Researchers used ultrashort laser pulse excitation to optically stimulate specific atomic vibrations of the magnet’s crystal lattice
From
the University of Lancaster
February
8, 2021 -- Fast and energy-efficient future data processing technologies are on
the horizon after an international team of scientists successfully manipulated
magnets at the atomic level.
Physicist
Dr Rostislav Mikhaylovskiy from Lancaster University
said: “With stalling efficiency trends of current technology, new scientific
approaches are especially valuable. Our discovery of the atomically-driven
ultrafast control of magnetism opens broad avenues for fast and
energy-efficient future data processing technologies essential to keep up with
our data hunger.”
Magnetic materials are heavily used in
modern life with applications ranging from fridge magnets to Google and
Amazon’s data centers used to store digital information.
These materials host trillions of
mutually aligned elementary magnetic moments or “spins”, whose alignment is
largely governed by the arrangement of the atoms in the crystal lattice.
The spin can be seen as an elementary
“needle of a compass”, typically depicted as an arrow showing the direction
from North to South poles. In magnets all spins are aligned along the same
direction by the force called exchange interaction. The exchange interaction is
one of the strongest quantum effects which is responsible for the very
existence of magnetic materials.
The ever-growing demand for efficient
magnetic data processing calls for novel means to manipulate the magnetic state
and manipulating the exchange interaction would be the most efficient and
ultimately fastest way to control magnetism.
To achieve this result, the researchers
used the fastest and the strongest stimulus available: ultrashort laser pulse
excitation. They used light to optically stimulate specific atomic vibrations
of the magnet’s crystal lattice which extensively disturbed and distorted the
structure of the material.
The results of this study are published
in the prestigious journal Nature
Materials by the international team from Lancaster, Delft, Nijmegen,
Liege and Kiev.
PhD student Jorrit Hortensius from the Technical
University of Delft said: “We optically shake the lattice of a magnet that is
made up of alternating up and down small magnetic moments and therefore does
not have a net magnetization, unlike the familiar fridge magnets.”
After shaking the crystal for a very
short period of time, the researchers measured how the magnetic properties
evolve directly in time. Following the shaking, the magnetic system of the anti-ferro-magnet
changes, such that a net magnetization appears: for a fraction of time the material
becomes similar to the everyday fridge magnets.
This all occurs within an
unprecedentedly short time of less than a few picoseconds (millionth of a
millionth of a second). This time is not only orders of magnitude shorter than
the recording time in modern computer hard drives, but also exactly matches the
fundamental limit for the magnetization switching.
Dr Rostislav Mikhaylovskiy from
Lancaster University explains: “It has long been thought that the control of
magnetism by atomic vibrations is restricted to acoustic excitations (sound
waves) and cannot be faster than nanoseconds. We have reduced the magnetic
switching time by 1000 times that is a major milestone in itself.”
Dr Dmytro Afanasiev from the Technical
University of Delft adds: “We believe that our findings will stimulate further
research into exploring and understanding the exact mechanisms governing the
ultrafast lattice control of the magnetic state.”
https://www.lancaster.ac.uk/news/scientists-manipulate-magnets-at-the-atomic-scale
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