Surface magnetic phase transition of the double-exchange ferromagnet: Schwinger-boson mean-field study

The surface magnetic phase transition of a double-exchange model for metallic manganites is studied using a Schwinger-boson mean-field method. About three unit-cells wide surface layers are identified. The magnetic moment in these layers decreases more rapidly than that in the bulk when the temperature is increased. This behavior is consistent with experimental observations. We also discuss the implication of this behavior to the tunneling magnetoresistance effect using manganites and possible improvement of the magnetoresistance effect near the bulk Curie temperature.