Low-temperature resistivity ofLa0.7Sr0.3MnO3ultra thin films: Role of quantum interference effects

Abstract

The low-temperature $(<60\mathrm{K})$ transport properties of as-grown ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}\mathrm{Mn}{\mathrm{O}}_3$ ultrathin films, deposited by the molecular beam epitaxy, have been investigated as a function of the sample thickness (from $40\text{to}3.5\mathrm{nm}$) and in the presence of an external magnetic field. With decreasing thickness, a clear low-temperature resistivity minimum slightly affected by the application of the magnetic field has been observed, and its presence has been possibly interpreted in terms of quantum interference effects. As a function of the thickness, a crossover from a three-dimensional (3D) to a two-dimensional (2D) behavior of the system takes place below $20\mathrm{nm}$. A re-entrant 3D behavior is induced in ultrathin films by the application of large $(>20\mathrm{kOe})$ magnetic fields. Negative values of the magnetoresistance have been observed in all of the investigated samples for all of the measured magnetic fields.