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Ultrafast angular momentum transfer in multisublattice ferrimagnets.
N Bergeard1, V López-Flores1, V Halté1
1Institut de Physique et de Chimie des Matériaux de Strasbourg, UMR7504, CNRS et Université de Strasbourg, 67034 Strasbourg, France.
Nature Communications
|March 12, 2014
Summary
Ultrafast laser pulses demagnetize magnetic materials by transferring angular momentum between sublattices. Total angular momentum is conserved initially, but can transfer to an external bath later.
Area of Science:
- Physics
- Materials Science
- Ultrafast Phenomena
Background:
- Femtosecond laser pulses induce ultrafast magnetization changes in magnetic materials.
- Conservation of total angular momentum during ultrafast demagnetization remains an open question.
Purpose of the Study:
- Investigate the ultrafast transfer of angular momentum during demagnetization in ferrimagnetic alloys.
- Determine the role of spin and orbital momenta in ultrafast demagnetization dynamics.
Main Methods:
- Utilized time-resolved X-ray magnetic circular dichroism (XMCD).
- Analyzed spin and orbital angular momenta for each element in CoGd and CoTb films.
Main Results:
- Observed ultrafast demagnetization in ferrimagnetic CoGd and CoTb films within the first hundred femtoseconds.
- Demonstrated that initial demagnetization is driven by local angular momentum transfer between sublattices, conserving total angular momentum.
- Reported ultrafast quenching of magnetocrystalline anisotropy.
- Observed delayed transfer of total angular momentum to an external bath (~150 fs) in CoTb films.
Conclusions:
- Initial ultrafast demagnetization in ferrimagnetic alloys is governed by inter-sublattice angular momentum transfer, not a loss of total angular momentum.
- A delayed transfer of total angular momentum to an external bath can occur, influencing the overall dynamics.
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