Electrical transport properties and enhanced magnetoresistance effect in double perovskite La_2–xCa_xCoMnO₆ (0 ≤ x ≤ 0.5)

Abstract

Polycrystalline La2–x Ca x CoMnO6 (0 ≤ x ≤ 0.5) samples were synthesized by the standard solid‐state reaction. The crystal structure of the samples was monoclinic perovskite structure with space group of P21/n at room temperature. All the samples show semiconducting‐like behavior and the nature of electrical conduction can be well described by Mott's three‐dimensional variable range hopping model. A large negative magnetoresistance effect is observed in all samples, which may be caused by the suppression of spin‐fluctuations by the magnetic field. A resistor network theory can be appropriate to explain the features of this magnetoresistance effect. Furthermore, the magnetoresistance effect could be regulated by the concentration of Ca2+ ions. The negative magnetoresistance effect of La1.8Ca0.2CoMnO6 can be enhanced to 56% at 120 K under 7 T.

The spontaneous exchange bias effect in La2-xCaxCoMnO6 series

“…The controversy occurs because the Co and Mn scattering factors are very similar for XRD performed with Cu-K α radiation. Different groups have reported such compounds as belonging to one of these space groups or even a mixture of both [18,24,25,26,27,28]. The Co-and Mn-based perovskites are known to be very sensitive to the synthesis route [6,29,30], and the La 2−x Ca x CoMnO 6 seems to be a clear manifestation of this.…”