Magnetic phases of imperfectly crystalline Co2SiO4

Abstract

Systems consisting of magnetic particles embedded in a silica matrix have been used in magnetic recording, their study being thus an actual theme of research. In this work, we report some of the main results of a systematic study conducted to determine properties of the magnetic phases of the system Co 2 SiO 4 . The study also deals with the magnetic parameters of the composites Co 2 O 3 ±SiO 2 , in an attempt to establish relationships between structural environment and the magnetic properties. Polycrystalline sintered samples were prepared using a chemical route, structurally and magnetically measured using X-ray diraction (XRD), electron microscopy and magnetometry. For applied magnetic ®elds of the order of tens of Oersteds, the system has ferromagnetic (F) order, whereas for ®elds of a few thousands of Oersteds, a frustated antiferromagnetic (AF) response is detected. Our measurements detect the existence of ferromagnetic and antiferromagnetic interactions. Also, crystalline Co 2 SiO 4 is shown to have uniaxial anisotropy, detected by magnetization versus ®eld curves. Ó

Direct synthesis of mesoporous silica containing cobalt: A new strategy using a cobalt soap as a co-template

“…This could correspond to the formation of cobalt silicate clusters like olivine Co 2 SiO 4 which is known to behave as a frustrated antiferromagnet. It may exhibit ferromagnetism when imperfectly crystallized but contains only metal centres in octahedral sites [34,35]. A similar ferromagnetic-like behavior was also reported for Co 2 O 3 particles in silica matrix [35].…”

“…It may exhibit ferromagnetism when imperfectly crystallized but contains only metal centres in octahedral sites [34,35]. A similar ferromagnetic-like behavior was also reported for Co 2 O 3 particles in silica matrix [35].…”

Hard magnetism in structurally engineered silica nanocomposite

“…The appearance of Co 2 SiO 4 at 700 1C is noteworthy, as the temperature is higher than 700 1C in other examples of Co 2 SiO 4 formation, 31,32 and sometimes over 1000 1C. 28 In this study, Fe ions are thought to affect the early formation of Co 2 SiO 4 .…”

Binary CoOx–SiO2 Porous Nanostructures for Catalytic CO Oxidation

“…Unfortunately, both XRD and TEM/TED investigations were unsuccessful (no Bragg peaks detected) for the MUB-100(2) and MUB-100(1) materials. Considering the pale blue color of the MUB-100(1) monolith (Figure 1b), we first intuited that the phase present was amorphous Co 2 SiO 4 , 38 but this phase is normally appearing only above 1100 °C when addressing acidic based syntheses, 38 while the thermal treatment applied here is reaching a maximum temperature of 700 °C. To get the spinel Co 2 SiO 4 at relatively low temperature, the synthetic path should be addressed under alkaline conditions (above the silica isoelectric point) where the Co 2+ species will have molecular affinity with the negatively charged silicate precursors.…”