Investigations on structural disorder-induced modifications in the transport behaviour of rare-earth manganites

Abstract

The results of the studies on structural disorder-induced modifications in the transport behaviour of La0.5Pr0.2Ca0.3−x Ba x MnO3 (LPCBMO) (0.05 ≤ x ≤ 0.30) manganites were reported. Structural studies using X-ray diffraction (XRD) measurements confirmed the single phasic nature of all the samples without any detectable impurities. The A-site size disorder ( ${ {\sigma }}_{\mathrm{A}}^{\mathrm{2}}$ ) increased from 3.81 × 10 −5 (x = 0.05) to 14.9 × 10−5 (x = 0.30). With the increase in structural disorder in LPCBMO system, the transport improved for the range: 0.15 ≤ x ≤ 0.30, which can be ascribed to the enhancement in one electron bandwidth which dominates over the structural disorder effect, while for lower values of x, strong competition existed between size disorder and one electron bandwidth. Below 50 K, all ρ–T plots showed resistivity minimum behaviour, which modified with disorder. This behaviour was discussed in detail on the basis of electron–electron interaction having the form: $ {\rho } {=} {[}\mathrm{1} {/} {(} {\sigma }_{\mathrm{0}} {+} {BT}^{\mathrm{1 {/}2}} {)} {]} {+} {\rho }_{ {n}} {T}^{ {n}}$ . Variation in temperature sensitivity with disorder was also discussed in context of granular morphology and phase segregation scenario.