Magnetic susceptibility, spin transition, and electrical conductivity of LaCo1 + x O3 and NdCo1 + x O3

The magnetic susceptibility of Nd2O3, NdCo1 + x O3, and LaCo1 + x O3 (x = ,0.0,0.,0.15) has been measured at temperatures from 80 to 950 K, and the electrical conductivity of the neodymium and lanthanum cobaltites (enriched in cobalt relative to neodymium or lanthanum) with the general formulas Nd(La)Co1 + x O3 + 1.5x , or Nd1/(1 + x)(La)1/(1 + x)CoO(3 + 1.5x)/(1 + x), has been measured between 300 and 1050 K. The effective magnetic moments of paramagnetic ions have been determined in the temperature ranges of CurieWeiss behavior and have been used to evaluate the fractions of low-, intermediate-, and high-spin Co ions. Raising the temperature from 320 to 660 K (non-Curie-Weiss behavior) increases the fraction of high-spin Co ions in LaCo1 + x O3 + 1.5x (La1/(1 + x)CoO(3 + 1.5x)/(1 + x) from 27-43 to 56-61%. Moreover, in this temperature range the conductivity of the lanthanum cobaltites rises most steeply. In the range 660-950 K, no spin transition occurs in LaCo1 + x O3 + 1.5x , the slope of the conductivity versus temperature curves gradually decreases, and the conductivity gradually saturates. The conductivity of NdCo1 + x O3 + 1.5x (Nd1/(1 + x)CoO(3 + 1.5x)/(1 + x)) varies considerably in the range 550-950 K, and the spin transition in these cobaltites takes place between 260 and 760 K. Above 760 K, the NdCo1 + x O3 + 1.5x cobaltites with x = 0.05 and 0.10 contain, respectively, 72 and 83% high-spin Co ions and 28 and 17% high-spin Co ions, whereas neodymium cobaltite with x = 0.15 contains 83% high-spin and 17% intermediate-spin Co ions.