Low-pressure air plasma induced modification of structural and electrical properties of Gd_1−xSr_xMnO₃ manganites

Abstract

The structural and electrical properties of Gd_1−xSr_xMnO₃ manganites pellets with different doping concentrations x (= 0.2,0.3,0.4,0.5) are modified using an easy low-pressure plasma irradiation method. Powder x-ray diffraction studies of the samples revealed that lattice parameters a and c increase with doping as well as plasma exposure except for x = 0.5 for which a decreases. On the contrary, lattice parameter b decreases with doping as well as plasma exposure and is more pronounced. The crystallite size increases with increasing doping concentration both with or without plasma exposure. Plasma exposure tends to decrease the Mn–O–Mn bond angle as well as the Mn–O bond length. The temperature-dependent electrical resistivity of samples reveals that the pristine Gd_1−xSr_xMnO₃ exhibits insulating behavior for all the doping concentrations. However, the resistivity is enhanced at low temperature for all samples after plasma exposure. The variation of electrical resistivity after plasma exposure may be attributed to the disorder near the grain boundaries and cell volume. The resistivity behavior is unaffected by plasma exposure for all samples. The small polaron hoping model explains the conduction mechanism at high temperature while the conduction at low temperature is attributed to variable range polarons.

KEYWORDS:

• Plasma irradiation
• structural properties
• electrical resistivity
• manganites

Acknowledgements

The authors would like to thank the referee for his valuable comments and suggestions for further improving the quality of the article.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

One of the authors (Ashok Rao) acknowledges Department of Atomic Energy, Government of India, Board of Research in Nuclear Sciences, Government of India for financially supporting this work (2011/34/22/BRNS).

Notes on contributors

Pronita Chettri

Pronita Chettri, Assistant Professor in the department of Physics at Sikkim Manipal Institute of Technology, Majitar, Sikkim, India. Her research interest primarily lies in the effect of radiation on the structural and transport properties of perovskite manganites. She also works in TMDs for sensor applications.

B. S. Nagaraja

Dr. B. S. Nagaraja, Assistant Professor at NMAM Institute of Technology, Nitte, Karkala, and Karnataka, India. His research area is focused on the Manganite's and Radiation effect on manganite's prepared by solid state method. He is particularly interested in understanding behavior of structural, electrical, magnetic and thermoelectric properties of manganites with and without radiations effects.

Ashok Rao

Dr. Ashok Rao is working as a Professor in the department of Physics, Manipal Institute of Technology, Manipal, MAHE. He specializes in magnetic materials, superconductors and thermoelectrics. He has published over 100 Scopus indexed journal papers and completed number of sponsored research projects.

Utpal Deka

Dr. Utpal Deka is working as an Additional Professor in the Department of Physics, Manipal Institute of Technology Bengaluru, Manipal Academy of Higher Education, Manipal, India. He specializes in the area of plasma physics, plasma material interaction, plasma instabilities, nonlinear plasma, etc. He has published more than 70 research articles in journals and conferences and completed number of sponsored research projects.