Imaging of spin waves in atomically designed nanomagnets.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Spin dynamics in ferromagnetic materials involve collective phenomena like spin waves and domain walls.
• Atomic-scale interactions, including exchange interactions and magnetic anisotropy, govern these dynamics.
• Conventional probing methods lack atomic spatial resolution.

Purpose of the Study:

• To directly image standing spin waves in individual chains of iron atoms with atomic resolution.
• To map spin dynamics in engineered nanomagnets.
• To understand the atomic-scale mechanisms of magnetization switching.

Main Methods:

• Assembly of individual ferromagnetic iron atom chains on a Cu(2)N surface using a scanning tunnelling microscope (STM).
• Atom-to-atom probing of spin wave excitation amplitudes via inelastic electron tunnelling spectroscopy.
• Observation of stochastic magnetization switching dynamics influenced by STM tip position.

Main Results:

• Direct imaging of standing spin waves in individual S=2 Fe atom chains.
• Atomic-resolution mapping of spin wave amplitudes and their spatial variations.
• Correlation of magnetization switching rates with spin wave states and domain wall motion.

Conclusions:

• The study demonstrates atomic-scale imaging of spin dynamics in engineered nanomagnets.
• Spin wave excited states initiating at chain edges precede domain wall motion during magnetization switching.
• This approach enables future atomic-scale imaging of exotic spin excitations.