Abstract
A variety of emergent phenomena are enabled by interface engineering in the complex oxides heterostructures. While extensive attention is attracted to LaMnO3 (LMO) thin films for observing the control of functionalities at its interface with substrate, the nature of the magnetic phases in the thin film is, however, controversial. Here, it is reported that the ferromagnetism in two and five unit cells thick LMO films epitaxially deposited on (001)‐SrTiO3 substrates, a ferromagnetic/ferromagnetic coupling in eight and ten unit cells ones, and a striking ferromagnetic/antiferromagnetic pinning effect with apparent positive exchange bias in 15 and 20 unit cells ones are observed. This novel phenomenon in both 15 and 20 unit cells films indicates a coexistence of three magnetic orderings in a single LMO film. The high‐resolution scanning transmission electron microscopy suggests a P21/n to Pbnm symmetry transition from interface to surface, with the spatial stratification of MnO6 octahedral morphology, corresponding to different magnetic orderings. These results can shed some new lights on manipulating the functionality of oxides by interface engineering.
Highlights
Artificial oxide heterostructures with chemically abrupt interfaces provide a platform for engineering bonding geometries that lead to emergent phenomena.[1,2,3,4,5,6,7,8] Various interesting properties and diverse phase diagrams have been demonstrated in LaMnO3 (LMO) thin films, multilayers, and superlattices, making the interfaces between LMO and substrates become an ideal candidate for discovering new phenomena for controlling functionalities.[9,10,11,12] Stoichiometric LMO bulk is known to be a layer-type (A-type) antiferromagnet, in which Mn3+ is a Jahn-Teller ion with a t e occupancy and the in-plane interaction between adjacent Mn ions is ferromagnetic (FM) while the out-of-plane one is antiferromagnetic (AFM).[13]
To reveal the evolution of magnetic property in different regions, we show the characterizations by high-resolution scanning transmission electron microscopy (STEM), which display a transition from P21/n to Pbnm structure, corresponding to the evolution of FM to AFM
We studied the evolution of the insulating magnetic LMO thin films and found that three magnetic layers with FM, harder FM, and AFM features arising successively with increasing film thickness
Summary
Artificial oxide heterostructures with chemically abrupt interfaces provide a platform for engineering bonding geometries that lead to emergent phenomena.[1,2,3,4,5,6,7,8] Various interesting properties and diverse phase diagrams have been demonstrated in LaMnO3 (LMO) thin films, multilayers, and superlattices, making the interfaces between LMO and substrates become an ideal candidate for discovering new phenomena for controlling functionalities.[9,10,11,12] Stoichiometric LMO bulk is known to be a layer-type (A-type) antiferromagnet, in which Mn3+ is a Jahn-Teller ion with a t e occupancy and the in-plane interaction between adjacent Mn ions is ferromagnetic (FM) while the out-of-plane one is antiferromagnetic (AFM).[13]. The high-resolution scanning transmission electron microscopy suggests a P21/n to Pbnm symmetry transition from interface to surface, with the spatial stratification of MnO6 octahedral morphology, corresponding to different magnetic orderings.
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