Heterostructures based on thin films of lanthanum manganites and multiferroic bismuth ferrite

Abstract

We review results of our recent investigations on preparation and electrical properties of thin films and heterostuctures of colossal magnetoresistance manganites and multiferroic BiFeO 3 (BFO). Major attention is paid to the interfaces formed between the oxides, conducting SrTiO 3 and semiconducting organic (Alq3) compound. Thin films of La 2/3A 1/3MnO 3 (A = Ca, Sr, Ba, Ce) and BFO were grown by magnetron sputtering on conducting lattice-matched Nb-doped SrTiO 3 substrates while the organic films were prepared as top layers onto the oxide layers by thermal evaporation. Nonlinear electrical properties and magnetoresistance of the heterostructures have been investigated in a wide temperature range (78 K-400 K). Various mechanisms, i. e. thermoionic emission in a barrier of Schottky type, carrier tunneling through the interfaces and space charge limited current processes were considered to explain nonlinear electrical transport properties in the heterojunctions. Both negative and positive magnetorestance values have been indicated for the heterojunctions formed by growing the manganite films on SrTiO 3 substrates. The Alq3/LSMO heterojunctions demonstrated magnetoresistance values up to 11% (at T = 240 K and B = 1 T).