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Magnetic clusters formation in Li_{1-x}Ni_{1+x}O_2 compounds : experiments and numerical simulations

D. Mertz·Y. Ksari·F. Celestini·J. M. Debierre·A. Stepanov·C. Delmas
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Abstract

The magnetic properties of Li_{1-x}Ni_{1+x}O_2 compounds with x ranging between 0.02 and 0.2 are investigated. Magnetization and ac susceptibility measured at temperatures between 2 K and 300 K reveal a high sensitivity to x, the excess Nickel concentration. We introduce a percolation model describing the formation of Ni clusters and use an Ising model to simulate their magnetic properties. Numerical results, obtained by a Monte-Carlo technique, are compared to the experimental data. We show the existence of a critical concentration, x_c = 0.136, locating the Ni percolation threshold. The system is superparamagnetic for x x_c. The 180 Ni-O-Ni inter-plane super-exchange coupling J_\perp \simeq -110K is confirmed to be the predominant magnetic interaction. From the low temperature behavior, we find a clear indication of a 90 Ni-O-Ni intra-plane antiferromagnetic interaction $J_\parallel \simeq -1.5K$ which implies magnetic frustration.

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D. Mertz, Y. Ksari, F. Celestini, J. M. Debierre, A. Stepanov, C. Delmas. 1999-04-14. Magnetic clusters formation in Li_{1-x}Ni_{1+x}O_2 compounds : experiments and numerical simulations. https://doi.org/10.1103/physrevb.61.1240

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