Half-metallic ferromagnetism via the interface electronic reconstruction in LaAlO _3/SrMnO _3 nanosheet superlattices

摘要

Spintronic devices are very important for future information technology. Suitable materials for such devices should have half-metallic properties with only one spin channel conducting. Nanostructures have played an important role in this aspect. Here, we report the realization of robust half-metallic ferromagnetism via the interface electronic reconstruction in artificial LaAlO _3/SrMnO _3 nanosheet supperlattices. On the basis of first-principles density-functional calculations, we reveal an obvious electron transfer from the (LaO) ~+ layer to the adjacent (MnO _2) ~0 layer. And the partially occupied e _g orbitals at the Mn sites can mediate a half-metallic state via a Zener double-exchange mechanism. On the other hand, for the superlattices with a (SrO) ~0/(AlO _2) - interface, hole transfer at the interface is identified. These transferred holes reside mainly at oxygen sites in SrMnO _3, leading to either the preserved G-type AFM ordering in pp-type superlattices or complex magnetic ordering in np-type superlattices. Interestingly, when these systems transit to ferromagnetic ordering by an external magnetic field, an obvious change of electronic state at the Fermi level is found, suggesting a large magnetoresistive effect therein. Our studies demonstrate the unique electric and magnetic properties arising from a magnetic ordering dependent charge transfer and electronic reconstruction at perovskite heterointerfaces, and their potential applications in spintronic devices.