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Switching magnetization by the ultrafast Barnett effect

More than a century ago, Samuel Barnett discovered that mechanical rotation can give birth to magnetization. A consortium of researchers from FELIX Laboratory, Institute for Molecules and Materials, Poland and Japan have now found that this effect can actually be used to switch magnetization in a magnetic nanolayer, through exciting chiral vibrations of the lattice in the underlying substrate. Their results have been published in Nature.

The angular momentum of electrons gives rise to magnetization. More than a century ago, Barnett demonstrated that a rod - with otherwise zero net magnetization - gains a magnetic moment when mechanically spinning. A few years ago, scientists proved that lattice vibrations can be intrinsically chiral i.e. they can carry angular momentum. Thus, do such lattice vibrations also create magnetization? And can this be used for good?

The ultrafast Barnett effect and magnetic switching

Many scientists around the world are studying how to switch magnetization more efficiently, since data centers – which rely on switching magnetic bits to store and record information - are consuming a frighteningly large amount of energy. With this in mind, the team led by Professor Andrei Kirilyuk devised a creative approach to switch magnetization, based on the ultrafast analogue of the Barnett effect. Carl Davies, first-author of the publication, explains: “using infrared pulses of light from the free-electron lasers at FELIX, we drive circular vibrations of the lattice in glass or sapphire substrates. The substrate then becomes magnetic for a few trillionths of a second, flipping the magnetization of a thin layer mounted on top of it. The central role of the chiral phonons is revealed by the fact that the magnetic layer displayed switching only if specific lattice vibrations within in the underlying substrate are targeted.” 

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New frontier of research

This discovery shows how we can use lattice vibrations not only to magnetize ordinary glass or sapphire, but also to permanently switch magnetic order in nearby materials. This could provide a basis for many novel concepts in ultrafast opto-spintronics.


Phononic switching of magnetization by the ultrafast Barnett effect” Nature (2024). 

C.S. Davies, F.G.N. Fennema, A. Tsukamoto, I. Razdolski, A. Kimel and A. Kirilyuk