Anomalous insulator-metal transition and weak ferromagnetism in Nd0.37Sr0.63MnO3 thin filmsR. Prasad1, M. P. Singh2, P. K. Siwach1, P. Fournier2 and H. K. Singh1
1 National Physical Laboratory - Dr K. S. Krishnan Road, New Delhi-110012, India
2 Département de Physique and RQMP, Université de Sherbrooke - Sherbrooke-J1K 2R1, Canada
received 1 April 2008; accepted in final form 2 September 2008; published October 2008
published online 26 September 2008
We report thickness-dependent magnetic and transport properties at the boundary separating A- and C-type antiferromagnetic phases in films of the overdoped manganite Nd0.37Sr0.63MnO3. The thin films are prepared by DC magnetron sputtering on single-crystal LaAlO3 substrates. All films, 5-120 nm in thickness, show a paramagnetic-ferromagnetic (PM-FM) transition. The small value of magnetization ( 0.45 /Mn) is suggestive of the weak nature of the FM correlations that is different from the prototype PM-FM transition due to double exchange (DE). At lower film thicknesses, such as 5 and 25 nm, zero-field resistivity shows an insulator-like behavior. An insulator-metal (IM) transition is observed at higher film thicknesses ( 60 nm). The magnetic-field independence of the observed I M transition (TIM ~ 125 K) distinguishes it from the same observed in prototype manganites (x ~ 0.2-0.4) and explained by D E. For the thinnest films, a CMR effect as large as MR ~ 85% is observed in the low-temperature regime. The observed phenomena can be explained in terms of orbital-fluctuationinduced phase separation.
75.47.Lx - Manganites.
73.50.-h - Electronic transport phenomena in thin films.
75.70.-i - Magnetic properties of thin films, surfaces, and interfaces.
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