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 envi-ronment and the magnetic properties. Polycrystalline sintered samples were prepared using a chemical route, struc-turally and magnetically measured using X-ray diraction (XRD), electron microscopy and magnetometry. For applied magnetic fields of the order of tens of Oersteds, the system has ferromagnetic (F) order, whereas for fields 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 field curves. Ó 2000 Published by Elsevier Science B.V. All rights reserved. 1