Peculiar transport properties and CMR effect of La0.67Sr0.08Na0.25MnO3

The La0.67Sr0.08Na0.25MnO3 sample was prepared by solid-state reaction. The transport properties and CMR effect of the sample were studied through M-T curves, ρ-T curves and ρ-T fitted curves. The results show that: Both the ρ-T curves and the MR-T curve exhibit the double-peak phenomenon; the high-temperature peak corresponds to the I-M transition accompanied by the PM-FM transition, and the low-temperature peak is attributed to grain boundary effect. The two insulator phases have different transport mechanisms: in the low temperature range(248 KTρ(T) accords with variable-range-hopping model of polaron, while in the high temperature range(330 KTρ(T) accords with near- neighbor- hopping model of polaron; and the two metal-like phases also have different transport mechanisms: in the low temperature range(67 KTρ(T) accords with the ρ-T2.5 relation, and the transport mechanism is the actions of spin wave scattering and electron-magneton scattering, while in the high temperature range(292 KTρ(T) accords with the ρ-T2 relation, and the transport mechanism is single magneton scattering.