In Nd0.7Sr0.3MnO3 films, ranging in peak resistivity from 1000 Ω-cm to ≤1 Ω-cm, and exhibiting large magnetoresistance effects, the zero-field resistivity above the peak temperature Tp exhibits thermally activated behavior with an activation energy of 0.115±0.005 eV. At T well below Tp, the magnetoconductivity, rather than the magnetoresistance, is linear in B and this linear dependence is observed over a wide B range even when the magnetization is essentially saturated. A cross-over from the linear relation to σ increasing as B2 is observed near and above Tp. A tentative model is proposed.
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Acknowledgments.-T he authorsw ould like to thanku seful discussions with D. Drew and S.C. Wu, and the help of S. E. Lofland, X.G. Jiang, 5. Wu, X.X. Xi, C. Kwon and S.N. Mao. R.L.G. and T.V. acknowledge partial support from NSF contract No. DMR9510475. G.C.X. thanks the IUEP Committeeo f the University of Maryland. M.D. and J.M.B. thank the DGICYT (Spain) and the NRC, respectively,f or a postdoctorafle llowship.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Materials Chemistry