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Magnetism of Bi2Se3 thin films with Eu-rich flat inclusions.
L N Oveshnikov1,2, Ya I Rodionov3,4, K I Kugel3,5
1National Research Center 'Kurchatov Institute', Moscow, 123182, Russia.
Journal of Physics. Condensed Matter : an Institute of Physics Journal
|September 13, 2018
Summary
Europium-doped Bi2Se3 thin films show magnetic ordering primarily driven by dipole-dipole interactions between nanoinclusions. This leads to antiferromagnetic ordering within platelet stacks, reducing the average magnetic moment per Eu atom.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Nanotechnology
Background:
- Europium-doped Bi2Se3 thin films exhibit inhomogeneous magnetic properties.
- Europium atoms aggregate into platelet-like nanoinclusions, with their frequency increasing with doping concentration.
- Stacks of these platelets become common at higher Europium content.
Purpose of the Study:
- To investigate the magnetic properties and ordering mechanisms in Eu-doped Bi2Se3 thin films.
- To understand the influence of nanoinclusion distribution on magnetic behavior.
- To theoretically model the magnetic interactions and transition temperature.
Main Methods:
- Experimental studies including electron microscopy to characterize nanoinclusions.
- Magnetic property measurements and comparative analysis of temperature dependence.
- Theoretical analysis of magnetic ordering mechanisms (RKKY, dipole-dipole interactions).
- Application of a metallic spin glass model to estimate transition temperature.
Main Results:
- Europium atoms form platelet-like nanoinclusions, with increased stacking at higher doping levels.
- The average magnetic moment per Eu atom decreases with increasing doping concentration.
- RKKY interaction dominates within platelets, while dipole-dipole interaction governs inter-platelet ordering.
- Antiferromagnetic ordering within platelet stacks explains the observed decrease in magnetic moment.
- A spin glass model provides a satisfactory estimate of the transition temperature, considering finite film thickness.
Conclusions:
- The magnetic ordering in Eu-doped Bi2Se3 films is primarily governed by inter-platelet interactions, specifically magnetic dipole-dipole forces leading to antiferromagnetism in stacks.
- The observed decrease in average magnetic moment is attributed to this antiferromagnetic ordering.
- The findings offer insights into magnetic interactions in nanostructured materials and can inform studies on ultrathin films with similar impurity profiles.
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