Publicación:
Suppression of exchange bias effect in maghemite nanoparticles functionalized with H2Y
Suppression of exchange bias effect in maghemite nanoparticles functionalized with H2Y
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Fecha
2016
Autores
Guivar J.A.R.
Morales M.A.
Litterst F.J.
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Elsevier
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Abstracto
The structural, vibrational, morphological and magnetic properties of maghemite (γ-Fe2O3)
nanoparticles functionalized with polar molecules EDTA(or H4Y) and H2Y are reported. The samples
were functionalized before and after total synthesis of γ-Fe2O3 nanoparticles. The molecules are anchored
on the monodentate mode on the nanoparticles surface. Transmission electron microscopy (TEM)
revealed the formation of maghemite nanoparticles with small diameter of 4 nm for the sample
functionalized upon synthesis and 7.6 and 6.9 nm for the samples functionalized with EDTA and H2Y
after the formation of nanoparticles. Exchange bias phenomena were observed in some of the samples
functionalized with EDTA at temperatures below 70 K. The presence of the bias effect was discussed in
terms of the formation of a thin layer of a secondary phase like lepidocrocite, and the absence of this
effect was explained in terms of the chemisorption of carboxylic groups from EDTA which suppressed
the canting. Studies of Mössbauer spectroscopy as a function of temperature showed slow relaxation
effects and allowed discussion of the secondary phase. In the M-T curves a maximum around 116 K was
associated with this secondary phase also in agreement with the Mössbauer studies. The dynamic
properties were studied by AC susceptibility, the out of phase signal revealed a spin glass like regime
below 36.5 K.
Descripción
Palabras clave
Transmission electron microscopy,
Ethylenediaminetetraacetic acid,
High resolution transmission electron microscopy,
Magnetic susceptibility,
Molecules,
Nanomagnetics,
Nanoparticles,
Spin glass,
Spin glass,
Ac susceptibility,
Dynamic property