Inertial Spin Dynamics in Epitaxial Cobalt Films
Vivek Unikandanunni1, Rajasekhar Medapalli2,3, Marco Asa4
1Department of Physics, Stockholm University, 10691 Stockholm, Sweden.
Physical Review Letters
|December 23, 2022
Summary
We explored terahertz magnetic field effects on cobalt thin films. The angular momentum relaxation time governs spin dynamics, showing a link to magnetic anisotropy.
Area of Science:
- Solid State Physics
- Materials Science
- Ultrafast Magnetism
Background:
- Terahertz (THz) magnetic fields offer precise control over ultrafast spin dynamics.
- Understanding spin dynamics in magnetic thin films is crucial for advanced technologies.
Purpose of the Study:
- To investigate spin dynamics induced by THz magnetic fields in epitaxial cobalt thin films across three crystalline phases.
- To elucidate the role of magnetic inertia and material parameters in THz-driven magnetization precession and oscillations.
Main Methods:
- Experimental measurements of spin dynamics in cobalt thin films subjected to THz magnetic fields.
- Solving the inertial Landau-Lifshitz-Gilbert equation to model experimental observations.
- Applying relativistic theory of magnetic inertia to identify key material parameters.
Main Results:
- THz magnetic fields induce magnetization precession with a subpicosecond lag.
- Magnetization exhibits damped THz oscillations at phase-dependent frequencies.
- The angular momentum relaxation time (η) is identified as the sole critical parameter for describing the observed dynamics.
- A direct proportionality between η and magnetocrystalline anisotropy strength is suggested.
Conclusions:
- The angular momentum relaxation time is a key determinant of THz-driven spin dynamics in cobalt.
- Magnetic inertia plays a significant role in the ultrafast precession response.
- Experimental findings are consistently explained by the inertial Landau-Lifshitz-Gilbert equation and relativistic magnetic inertia theory.
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