Nonlinear behavior of V-I curves at low temperatures in nanoparticles of La_2/3B_1/3MnO₃ with B = Ca, Sr

We measure voltage-current curves at low temperature in La_2/3B_1/3MnO₃ samples (B=Ca,Sr). The powder oxides were prepared by different wet-chemical routes and low calcination temperatures were used for nanoparticles formation. We studied samples prepared by three different synthesis methods: gel-combustion, urea sol-gel and liquid-mix. Although the average particle size was almost the same for all the samples (∼30 nm), we found different behaviors in the V-I curves depending on the synthesis route. The obtained data are analyzed in the electronic tunneling picture.