Crystallographic, magnetic, and electrical properties of thin Re 0.6Ba0.4MnO3 epitaxial films (Re = La, Pr, Nd, Gd)

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Thin Re 0.6 Ba 0.4 MnO 3 epitaxial films ( Re = La, Pr, Nd, Gd) grown on (001)SrTiO 3 and (001)ZrO 2 (Y 2 O 3 ) single crystal substrates have been prepared and studied. All the films were found to have a cubic perovskite structure, with the exception of the film with Re = La, which revealed rhombohedral distortion of the perovskite cell. The temperature dependences of the electrical resistivity and magnetoresistance pass through a maximum near the Curie point T C , where the magnetoresistance reaches a colossal value. The magnetization isotherms M ( H ) are superpositions of a magnetization that is linear in field (like that of an antiferromagnet) and a weak spontaneous magnetization. The magnetic moment per formula unit is substantially smaller than that expected under complete ferro-or ferrimagnetic ordering. The magnetizations of samples cooled in a magnetic field (FC samples) and with no field applied (ZFC samples) differ by an amount that persists up to the highest measurement fields (50 kOe). The M ( T ) dependence obtained in strong magnetic fields is close to linear. Hysteresis loops of the FC samples are shifted along the field axis. The above magnetic and electric properties of thin films are explained in terms of two coexisting magnetic phases, which are due to strong s-d exchange coupling.