IUP Publications Online
Home About IUP Magazines Journals Books Archives
     
Recommend    |    Subscriber Services    |    Feedback    |     Subscribe Online
 
The IUP Journal of Physics :
A Comparison Study of Chemical Solution Deposited (100)-Epitaxial Nd0.7Ca0.3MnO3 and Nd0.7Sr0.3MnO3 Nanocrystalline Thin Films at 800 C
:
:
:
:
:
:
:
:
:
 
 
 
 
 
 

This paper reports a study of the magnetotransport and electrical properties of (100)-oriented Nd0.7(Sr, Ca)0.3MnO3 thin films prepared by an optimized chemical solution deposition process on a (100) LaAlO3 single-crystal substrate. The films were studied by X-Ray Diffraction (XRD), atomic force microscopy, magnetotransport data and four-point-probe electrical measurements. A characteristic nanocrystalline texture with ~22-25 nm crystallites was observed in both the films. The magnetotransport properties were determined as a function of the temperature and applied magnetic field. Both films display large values of colossal magnetoresistance at around room temperature. However, the dependence of these promising properties on the nanocrystal size remains to be explored.

 
 

In the past decade, there have been numerous studies on the colossal magnetoresistance CMR effect of the mixed-valence perovskites: rare earth manganites RE1-XMXMnO3 (RE = rare-earth, M = Ca, Sr, Ba, Pb) (Millis et al., 1996; Ramirez, 1997; Evetts et al., 1998; Tokura, 2000; and Prellier et al., 2001). These CMR oxides in thin-film form are especially attractive for their potential applications in magnetic random access memory, magnetic field sensor, hard disk read-heads and infrared detectors (Steinbei et al., 2000; and Haghiri-Gosnet and Renard, 2003). In addition, understanding the novel transport and magnetotransport properties of these materials is a substantial challenge. One of the fruitful endeavors in this field has been the growth of good quality films with appreciable magnetoresistance (MR) and high ferromagnetic transition temperature (Tc), preferably above 300 K. The magnetic and electrical properties of the films of these Colossal Magneto Resistance (CMR) oxides are very sensitive to the material processing parameters. The magnetotransport properties in these perovskite systems are governed by the well-known double exchange between Mn+3 and Mn+4 pairs as well as the temperature-dependent polaronic interactions that localize charge carriers via Jahn-Teller distortion around the Mn+3O6 octahedras (Tsuda et al., 2000; and Mannella et al., 2004). Epitaxial thin films of Nd0.7Sr0.3MnO3 (NSMO) or Nd0.7Ca0.3MnO3 (NCMO) have been prepared over the last few years by a number of methods, such as Pulsed Laser Deposition (PLD), sputtering, Metal Oxide Chemical Vapor Deposition (MOCVD) and Chemical Solution Deposition (CSD). CSD techniques provide many advantages such as low cost, easy setup and coating of large areas. Control of stoichiometry and uniformity of these films depends highly on the reactivity of the chemicals used in the preparation of solutions. Moreover, film crystallinity, microstructure, and epitaxial relationships to the substrate need to be controlled in order to obtain the highest quality of epitaxial CMR films (Jin et al., 1999). The CMR properties of these films are crucially dependent on the oxygen stoichiometry, and need to be annealed after deposition. Well-characterized experimental data as a function of strain and oxygen deficiency is necessary for comparing the various results published in the literature, and for the use of these materials as commercial magnetoresistive devices. It is therefore important to fabricate and characterize high quality epitaxial films using a simple, inexpensive and reproducible method in which the stoichiometry can be accurately predetermined and controlled. The magnetic and electrical properties of the films of these CMR oxides are very sensitive to the material processing parameters, such as the method of deposition, the temperature of growth, post-deposition annealing treatment (Paranjape and Raychaudhuri, 2002), quality of epitaxy and mismatch with the substrate (Jin et al., 1995).

 
 

Physics Journal, Electrical Transport Properties, Transmission Electron Microscopy, Magnetotransport Data, Antiferromagnetic Semiconductors, Chemical Precipitation Method, Nanocrystalline Manganites, Perovskite Structure, Citrate-gel Method, Polycrystalline Perovskite Material, Debye Scherrer Formula.