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Spatially Resolved Large Magnetization in Ultrathin BiFeO3
Er-Jia Guo1, Jonathan R Petrie2, Manuel A Roldan3
1Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
Advanced Materials (Deerfield Beach, Fla.)
|June 20, 2017
Summary
We found enhanced magnetization in bismuth ferrite (BiFeO3) layers within superlattices, driven by interfaces with lanthanum strontium manganite (La0.7Sr0.3MnO3). This magnetic order persists up to 200 K, suggesting interface effects are key.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Magnetism
Background:
- Bismuth ferrite (BiFeO3) and lanthanum strontium manganite (La0.7Sr0.3MnO3) are multiferroic and ferromagnetic materials, respectively.
- Superlattices combining these materials offer potential for novel electronic and magnetic properties.
- Understanding interfacial magnetic coupling is crucial for device applications.
Purpose of the Study:
- To quantitatively determine the magnetic depth profile in BiFeO3/La0.7Sr0.3MnO3 superlattices.
- To investigate the origin of enhanced magnetization in BiFeO3 layers.
- To explore the influence of layer thickness and temperature on magnetic ordering.
Main Methods:
- Polarized neutron reflectometry was employed to obtain quantitative magnetic depth profiles.
- Superlattices with varying BiFeO3 layer thicknesses were fabricated and analyzed.
- Magnetic moments were measured as a function of depth and temperature.
Main Results:
- An enhanced magnetization of 1.83 ± 0.16 μB/Fe was observed in BiFeO3 layers sandwiched between La0.7Sr0.3MnO3 layers.
- This enhanced magnetic order in BiFeO3 persists up to 200 K.
- The interfacial magnetic effect extends 3-4 unit cells into the BiFeO3 layer, while the interior remains weakly magnetic.
Conclusions:
- The enhanced magnetization in BiFeO3 is attributed to strong orbital hybridization between Fe and Mn at the interfaces, not charge transfer, intermixing, strain, or octahedral distortions.
- This interfacial orbital reconstruction dictates the temperature dependence and upper limit of the magnetic ordering in BiFeO3.
- The findings provide critical insights into interfacial magnetism in multiferroic/ferromagnetic heterostructures.
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