Effects of ferroelectric-poling-induced strain on magnetic and transport properties of La_0.67Ba_0.33MnO₃ thin films grown on (111)-oriented ferroelectric substrates

La_0.67Ba_0.33MnO₃ thin films were epitaxially grown on (111)-oriented 0.31Pb(In_1/2Nb _1/2)O₃-0.35Pb(Mg_1/3Nb_2/3)O ₃-0.34PbTiO₃ ferroelectric single-crystal substrates. During ferroelectric poling and polarization rotation, the resistance of La _0.67Ba_0.33MnO₃ films tracks the electric-field-induced in-plane strain of substrates effectively, implying strain-mediated coupling. Upon poling along the [111] direction, ferromagnetism is suppressed for T < 175 K, but enhanced for T > 175 K, which is explained by magnetoelastic coupling that modifies the film's magnetic anisotropy. Our findings also show that the magnetic field has an opposite effect on the strain-tunability of resistance [i.e., (ΔR/R)strain] above and below the Curie temperature T_C, which is interpreted within the framework of phase separation.