Magneto-transport and ferromagnetic resonance studies of polycrystalline La 0.6Pb 0.4MnO 3 thin films

• Published in: Solid state communications Vol. 137; no. 8; pp. 456 - 461
• Main Authors: Singh, Ajay, Chowdhury, P., Padma, N., Aswal, D.K., Kadam, R.M., Babu, Y., Kumar, M.L. Jayanth, Viswanadham, C.S., Goswami, G.L., Gupta, S.K., Yakhmi, J.V.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 2006
• Subjects: A. CMR films; C. Colossal magnetoresistance; C. Grain boundaries; E. Ferromagnetic resonance; C. Colossal magnetoresistance; C. Grain boundaries; 75.47.Lx; A. CMR films; 07.57.Pt; E. Ferromagnetic resonance; 75.47.GK
• ISSN: 0038-1098; 1879-2766
• DOI: 10.1016/j.ssc.2005.12.015

To understand the nature of grain boundaries in polycrystalline materials, magneto-transport and ferromagnetic resonance measurement have been performed in polycrystalline La 0.6Pb 0.4MnO 3 (LPMO) thin films prepared by pulsed laser deposition. Films are found to undergo a semiconductor to metal transition at 230 K and re-enter into the semiconducting state below 130 K. Microwave absorption measurements carried out as function of applied field show two components of resonant absorption signal. First component is in accordance with ferromagnetic transition of grains at Curie temperature and the second component shows antiferromagnetic transition of grain boundaries at 160 K. An additional non-resonant absorption signal centered at zero field has also been observed that supports transition from conducting to insulating grain boundaries at ∼160 K. Further, temperature dependence of resistance in semiconducting state at low temperatures is in accordance with coulomb blockade model indicating insulating nature of AFM grain boundaries.