Magnetic and electrical transport properties of La0.5A0.5CoO3 nanoparticles (A = Sr, Ca, and Ba)

We have investigated the effect of particle size on the electrical transport and magnetic properties of La0.5A0.5CoO3 (A = Sr, Ca, and Ba) nanoparticles synthesized by sol–gel technique. A size-induced metal to insulator transition is observed in the resistivity behaviour of Sr- and Ba-doped samples as the dimension changes from higher to lower ones. The magnetoresistance exhibits almost linear behaviour throughout the studied field range. The zero-field-cooled (ZFC) and field-cooled (FC) magnetizations display a broad paramagnetic to ferromagnetic transition at TC with a large magnetic irreversibility. The magnetization results indicate that Co3+ ions are in the intermediate spin state but Co4+ ions stay in a mixture of intermediate and high spin states. The observed frequency dependent shoulder in the in-phase and the peak in the out of phase component of the ac susceptibility indicate the glassy nature of the samples. The analysis of the ac magnetization results suggests that the magnetic behaviour is consistent with the cluster glass model.

Research highlights► La0.5A0.5CoO3 (A = Sr, Ca, and Ba) nanoparticles prepared by sol–gel technique. ► Size-induced metal–insulator transition in Sr- and Ba-doped samples. ► Broad paramagnetic to ferromagnetic transition with large magnetic irreversibility. ► Co3+ ions in intermediate and Co4+ in a mixture of intermediate and high spin states. ► ac magnetization suggests magnetic cluster glass nature of the samples.