Abstract
Artificially fabricated 3$d$/5$d$ superlattices (SLs) involve both strong electron correlation and spin-orbit coupling in one material by means of interfacial 3$d$-5$d$ coupling, whose mechanism remains mostly unexplored. In this work we investigated the mechanism of interfacial coupling in LaMnO$_3$/SrIrO$_3$ SLs by several spectroscopic approaches. Hard x-ray absorption, magnetic circular dichroism and photoemission spectra evidence the systematic change of the Ir ferromagnetism and the electronic structure with the change of the SL repetition period. First-principles calculations further reveal the mechanism of the SL-period dependence of the interfacial electronic structure and the local properties of the Ir moments, confirming that the formation of Ir-Mn molecular orbital is responsible for the interfacial coupling effects. The SL-period dependence of the ratio between spin and orbital components of the Ir magnetic moments can be attributed to the realignment of electron spin during the formation of the interfacial molecular orbital. Our results clarify the nature of interfacial coupling in this prototypical 3$d$/5$d$ SL system and the conclusion will shed light on the study of other strongly correlated and spin-orbit coupled oxide hetero-interfaces.
Highlights
Entanglement of charge, spin, lattice, and orbital degrees of freedom in transition metal oxides (TMOs) has attracted a great amount of research attention recently [1,2,3,4,5]
In this work we investigated the mechanism of interfacial coupling in LaMnO3/SrIrO3 SLs by several spectroscopic approaches
First-principles calculations further reveal the mechanism of the SL-period dependence of the interfacial electronic structure and the local properties of the Ir moments, confirming that the formation of Ir-Mn molecular orbital is responsible for the interfacial coupling effects
Summary
Entanglement of charge, spin, lattice, and orbital degrees of freedom in transition metal oxides (TMOs) has attracted a great amount of research attention recently [1,2,3,4,5]. Great improvement of thin-film fabrication techniques enables accurately controlled design of epitaxial TMO heterostructures and SLs with atomically abrupt interfaces It appears to be a natural strategy that artificial 3d/5d TMO heterostructures or SLs are promising candidates to involve both significant electron correlation and SOC simultaneously. The effectiveness of interfacial coupling effects can be tuned by repetition period of the SLs. Research on the SL-period-dependent evolution of the interfacial electronic structure in manganite-iridate SLs will be informative for understanding the role of interfacial 3d-5d coupling to affect the Ir magnetism, which has not been systematically investigated so far. Research on the SL-period-dependent evolution of the interfacial electronic structure in manganite-iridate SLs will be informative for understanding the role of interfacial 3d-5d coupling to affect the Ir magnetism, which has not been systematically investigated so far For this purpose, we fabricated LaMnO3/SrIrO3 (LMO/SIO) SLs with different repetition periods. First-principles calculations demonstrate a satisfactory consistency with the experimental results and reveal that the formation of the interfacial Ir-Mn molecular orbital associated with concomitant electronic-structure change is the pivotal mechanism behind this SL-period-dependent interfacial coupling
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