Ultra-high spin emission from antiferromagnetic FeRh

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• Antiferromagnets can generate spin currents when time-reversal symmetry is broken, often via magnetic fields or optical pumping.
• Understanding ultrafast spin dynamics in magnetic materials is crucial for developing next-generation electronic devices.

Purpose of the Study:

• To investigate picosecond spin pumping in metallic FeRh using optical pump-THz emission spectroscopy.
• To explore the influence of temperature on spin current generation in the antiferromagnetic phase of FeRh.

Main Methods:

• Optical pump-THz emission spectroscopy was employed to study spin pumping dynamics.
• Temperature and magnetic field-dependent measurements were combined with atomistic spin dynamics simulations.
• The role of conduction electrons in spin-biasing and spin accumulation was analyzed.

Main Results:

• A large and coherent spin pumping was observed in the low-temperature antiferromagnetic phase of FeRh, without transitioning to the ferromagnetic phase.
• Optical pumping and picosecond spin-biasing destabilized the antiferromagnetic spin-lattice, leading to spin accumulation.
• The high spin susceptibility of Rh atoms was identified as a key factor for the observed effect's amplitude.

Conclusions:

• The study demonstrates a novel mechanism for generating spin currents in antiferromagnetic FeRh.
• The findings suggest FeRh's potential as an efficient spin current emitter.
• Results corroborate the picosecond timescale of magnetic phase transitions, often obscured by slower dynamics.