Digital Synthesis: A pathway to new materials and novel collective states

Anand Bhattacharya
Materials Science Division and Center for Nanoscale Materials, Argonne National Laboratory

TThe complex oxides of the perovskite family have a very diverse range of collective states, with properties that range from High-T_C superconductivity to half metallic ferromagnetism and multiferroicity. These properties arise as a result of correlations and interplay between their electronic, magnetic and lattice degrees of freedom. Using molecular beam epitaxy based techniques, these materials can often be brought together in heterostructures with atomically sharp interfaces. Such interfaces may provide an opportunity for the correlated degrees of freedom in these materials to ‘reconstruct’ in novel ways, giving rise to collective states that might be distinct from those found in either constituent. We have explored this idea in the context of the manganites. LaMnO₃ and SrMnO₃, both antiferromagnetic insulators, are end members of the La_1-xSr_xMnO3 phase diagram which includes a highly spin-polarized ferromagnetic metal and a variety of antiferromagnets. We have synthesized superlattices of (LaMnO₃)_p/(SrMnO₃)_q where p, q are integers. In this talk, I will discuss the properties of these ‘digital manganites’ where, depending upon the choice of p and q, we can obtain a ferromagnetic metal, interfacial ferromagnetism, and superlattices with enhanced Néel temperatures. We will discuss these results in light of the interfacial effects that may be responsible for the properties of these digital materials.