Negative Piezoelectric Coefficient in Ferromagnetic 1H-LaBr2 Monolayer
Mohammad Noor-A-Alam1, Michael Nolan1
1Tyndall National Institute, University College Cork, Lee Maltings, Dyke Parade, T12 R5CP Cork, Ireland.
ACS Applied Electronic Materials
|February 28, 2022
Summary
This study reveals that intrinsic magnetic and semiconducting 2D materials like 1H-LaBr2 and 1H-VS2 exhibit superior piezoelectric properties compared to non-magnetic 1H-MoS2. These findings pave the way for advanced multifunctional spintronic and piezoelectric devices.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Two-dimensional (2D) magnetic materials with piezoelectric responses are crucial for next-generation nanoscale devices.
- Existing 2D piezoelectrics like 1H-MoS2 lack intrinsic magnetism, limiting their application scope.
- Combining piezoelectricity and magnetism in 2D materials is essential for multifunctional applications.
Purpose of the Study:
- To investigate and compare the piezoelectric properties of intrinsic magnetic and semiconducting 2D materials: 1H-LaBr2 and 1H-VS2 monolayers.
- To analyze the underlying mechanisms responsible for the observed piezoelectric behavior, including electronic and ionic contributions.
- To explore the influence of magnetic ordering on the piezoelectric response in these materials.
Main Methods:
- Density Functional Theory (DFT) calculations were employed to simulate and analyze the piezoelectric properties.
- Calculations included piezoelectric strain coefficients (d11), piezoelectric stress coefficients (e11), elastic constants (C11, C12), and Born effective charges (Z11).
- Analysis focused on the electronic band gap, noncentrosymmetric structure, and time-reversal symmetry breaking.
Main Results:
- Ferromagnetic 1H-LaBr2 and 1H-VS2 monolayers exhibit larger piezoelectric strain coefficients (d11) than 1H-MoS2.
- 1H-LaBr2 shows a negative d11 (-4.527 pm/V) due to a dominant negative ionic contribution, while 1H-VS2 and 1H-MoS2 show positive d11.
- A sign reversal in Born effective charges for Mo and S in 1H-MoS2 contributes to its high piezoelectric stress coefficient (e11).
Conclusions:
- Intrinsic magnetic 2D materials like 1H-LaBr2 and 1H-VS2 offer enhanced piezoelectric performance for spintronic and piezoelectric devices.
- The distinct origins of piezoelectricity in these materials (ionic vs. electronic contributions) provide pathways for tailored device design.
- Modulating magnetic order presents a novel strategy to tune the piezoresponse of 2D magnetic materials.
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