Volume 84, Number 2, October 2008
Article Number 27003
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 26 September 2008
EPL, 84 (2008) 27003
DOI: 10.1209/0295-5075/84/27003

Anomalous insulator-metal transition and weak ferromagnetism in Nd0.37Sr0.63MnO3 thin films

R. 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 ($\leqslant$ 0.45 $\mu _{B}$/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 ($\geqslant$ 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-fluctuation$\hbox{--} $induced 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.

© EPLA 2008