Tensile strain effects on magnetic properties in half-doped La0.5Ca0.5MnO3 films

Half-doped La_0.5Ca_0.5MnO₃ (LCMO) manganites, at the boundary of phase transition from ferromagnetic metal to charge-ordered antiferromagnetic insulator, are very sensitive to external perturbations, such as electric field, magnetic fields, and lattice strain . Recently, novel properties are found in half-doped manganese-oxide thin films and heterostructures . Lattice strain plays a critical role in controlling their electronic and magnetic properties . Therefore, the tensile strain effects on magnetic properties of LCMO films are studied by depositing LCMO films on SrTiO₃ (001) substrates with thickness varying from 165 to 622 A . The distribution of lattice-strain in the films was obtained by measuring the depth dependence of in-plane lattice parameter α using a grazing incidence X-ray diffraction (GIXRD) . It remains tensile-strain state for films with thickness below 50 nm, while most of tensile-strain is relaxed for films with thickness above this value . Magnetic measurements show that the ferromagnetic (FM) transition temperature (TC) of the films keep almost the same value of 250K for films under tensile strain, and it increases to 265K for films under relaxed state . Meanwhile, the magnetization at 10 K increases from 2188 to 4388 emu/cm³ with lattice strain evolves from tensile to relaxed state . The lattice distortion of the films, investigated by temperature dependence of Raman scattering spectra, indicates that the charge ordering is restrained, and the rotation and breathing modes are enhanced by the in-plane tensile strain . The lattice-strain modulated magnetic properties were explained by considering lattice distortion evolution .