Magneto-transport characteristics of La1.4Ca1.6Mn2O7 thin film deposited by spray pyrolysis

TL;DR

This study investigates the magnetic and transport properties of La1.4Ca1.6Mn2O7 thin films deposited via spray pyrolysis, revealing ferromagnetic transitions, variable range hopping conduction, and notable magnetoresistance effects.

Contribution

First detailed analysis of magneto-transport in spray pyrolysis-deposited La1.4Ca1.6Mn2O7 thin films highlighting their magnetic transitions and conduction mechanisms.

Findings

Ferromagnetic transition at ~107K

Insulator-metal transition at ~55K

Magnetoresistance of ~5% at 77K and 0.6 kOe

Abstract

Polycrystalline thin films of double layer manganite La_1.4Ca_1.6Mn_2O_7 (DLCMO) have been deposited by nebulized spray pyrolysis on single crystal LaAlO_3 substrates. These single phase films having grain size in the range 70-100 nm exhibit ferromagnetic transition at T_C ~ 107K. The short range ferromagnetic ordering due to in plane spin coherence is evidenced to occur at a higher temperature around 225 K. Insulator/semiconductor to metal transition occurs at a lower temperature T_P ~ 55K. The transport mechanism above T_C is of Mott`s variable range hopping type. Below T_C the current-voltage characteristics show non-linear behaviour that becomes stronger with decreasing temperature. At low temperatures below T_CA ~ 30K a magnetically frustrated spin canted state is observed. The DLCMO films exhibit resonable low field magnetoresistance and at 77K the magnetoresistance ratio is ~ 5% at 0.6 kOe and \~ 13% at 3 kOe.