Electronic phase derived impedance spectroscopic behavior of La0.5Nd0.2A0.3MnO3 manganites

• Published in: Journal of alloys and compounds 2021-12, Vol.885, p.160930, Article 160930
• Main Authors: Vadgama, V.S., Gadani, Keval, Udeshi, Bhagyashree, Gal, Manan, Rathod, K.N., Boricha, Hetal, Shrimali, V.G., Solanki, Sapana, Zankat, Alpa, Pachchigar, Vivek, Trivedi, R.K., Joshi, A.D., Ranjan, M., Solanki, P.S., Shah, N.A., Pandya, D.D.
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Annealing; Atomic force microscopy; Charge transport; Crystal structure; Crystallinity; Electrical properties; Grain boundaries; Grain growth; Impedance; Lorentz force; Magnetic fields; Magnetization; Manganites; Nyquist plots; Phase separation; Phase transitions; Pulsed laser deposition; Pulsed lasers; Reactance; Resistance; Substrates; Thin films
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2021.160930

•Prominent effects of divalent dopant on structural behavior and thin film growth.•Significant influence of oxygen annealing on the morphological nature of the surface.•Role of phase separation scenario in electrical properties of mixed valent manganites.•Grain and grain boundary contributions to a complex impedance behavior.•Double magnetic phase transitions in La0.5Nd0.2Ca0.3MnO3 / Al2O3 films.•Phase separation scenario based magnetic fluctuations in La0.5Nd0.2Sr0.3MnO3 / Al2O3 films. [Display omitted] In the present communication, structural, microstructural and electrical properties of La0.5Nd0.2Ca0.3MnO3 (LNCMO) and La0.5Nd0.2Sr0.3MnO3 (LNSMO) mixed valent manganite films, grown on single crystalline (0001) Al2O3 (ALO) substrates using pulsed laser deposition (PLD) technique, have been studied. After deposition, one set of LNCMO and LNSMO films were annealed in oxygen environment at 500 °C (hereafter referred as LNC–A & LNS–A, respectively) and compared their properties with other set of PLD as–grown LNCMO and LNSMO films (hereafter referred as LNC and LNS, respectively). Single crystalline growth of LNCMO films and polycrystalline growth of LNSMO films have been identified through X–ray diffraction (XRD) measurement. Atomic force microscopy (AFM) measurement for morphological studies indicates that divalent dopant and oxygen annealing process play an important role in governing the grain growth and surface nature of the studied films. A decrease in the value of resistance (R) and impedance (Z) with increase in frequency under the applied magnetic field (H = 1 T) has been observed for all the studied films. For LNC & LNC–A films, reactance is found to decrease monotonically with increase in frequency throughout its range studied while for LNS and LNS–A films, reactance initially increases followed by reduction in its value with increase in frequency under 0 and 1 T magnetic field has been observed. The variation in MR for LNS and LNS–A films has been discussed in the context of charge transport mechanism and Lorentz force. Further, to discuss the role of grain and grain boundaries, nyquist plots and their suitable fits under zero and 1 T external magnetic field have been investigated for all the studied mixed valent manganite films. Important role of phase separation scenario in studied manganite films has been discussed in detail based on magnetization measurement. Double magnetic phase transition and fluctuations in derivative of magnetization have