Future Hard Drives Accessible via Superfast Lasers

• Spin currents, a property of electron particles, represent angular momentum carried by the particle.
• Spin currents flow through a medium when electrons transmit a spin state in quick succession before reverting to their original state.
• Spin currents are crucial for data storage and retrieval in computer hard drives.

Spintronics and Future Drives
• Spintronics is a branch of physics that studies and manipulates electrons’ magnetic properties.
• Magnetic hard drives in computers already use spintronics, which allows for quick storage and reading of data encoded in the ups and downs of its electrons.
• The strength of the magnetic field over small parts of the disc changes the spin states, enhancing the drive’s read/write speed.

Spin Current Generation Efficiency
• Spin currents are expected to provide the next quantum leap on this frontier.
• The efficiency of spin current generation is critical for device applications.

Production of Spin Currents Directly
• Researchers are exploring ways to produce spin currents directly.
• One scheme involves firing lasers at a material, applying a magnetic field, and having electrons interact with impurities in the material.
• Another scheme involves sandwiching three layers of carefully chosen materials together, causing magnetisation changes that induce spin currents in the uppermost layer.
• These schemes have produced spin currents in the order of a few hundred femtoseconds, a “factor 1,000” improvement on other technologies.

Scientists Advance Spintronic Technology

• Scientists from Germany, Sweden, and the U.S. used a Heusler alloy to demonstrate spin transfer from one atom to another.
• The findings paved the way for spintronic devices operating on few-femtosecond or faster time scales.

‘Petahertz Clock Rates’
• Researchers from the Max Planck Institute for Microstructure Physics, Germany, used a new concept to produce spin currents in 2 fs.
• The concept was based on optical intersite spin transfer (OISTR), where light of specific frequencies could rapidly manipulate electrons’ angular momentum in a material.
• The mechanism was mediated by intervening processes, making it more complex to translate the energy in the wave to the electrons’ spin.

One-two punch
• Researchers engineered a material consisting of 20 alternating layers of cobalt and platinum.
• They applied a magnetic field perpendicular to the stack to force the electrons to settle into an ordered arrangement of spins.
• The researchers fired a pulse of linearly polarised light into the material and shot another pulse of circularly polarised light.
• The absorption of the circularly polarised light indicated that in the cobalt layers, the electrons’ spins had become around 10% less ordered, whereas they’d become slightly more ordered in the platinum layers within just 2 fs after the linearly polarised light had passed through.
• The team developed a mathematical model to explain these findings using density functional theory, which allows physicists to predict a material’s properties based on some fundamental quantum properties.