Low-field magnetoresistance effect in core-shell structured La _0.7Sr _0.3CoO ₃ nanoparticles

Core-shell structured La _0.7Sr _0.3CoO ₃ nanoparticles are synthesized and their magnetic and magneto-transport properties are investigated. In these core-shell La _0.7Sr _0.3CoO ₃ nanoparticles, the cores are single-crystalline and ferromagnetic, whereas the shells are noncrystalline and predominantly paramagnetic. Moreover, the insulating-like shells can serve as a good spin tunneling barrier. Therefore, in such a special core-shell structure, the spin-polarized interparticle tunneling is improved due to the existence of shells, which thus induces an enhanced low-field magnetoresistance effect. Core-shell structured La _0.7Sr _0.3CoO ₃ nanoparticles are synthesized for the first time. The natural noncrystalline shell serves as a good spin-polarized tunneling barrier. Such a structure provides an effective approach for improvement of the low-field magnetoresistance (MR) effect. Compared with the La _0.7Sr _0.3CoO ₃ bulk and non-core-shell nanoparticles, the core-shell nanoparticles exhibit enhanced MR.