Stacked Nanosheets of Pr1-xCaxMnO3 (x=0.3 and 0.49): A Ferromagnetic Two-Dimensional Material with Spontaneous Exchange Bias

Two-dimensional (2D) planar architectures of inorganic materials have attracted great attention owing to their fascinating physical properties. However, nanosheets of the technologically relevant doped rare-earth manganites are still elusive. Stacked 10-14 nm thick nanosheets of phase pure Pr1-xCaxMnO3 (PCMO; x = 0.3 and 0.49) were obtained by decomposition of carbon coated CaCO3/MnCO3 microsheets and Pr2O2CO3 aggregates, the latter synthesized under pressure at 500-800 degrees C. The PCMO nanosheets had flatter Mn-O-Mn tilt angles in the MnO6 octahedra and ferromagnetic (FM) moments at 5 K. Spontaneous exchange bias (SEB) coupling between the antiferromagnetic (AF)/FM spins was observed at 5 K under zero-field cooling. High FM moments and SEB were possible due to the long-range magnetic interactions in the stacked 2D arrangement of Mn3+/Mn4+ d-electron spins, where charge ordering was completely suppressed. The SEB behavior was dependent on the initial magnetization process and the direction of rotation of the random spins at the AF/FM interface.