Growth and characterization of La1−xAxMnO3 (A=Ag and K, x=0.33) epitaxial and polycrystalline manganite thin films derived by sol–gel dip-coating technique

Manganite La0.67Ag0.33MnO3 (LAgMO) and La0.67K0.33MnO3 (LKMO) films have been obtained on a single-crystal of LaAlO3 (100) and quartz substrates using sol–gel dip-coating technique. Structural, electrical, magnetic and magnetoresistance properties of the films have been investigated. X-ray diffraction patterns of the films grown on LaAlO3 (100) substrate showed to be highly oriented in the direction of (100) and the films grown on the quartz substrate have perovskite with rhombohedral structure. The oriented films exhibited typical transport properties, whereas the polycrystalline films showed significantly different behaviors of the temperature dependent resistivity, magnetization and magnetoresistance (MR). The epitaxial films of the LAgMO and LKMO showed different metal-insulator transition temperature (TMI) and the paramagnetic–ferromagnetic phase transition temperature (TC). This was mainly due to the different ionic radius size of Ag1+ and K1+. The variation of TMI and TC was due to the different annealing temperatures and grain size effect in the polycrystalline films. The polycrystalline films showed a higher MR than the corresponding epitaxial films. An extrinsic MR has been observed at low temperatures (< 100 K) for the polycrystalline films due to the spin dependent scattering of conduction electrons at grain boundaries. Highlights ► Sol–gel derived epitaxial and polycrystalline La0.67Ag0.33MnO3 and La0.67K0.33MnO3 films. ► The polycrystalline thin films show a spin-glass behavior at low temperatures. ► Abrupt rise of magnetization of polycrystalline films at around 50 K. ► Polycrystalline films have higher magnetoresistance than epitaxial films.