Tunneling between the metallic antiferromagnetic and ferromagnetic phases of La(1-x)Sr(x)MnO3 near x=0.5 by digital synthesis

Abstract

We investigated cation-ordered La1−xSrxMnO3 about the half-doping level x 0.5 in superlattices of alternating, single unit-cell layers of LaMnO3 and SrMnO3. The effect of La/Sr cation order was addressed by comparing the structural, magnetic and transport properties of these superlattices with random alloy films of equivalent composition. The samples were synthesized by ozone-assisted molecular beam epitaxy onto SrTiO3 substrates. The superlattices could be tuned between ferromagnetic and antiferromagnetic metallic states by inserting extra single unit-cell layers of LaMnO3 and SrMnO3, respectively. For x < 0.5, a ferromagnetic, metallic phase was observed. For x = 0.50 and 0.55, A-type antiferromagnetic order was confirmed by neutron diffraction, with a N´eel temperature of 300 K, significantly higher than bulk values. The enhanced N´eel temperature was attributed to lattice strain rather than cation order.