Composition-modulated hybrid tunnel junctions of La1－xSrxMnO3

Abstract

Tunnel magnetoresistance junctions with the structure of SrTiO３-sub/ La0.7Sr0.3MnO３(100nm)/La0.96Sr 0.04MnO３ (5nm)/La0.7Sr0.3MnO３ (100nm)/Ir２２Mn７８(15nm)/Ni７９Fe２１(5nm)/Pt(20nm) were micro-fabricated with lithography and Ar ion etching. T he first three epitaxial layers of La0.7Sr0.3MnO３(100nm)/La0.96Sr0.04MnO３ (5nm)/La0.7Sr0.3MnO３ (100nm) were deposited on single crystal (0 01) SrTiO３-substrate by magnetron sputtering and heat treatment, the n the spinning and top conducting layers of Ir２２Mn７８(1 5nm)/Ni７９Fe２１(5nm)/Pt(20nm) were continuously fabricat ed on top the three epitaxial layers by normal magnetron sputtering. The coloss al TMR ratio of 3270% was observed at 4.2K under the external magnetic field of 8 T. The polarization value of 97% for the La0.7Sr0.3MnO３ is well consistent with the theoretical value of 100%. The present r esults directly indicate the half-metallic ferromagnetism in La0.7Sr0.3MnO３. The high TMR value can possibly be attributed to the good interface due to the perfect barrier.