ABSTRACT
Structure, characterization, and magnetic properties of Ti-doped LaFeO3 (LaFe(1-x)Ti(x)O3, x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) nanoparticles synthesized by polymerized complex method are investigated. All LaFe(1-x)Ti(x)O3 nanoparticles were successfully obtained from calcination of the precursor at 1050 degrees C in air for 2 h. The calcined LaFe(1-x)Ti(x)O3 samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge spectroscopy (XANES) and vibrating sample magnetometry (VSM). The XRD and TEM results showed that all LaFe(1-x)Ti(x)O3 samples had a single phase nature with the orthorhombic structure. The valence states were mixed in the Fe3+ and Fe4+ state for Fe ions and Ti4+ state for Ti ions, as confirmed by XPS and XANES results. The weak ferromagnetic behavior with the highest magnetization (M) of -0.23 emu/g at 10 kOe was obtained for x = 0.4. The origin of the ferromagnetism (FM) for all LaFe1-x)Ti(x)O3 samples supports the magnetic coupling between Fe3+ and Fe4+ ions via double exchange (DE) interaction.
ABSTRACT
Ferromagnetism was observed at room temperature in monodisperse CeO2 nanospheres synthesized by hydrothermal treatment of Ce(NO3)3·6H2O using polyvinylpyrrolidone as a surfactant. The structure and morphology of the products were characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and field-emission scanning electron microscopy (FE-SEM). The optical properties of the nanospheres were determined using UV and visible spectroscopy and photoluminescence (PL). The valence states of Ce ions were also determined using X-ray absorption near edge spectroscopy. The XRD results indicated that the synthesized samples had a cubic structure with a crystallite size in the range of approximately 9 to 19 nm. FE-SEM micrographs showed that the samples had a spherical morphology with a particle size in the range of approximately 100 to 250 nm. The samples also showed a strong UV absorption and room temperature PL. The emission might be due to charge transfer transitions from the 4f band to the valence band of the oxide. The magnetic properties of the samples were studied using a vibrating sample magnetometer. The samples exhibited room temperature ferromagnetism with a small magnetization of approximately 0.0026 to 0.016 emu/g at 10 kOe. Our results indicate that oxygen vacancies could be involved in the ferromagnetic exchange, and the possible mechanism of formation was discussed based on the experimental results.
ABSTRACT
RT ferromagnetism was observed in nanoparticles of Fe-doped CeO2 (i.e., Ce(0.97)Fe(0.03)O2) synthesized by a sol-gel method. The undoped and Fe-doped CeO2 were characterized by XRD, Raman spectroscopy, TEM, and VSM. The undoped samples and Ce(0.97)Fe(0.03)O2 precursor exhibit a diamagnetic behavior. The 673 K-calcined Ce(0.97)Fe(0.03)O2 sample is paramagnetic whereas 773 and 873 K-calcined Ce(0.97)Fe(0.03)O2 samples are ferromagnetism having the magnetizations of 4.65 x 10(-3) emu/g and 6.20 x 10(-3) emu/g at 10 kOe, respectively. Our results indicate that the ferromagnetic property is intrinsic to the Fe-doped CeO2 system and is not a result of any secondary magnetic phase or cluster formation.
