Thickness dependence of the exchange bias in epitaxial manganite bilayers

Abstract

Exchange bias has been studied in a series of ${\text{La}}_{2/3}{\text{Ca}}_{1/3}{\text{MnO}}_{3}/{\text{La}}_{1/3}{\text{Ca}}_{2/3}{\text{MnO}}_{3}$ bilayers grown on (001) ${\text{SrTiO}}_{3}$ substrates by ozone-assisted molecular-beam epitaxy. The high crystalline quality of the samples and interfaces has been verified using high-resolution x-ray diffractometry and $Z$-contrast scanning transmission electron microscopy with electron-energy-loss spectroscopy. The dependence of exchange bias on the thickness of the antiferromagnetic layer has been investigated. A critical value for the onset of the hysteresis loop shift has been determined. An antiferromagnetic anisotropy constant has been obtained by fitting the results to the generalized Meiklejohn-Bean model.