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Tunable Magnetic Phases at Fe3O4/SrTiO3 Oxide Interfaces
Mai Hussein Hamed1,2, Ronja Anika Hinz1, Patrick Lömker1
1Peter-Grünberg-Institut (PGI-6) , Forschungszentrum Jülich GmbH , 52425 Jülich , Germany.
ACS Applied Materials & Interfaces
|January 24, 2019
Summary
We explored magnetic phases in ultrathin magnetite films on SrTiO3. Post-annealing controlled the magnetic interface, enabling stoichiometric ferrimagnetic Fe3O4/SrTiO3 heterointerfaces.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Surface Science
Background:
- Magnetite (Fe3O4) is a ferrimagnetic half-metal crucial for oxide electronics.
- Strontium titanate (SrTiO3) is a transparent nonmagnetic insulator and a foundational material in oxide electronics.
- Understanding interfacial magnetism in Fe3O4/SrTiO3 heterostructures is key for advanced electronic devices.
Purpose of the Study:
- To investigate the emergence and control of magnetic phases at the Fe3O4/SrTiO3 interface.
- To analyze the evolution of the Verwey transition in ultrathin Fe3O4 films.
- To determine the impact of film thickness and annealing on interfacial magnetic properties.
Main Methods:
- Fabrication of ultrathin Fe3O4 films on SrTiO3 substrates.
- Angle-dependent hard X-ray photoelectron spectroscopy (HAXPES) for element-selective electronic properties.
- X-ray magnetic circular dichroism (XMCD) for probing magnetic properties.
- Variable temperature measurements to study the Verwey transition.
Main Results:
- The Verwey transition temperature (TV) in Fe3O4 films decreased from 117 K (38 nm) to 25 K (2 nm).
- A reduction in Fe2+ and an increase in Fe3+ ions were observed with decreasing film thickness, indicating the formation of a gamma-Fe2O3 intralayer.
- Post-annealing successfully reduced the gamma-Fe2O3 intralayer, leading to stoichiometric and ferrimagnetic Fe3O4/SrTiO3 interfaces.
Conclusions:
- The Verwey transition persists in ultrathin Fe3O4 films, but its temperature is thickness-dependent.
- An interfacial gamma-Fe2O3 layer forms in ultrathin Fe3O4 films, influencing magnetic properties.
- Controlled annealing provides a method to manipulate and achieve desired ferrimagnetic Fe3O4/SrTiO3 interfaces.
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