, Scanning and Transmission Electron Microscopy and Mössbauer spectroscopy. The transmission images show homogeneous shape and particle size ranging from 10 to 40 nm, depending on the nature of the M cation. Mössbauer spectroscopy yields to a ratio of occupancy between the A and B sites of 0.7 in the case of NiFe 2 O 4 oxide. DC magnetization (2-300 K) measurements reveal a superparamagnetic behaviour for the ZnFe 2 O 4 sample with a blocking temperature of 20 K. By contrast, in the case of the NiFe 2 O 4 ferrite the blocking temperature appears to be above 300 K and at lower temperature, it shows a ferrimagnetic behaviour arising from the superexchange interactions that take place in this inverse spinel. Mössbauer spectroscopy results confirm the bulk magnetic measurements.Keywords: ferrites, nanoparticles, superparamagnetism, ferrimagnetism, inverse spinel. Nanopartículas de ferrita MFe 2 O 4 (M = Ni y Zn): síntesis hidrotermal y propiedades magnéticas.Se han preparado mediante el método hidrotermal nanopartículas de ferritas MFe 2 O 4 (M = Ni, Zn). Las muestras obtenidas fueron caracterizadas mediante difracción de rayos X y electrones, microscopía electrónica de transmisión y barrido y espectroscopia Mössbauer. Las imágenes de transmisión muestran partículas de forma y tamaño homogéneo de 10 a 40 nm según la naturaleza del catión M. La espectroscopia Mössbauer revela una relación de ocupación entre los sitios A y B por los átomos de hierro de 0.7 en el caso del óxido NiFe 2 O 4 . Las medidas de magnetización DC (2 -300 K) muestran un comportamiento superparamagnético para la muestra ZnFe 2 O 4 con una temperatura de bloqueo de 20 K. En el caso de las nanopartículas de NiFe 2 O 4 la temperatura de bloqueo parece estar por encima de los 300 K mostrando por debajo de la misma, comportamiento ferrimagnético provocado por las interacciones de superintercambio que tienen lugar en esta espinela inversa. Los resultados de espectroscopia Mössbauer confirman los datos de las medidas magnéticas.Palabras clave: ferritas, nanopartículas, superparamgnetismo, ferrimagnetismo, espinela inversa.

Composition, Electronic and Magnetic Investigation of the Encapsulated ZnFe2O4 Nanoparticles in Multiwall Carbon Nanotubes Containing Ni Residuals

“…The higher observed T B at 270 K gives experimental evidence of the existence of another magnetic sub-system characteristic of Ni residuals in mCNTs. The ZFC trend is similar to that of the reported NiFe 2 O 4 nanoparticles of 40 nm size with T B  = 250 K [30]. Although the cooling curves seen in Fig.…”

“…The lower T B at ~22 K is the blocking temperature of ZnFe 2 O 4 nanoparticles—indicated by arrows in Fig. 7a, expressing the known behavior of the zinc ferrite nanoparticles of ~10 nm size [30, 31]. To verify the above observation, magnetization versus temperature measurement was acquired at a higher applied field, 5000 Oe, see Fig.…”

Superparamagnetism and interparticle interactions in ZnFe2O4 nanocrystals

“…The solvothermal method was used to obtain the nanosized particles. 12,19,20 Stoichiometric amounts of iron and zinc nitrates were dissolved in ethylene glycol, water or glycerol in a 10 À5 or 10 À4 mol mL À1 concentration and the corresponding hydroxides were precipitated with KOH (pH ¼ 11). Afterwards, the obtained brown mixture was transferred into a stainless steel autoclave to be solvothermally treated.…”

“…13 Nowadays nanochemistry is focused on obtaining particles with homogeneous size and shape, and there are several experimental techniques that can be employed for such a purpose: co-precipitation, 14 mechanosynthesis, 15,16 sol-gel, 9 thermal decomposition 17 or microemulsion. 18 Among these kinds of synthesis, the solvothermal method 19,20 has been found to be one of the most useful due to its simplicity and low cost conditions and reactants. Furthermore, it offers the possibility to deal with a great number of experimental strategies by modification of some experimental parameters such as solvent, precipitant agent concentration or temperature.…”

A simple solvothermal synthesis of MFe2O4 (M=Mn, Co and Ni) nanoparticles

“…Techniques such as sol-gel [30], coprecipitation [31], [32] and [33], mechanochemical processing [34] and [35], microemulsion [26], [36] and [37] and microwaves [38] have been commonly used to prepare ferrite nanoparticles. But, until now, the most economical ways for the production of large quantities of nanosized ferrite particles are chemical precipitation [39] and solvothermal synthesis [11], [19], [40], [41] and [42]. In general, solvothermal synthesis offers many advantages over other methods, such as its simplicity, the high crystallinity of the obtained products at relatively low temperature (T~180 °C), the capability to control crystal growth and its adequacy for the preparation of large quantities of samples.…”