Growth and giant magnetoresistance properties of La-deficient La _xMnO_3-δ (0.67≤x≤1) films

Epitaxial thin films of lanthanum-deficient LaxMnO 3-δ (0.67≤x≤1) have been grown on (100) SrTiO3 substrates by pulsed laser deposition. The as-deposited films exhibit a ferromagnetic transition at temperatures ranging from 115 to 240 K, with the transition temperature (Tc) increasing with higher La deficiency. A sharp drop in resistivity and negative magnetoresistance is observed close to Tc, a behavior similar to that observed in divalent substituted La1-xMxMnO3-δ (M=Ba, Sr, Ca, Pb) films. Postannealing the films in O2 reduces the resistivity and raises the Tc to values close to room temperature. A magnetoresistance value of 130% (Δρ/ρH) has been obtained at 300 K at 4 T for a post-annealed film with x=0.75.© 1995 American Institute of Physics.