ESR studies of magnetic clusters in Li Ni O 1yx 1qx 2

A brief account is given of the resolution of Bloch’s equation in order to have access to the frequency of precession of the magnetisation of a paramagnetic system or a ferromagnetic one with axial symmetry. These results are used to understand the magnetic properties of several compounds of the Li1yx Ni1qxO2 family with xs0.02, 0.07 and 0.14, using electron spin resonance measurements. The compound with xs0.02 is shown to have a paramagnetic behaviour, while the compound with xs0.14 orders ferromagnetically below 150 K. Both types of behaviour are observed in the compound with xs0.07. These results are discussed in terms of magnetic cluster formation in these compounds. q2000 Elsevier Science B.V. All rights reserved.