Influence of ion implantation on the magnetic and transport properties of manganite films

Abstract

We have used ions irradiation to generate controlled structural disorder in thin manganite films.Conductive atomic force microscopy (CAFM) and transport and magnetic measurements were performed toanalyze the influence of the implantation process in the physical properties of the films. CAFM images showregions with different conductivity values, probably due to the random distribution of point defect. Thetransport and magnetic properties of these systems are interpreted in this context. Metal-insulator transition canbe described in the frame of a percolative model. Disorder increases the distance between conducting regions,lowering the observed TMI. Point-defect disorder increases localization of the carriers due to increased disorderand locally enhanced strain field. Remarkably, even with the inhomogeneous nature of the samples, no sign oflow-field magnetoresistance was found. Point-defect disorder decreases the system magnetization but does notseem to change the magnetic transition temperature. The coercive field of the samples increases linearly withincreasing disorder but decreases when disorder is higher than a critical value.