Magneto-transport properties of Fe-doped LSMO manganites Leena Joshi, Sunita Keshri ⇑ Department of Applied Physics, Birla Institute of Technology, Mesra, Ranchi 835 215, Jharkhand, India article info Article history: Received 8 October 2009 Received in revised form 4 June 2010 Accepted 23 February 2011 Keywords: LabVIEW Virtual instrument CMR Magneto-transport properties Bond percolation model abstract Magneto-transport measurements have been performed on La 0.67 Sr 0.33 Mn 1x Fe x O 3 (x = 0.0, 0.05 and 0.07) manganites synthesized by solid state route. The overall nature of AC sus- ceptibility is found to be frequency independent. With the substitution of Mn by Fe, the transport properties dramatically change suppressing the double-exchange interaction. This in turn weakens the ferromagnetism and consequently decreases the paramagnetic to ferromagnetic transition temperature (T c ). However, DC electrical resistivity of the sam- ples show board hump at metal–insulator transition temperature (T MI ) in contrary with sharp transition at T c and T MI < T c indicating decoupling of electrical and magnetic proper- ties. Resistivity behavior of these samples can be well explained by the consideration of bond percolation model which is basically developed from effective approximation method. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction From many decades Perovskite manganites of type R 1x A x MnO 3 where R is La 3+ , Pr 3+ , Nd 3+ and A is Ca 2+ , Sr 2+ ; have been the focus of interest because of their unu- sual magnetic and transport properties, especially the colossal magnetoresistance (CMR) [1,2]. These materials have potential applicability as magnetic sensors, hard disks, infrared detectors, etc. [3–5]. The properties of these materials are governed by several factors such as method of preparation, percentage and size of divalent ions. Tradi- tionally properties of CMR have been explained on the ba- sis of double exchange (DE) and/or superexchange interactions, charge localization via Jhan–Teller distortion with polaron formation, phase separation and site disor- der. Still due to complexities involved there has been a dis- agreement on the theoretical explanation of CMR behavior. Among such materials, La 1x Sr x MnO 3 is of particular interest as the sample with x = 0.3 of this series possesses the largest ferromagnetic (FM) ordering temperature nearly equal to 370 K [6]. These compositions with x = 0.1–0.3 are explored for application as solid oxide fuel cell materials [7,8] also. Moreover, from fundamental point of view, these samples possess large bandwidth due to which substitution at Mn site is supposed only to alter the magnetic and transport properties without taking into account the electron–phonon interactions which is the characteristic of narrow bandwidth compositions. Despite the long history of such work, studies on such series with Fe-substitution at Mn site are comparatively less explored. For example, Mostafa et al. [9] have studied Mössbauer spectroscopy and electrical resistivity behavior of La 0.7 Sr 0.3 Mn 1x Fe x O 3 (x = 0.05, 0.06 and 0.07) samples, but not their PM––FM transition behavior. Huo et al. [10] have observed insulating resistive behavior for La 1x Sr x Mn 1x Fe x O 3 (0:3 6 x 6 0:7) series. So, more exten- sive work on such samples is still required. The substitu- tion of Fe at Mn site is of particular interest because of the large extent to which it can replace Mn without any structural deformation, as both have similar ionic radii having values 0.645 and 0.64 Å for Fe 3+ and Mn 3+ respec- tively. Since the spin, charge, lattice and orbital degrees of freedom are intimately linked to the Mn ion, any pertur- bation at the Mn site is expected to modify ground state properties of such manganites. In this work, we report the structural and magneto-transport properties of 0263-2241/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.measurement.2011.02.005 ⇑ Corresponding author. Fax: +91 651 2275401. E-mail addresses: s_keshri@bitmesra.ac.in, sskeshri@rediffmail.com (S. Keshri). Measurement 44 (2011) 938–945 Contents lists available at ScienceDirect Measurement journal homepage: www.elsevier.com/locate/measurement