Role of the rare-earth on the electrical and magnetic properties of cobaltperovskites

The magnetic and electrical properties of R1-xSrxCoO3 materials (R=La, Pr, Nd, Gd) (0 less than or equal to x less than or equal to 0.50) are studied. Rare-earths with angular momentum L not equal 0 enhance coercive field val ues. They are maximum for R = Nd (the highest L) and much smaller for Gd an d La (L = 0). The result is interpreted as the contribution of the L-S coup ling in the rare-earth to the magnetic anisotropy of the system. Electrical conductivity is improved with Sr doping, but increases of rare-earth atomi c number lead to decreases of conductivity. This is attributed to the incre ase of lattice distortions, due to the smaller R3+ ionic size, and to the e ffect of the rare-earth on the spin state of cobalt ions. (C) 2000 American Institute of Physics. [S0021-8979(00)92608-2].