Charge transport mechanisms in sol–gel grown La_0.7Pb_0.3MnO₃/LaAlO₃ manganite films

Abstract

In this communication, structural, microstructural, transport and magnetotransport properties are reported for LaPbMnO/LaAlO (LPMO/LAO) manganite films having different thicknesses. All the films were irradiated with 200 MeV Ag swift heavy ions (SHI). Films were grown using the sol-gel method by employing the acetate precursor route. Structural measurements were carried out using the X-ray diffraction (XRD) method at room temperature, while atomic force microscopy (AFM) was performed for the surface morphology. Temperature dependent resistivity under different applied magnetic fields for all the films shows metal to insulator transition at temperature T. In addition to the metal to insulator transition at T, the films also exhibit low temperature resistivity upturn behavior. Resistivity, T and upturn behavior are highly influenced by the film thickness, applied magnetic field and irradiation. To understand the nature of charge transport for the low temperature resistivity behavior and metallic and insulating (semiconducting) regions, various models and mechanisms have been verified and the most suitable mechanism has been found for each region in the resistivity curves. Magnetoresistance (MR) is affected by temperature, film thickness and irradiation. MR behavior has been understood in terms of combined and separate contributions from grains and grain boundaries in the films.

Interface based field effect configuration and charge conduction mechanisms for manganite thin film heterostructures

“…It is a well known fact that parameter n strongly depends on various external parameters including ionic doping percentage, structural parameters, magnetic nature of the lattice, film thickness, nature of defects existing, interface nature in the devices, externally applied magnetic field, form of the samples under study, externally applied electric field, etc. 31–33,53–59 One magnon scattering processes can be expected for n ∼2.5 and ∼3.0, two magnon scattering processes can be correlated with the values of n ∼4.5 and ∼7.5 and intermediate scattering processes can also be predicted if n is found to be ∼5.5 and 6.5. 31–33 A few reports also deal with the higher order spin fluctuations within the lattice where n is found to be higher than 7.5.…”

“…To understand the charge-lattice or spin-lattice interactions as well as electron-magnon scattering processes that exist across the LMO/LCMO interface grown using the CSD method (CSD method and PLD technique based comparison has been done for LMO/LCMO interface based resistivity behaviors only, other investigations are limited to the chemically grown LMO/ LCMO interface within the scope of the present report), temperature dependent resistivity data have been fitted theoretically using the ZDE polynomial law: r(T) = r 0 + r 2 T 2 + r n T n , where r 0 is the studied lower temperature resistivity (in the present case, r 0 represents the resistivity values recorded at 200 K), r 2 is the resistivity contributed through existing electronelectron, electron-phonon, and electron-magnon scattering processes, r n is the corresponding resistivity coefficient and n is the ZDE polynomial law parameter. [53][54][55][56][57][58][59] In the present case, it is necessary to point out that r 2 is the resistivity contributed by three major scattering processes, namely, electron-electron, electron-phonon and electron-magnon. However, at higher temperatures (i.e.…”

“…It is a well known fact that parameter n strongly depends on various external parameters including ionic doping percentage, structural parameters, magnetic nature of the lattice, film thickness, nature of defects existing, interface nature in the devices, externally applied magnetic field, form of the samples under study, externally applied electric field, etc. [31][32][33][53][54][55][56][57][58][59] One magnon scattering processes can be expected for n B2.5 and Table 1 Values of fitting parameters including r 0 , r 2 , r n and exponent n (with obtained errors for r 0 and power exponent n) along with values of goodness of fit parameter w 2 obtained by fitting the ZDE polynomial law r(T) = r 0 + r 2 T 2 + r n T n to the temperature dependent LMO/LCMO interface resistivity recorded under a zero interface electric field and applied negative and positive interface electric fields across the same LMO/LCMO interface of the LMO/LCMO/LAO structure (please refer the text for clarification of fitting parameters of the ZDE polynomial law) B3.0, two magnon scattering processes can be correlated with the values of n B4.5 and B7.5 and intermediate scattering processes can also be predicted if n is found to be B5.5 and 6.5. [31][32][33] A few reports also deal with the higher order spin fluctuations within the lattice where n is found to be higher than 7.5.…”

“…[31][32][33] A few reports also deal with the higher order spin fluctuations within the lattice where n is found to be higher than 7.5. 32,56 To summarize, in brief, the correlations between the values of the n parameter and the nature of spin-lattice interactions within the manganite lattice, one can state that with the increase in the value of parameter n, the spin fluctuations within the same lattice get enhanced. For the present case of temperature dependent LMO/LCMO interface resistivity under different interface electric fields (both negative and positive electric fields) applied across the same LMO/LCMO interface, the ZDE polynomial law has been fitted nicely, as shown in Fig.…”

Escalated Phase Separation Driven Enhanced Magnetoresistance in Manganite/Iridate Epitaxial Heterostructures

“…The resistance in the FM phases is usually described as a sum of temperature-independent residual resistance R 0 , resistance due to electron-electron scattering AT 2 and resistance due to electron-phonon and electron-magnon interaction BT 5 , [43][44][45][46] i.e., R FM = R 0 +AT 2 +BT 5 . Whereas the insulating behavior in the paramagnetic regime is described based on the thermal activation model, R PI = D exp(E a /k B T), where D is a constant and E a is the activation energy required to hop the electron from the valence band to the conduction band.…”