کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
8156140 | 1524844 | 2015 | 8 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Size and surface effects in the magnetic order of CoFe2O4 nanoparticles
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
فیزیک و نجوم
فیزیک ماده چگال
پیش نمایش صفحه اول مقاله
![عکس صفحه اول مقاله: Size and surface effects in the magnetic order of CoFe2O4 nanoparticles Size and surface effects in the magnetic order of CoFe2O4 nanoparticles](/preview/png/8156140.png)
چکیده انگلیسی
In this work, we have focused on the size dependence of the magnetic properties and the surface effects of CoFe2O4 nanoparticles synthesized by high-temperature chemical method with diameter d~2, 4.5, and 7Â nm, with narrow size distribution. transmission electron microscopy (TEM) images and X-ray diffraction (XRD) profiles indicates that samples with 7 and 4.5Â nm present a high crystallinity while the 2Â nm sample has a poor one. We have investigated by magnetization measurements and in-field Mössbauer spectroscopy the influence of the surface in the internal magnetic order of the particles. Particles with d=7Â nm have almost single domain behavior and the monodomain occupies approximately the whole particle. In the sample with d=4.5Â nm the surface anisotropy is large enough to alter the ferrimagnetic order in the particle shell. Then, a surface/volume ratio of ~60% is the crossover between a single domain nanoparticle and a frustrated order in a magnetic core-shell structure, due to the competition between surface anisotropy and exchange interaction+crystalline anisotropy in cobalt ferrite. In the d=2Â nm sample the poor crystallinity and the large surface/volume ratio avoid the ferrimagnetic order in the particle down to T=5Â K.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Magnetism and Magnetic Materials - Volume 377, 1 March 2015, Pages 44-51
Journal: Journal of Magnetism and Magnetic Materials - Volume 377, 1 March 2015, Pages 44-51
نویسندگان
Betiana N. Pianciola, Enio Jr., Horacio E. Troiani, Luiz C.C.M. Nagamine, R. Cohen, Roberto D. Zysler,