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Structure and magnetism of transition metal-based nanoparticles
Mantlíková, Alice
The aim of the work is characterization of structure and magnetic properties of various CoFe2O4/SiO2 nanocomposites. Emphasis was put on the corelation of the magnetic properties with particle size (samples with different annealing temperature) and with strenght of the interparticle interactions (samples with different Fe/Si ratio or without silica matrix). Structure properties of all samples were determinated by powder x-ray diffraction, scanning and transmission electron microscopy. Magnetic properties were determinated by standard (temperature dependence of magnetization, magnetization isotherms) and advanced (a.c. susceptibility, memory effects) magnetic measurements. A sharp increase of the values of blocking temperature and coercivity with increase of strenght of the interparticle interactions and with increase of particle size was observed. Particle size determines the maximum value of coercivity and blocking temperature and strengh of the interparticle interactions shift this values in the interval determined by particle size.
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Structure and magnetism of transition metal-based nanoparticles
Mantlíková, Alice
The aim of the work is characterization of structure and magnetic properties of various CoFe2O4/SiO2 nanocomposites. Emphasis was put on the corelation of the magnetic properties with particle size (samples with different annealing temperature) and with strenght of the interparticle interactions (samples with different Fe/Si ratio or without silica matrix). Structure properties of all samples were determinated by powder x-ray diffraction, scanning and transmission electron microscopy. Magnetic properties were determinated by standard (temperature dependence of magnetization, magnetization isotherms) and advanced (a.c. susceptibility, memory effects) magnetic measurements. A sharp increase of the values of blocking temperature and coercivity with increase of strenght of the interparticle interactions and with increase of particle size was observed. Particle size determines the maximum value of coercivity and blocking temperature and strengh of the interparticle interactions shift this values in the interval determined by particle size.
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Structure and magnetism of transition metal-based nanoparticles
Mantlíková, Alice ; Kalbáčová Vejpravová, Jana (advisor) ; Prchal, Jiří (referee)
The aim of the work is characterization of structure and magnetic properties of various CoFe2O4/SiO2 nanocomposites. Emphasis was put on the corelation of the magnetic properties with particle size (samples with different annealing temperature) and with strenght of the interparticle interactions (samples with different Fe/Si ratio or without silica matrix). Structure properties of all samples were determinated by powder x-ray diffraction, scanning and transmission electron microscopy. Magnetic properties were determinated by standard (temperature dependence of magnetization, magnetization isotherms) and advanced (a.c. susceptibility, memory effects) magnetic measurements. A sharp increase of the values of blocking temperature and coercivity with increase of strenght of the interparticle interactions and with increase of particle size was observed. Particle size determines the maximum value of coercivity and blocking temperature and strengh of the interparticle interactions shift this values in the interval determined by particle size.
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Magnetic properties of doped CeO.sub.2./sub. nanoparticles and CeO.sub.2./sub.-Fe.sub.2./sub.O.sub.3./sub. mixed oxides
Mantlíková, Alice ; Bittová, Barbara ; Burianová, Simona ; Vejpravová, Jana ; Nižňanský, D. ; Holec, Petr
We have investigated magnetic properties of CeO2 nanoparticles and CeO2/SiO2 nanocomposites doped by various magnetic metal oxide ions (Fe, Gd, Sm, Nd). Samples were obtained by co-precipitation and sol-gel method. Particle size has been obtained as 5 - 25 nm for nanocomposite and 25 - 100 nm for nanoparticles increasing with the increase of the annealing temperature. Detailed measurements of magnetization demonstrate paramagnetic state in the majority of the doped samples with maximum magnetization decreasing with the decrease of effective magnetic moment of the dopant ions from Gd3+ to Nd3+. It has been also observed, that the high-coercivity ε-Fe2O3 forms in CeO2-Fe2O3/SiO2 nanocomposite for higher concentration of the Fe ions (Ce/Fe/Si ratio equal to 1/2/9) and for the highest annealing temperature.
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