Electrical conductivity of a single manganite nanotubes: comparison of La2/3Ca1/3MnO3 and La2/3Sr1/3MnO3 systems.

M.E. SALETA; J. LOHR; V. TOGNOLI; J. CURIALE; H. E. TROIANI; A. G. LEYVA; R.D. SÁNCHEZ

Buenos Aires

Workshop; X-Latin American Workshop on Magnetism and Magnetic Materials and their Applications; 2013

Materia Condensada-CAC-CNEA

Due to their possible applications in the nanoelectronic devices, several quasi-1D objects (nanowires, nanotubes, nanobelts) have been thoroughly investigated. Particularly, dierent manganese oxides with perovskites structure are between the most studied materials in the last decade. In this work we compare the behavior of two prototypical systems constituted by assem-bled nanograins. These systems are granular manganite nanotubes (NT) of La2/3Ca1/3MnO3 (LCMO) and La2/3Sr1/3MnO3 (LSMO). The NTs with approximately 800 nm of external diameter have been synthesized by the assisted lling of plastic templates followed by a microwave treatment. Crystallographic analysis conrms the perovskite structure of the compounds, and electron micrographs of the NTs show that both systems consist of nanograins assemblies with an average diameter of 25 nm. Magnetic studies reveal that both samples present ferromagnetic order below Tc = 255 K and Tc = 340 K for LCMO and LSMO respectively. These studies also show that the magnetism is strongly governed by the nanograin size. By using high resolution transmission electron microscopy (HRTEM) we observed a structural disorder layer of 2 nm on the surface of the nanograins. This disordered surface is responsible for a reduction of the magnetization of about 40%, and also avoids a ferromagnetic interaction between the nanograins in the magnetic ordered  state. In addition, Current - Voltage curves were collected from single NTs of both compositions using a nanomanipulator installed in a SEM chamber at room temperature. In that experimental condition, the LCMO NTs were in the paramagnetic state while the LSMO NTs in the ferromagnetic one. We compare the electrical conductivity of both systems, and discuss similarities and dierences in terms of morphological, structural and magnetic properties of each sample.