Novel Dynamical Magnetoelectric Effects in Multiferroic BiFeO_{3}

Area of Science:

• Condensed Matter Physics
• Materials Science
• Multiferroics

Background:

• Multiferroic materials like BiFeO3 exhibit coupled electric and magnetic properties.
• Understanding the dynamic magnetoelectric response is crucial for device applications.

Purpose of the Study:

• Investigate the frequency-dependent response of BiFeO3's electrical polarization and magnetization to AC magnetic fields.
• Characterize the dynamical quadratic magnetoelectric coefficient.
• Identify novel phenomena and quasiparticles governing magnetoelectric coupling.

Main Methods:

• Atomistic effective Hamiltonian scheme within molecular dynamics simulations.
• Analysis of time-dependent electrical polarization and magnetization under varying AC magnetic field frequencies.
• Examination of system behavior with both frozen and relaxed homogeneous strain.

Main Results:

• Electromagnonic vibrations observed at phonon frequencies when strain is frozen.
• Monotonic and dispersionless quadratic magnetoelectric coefficient in the sub-THz range for frozen strain.
• Emergence of strain-mediated oscillations and resonances in the quadratic magnetoelectric coefficient when strain is relaxed.
• Discovery of a new quasiparticle, the "electroacoustic magnon," resulting from phonon-magnon mixing.

Conclusions:

• The study reveals distinct magnetoelectric coupling behaviors based on strain relaxation.
• The "electroacoustic magnon" offers a new avenue for enhancing dynamical magnetoelectric effects.
• Experimentalists can tune sample properties to exploit magnetostrictive-induced resonances for improved magnetoelectric coupling.