Magnetic phases of imperfectly crystalline Co2SiO4

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 Co2SiO4. The study also deals with the magnetic parameters of the composites Co2O3±SiO2, 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 di€raction (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 Co2SiO4 is shown to have uniaxial anisotropy, detected by magnetization versus ®eld curves. Ó 2000 Published by Elsevier Science B.V. All rights reserved.