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NEWS

December 2025 ESRFnews

Scientists have uncovered how

relaxation processes in metallic glasses

behave under extreme conditions,

opening the door to designing these

materials with tailored properties.

Metallic glasses combine the

strength of metals with the disorder

of glass, giving them elasticity,

corrosion resistance and unusual

electronic and magnetic properties.

But their performance depends on the

conditions under which they form, and

how their atoms move or relax – much

of which is unknown.

Relaxation comes in two forms:

slow, cooperative α-relaxation,

which governs how a glass flows and

ages, and faster, local β-relaxation,

which persists even below the glass

transition temperature. The scientists

combined in situ and ex situ high-

pressure experimental techniques with

fast-scan calorimetry and synchrotron

X-ray diffraction at the ESRF’s ID13

and ID15A beamlines. “We wanted

to test the belief that high pressure

always makes materials denser

and more stable,” says Jie Shen,

a co-corresponding author at the

Institut Néel.

The team identified two distinct

mechanisms. Under β-relaxation,

compression reduces atomic

mobility and enhances disorder

without changing density. Meanwhile,

under α-relaxation, pressure drives

a structural ordering that improves

thermal stability. Strikingly, the switch

between regimes always occurs at the

same relative temperature compared

with the glass transition, regardless of

the pressure (Sci. Adv. 11 eadz7406).

“We can now separate the effects

of structure and relaxation on glass

stability,” says Beatrice Ruta (below)

at the CNRS Institut Néel, and an

ESRF visiting scientist. “This opens

the doors to designing glasses with

specific properties, by carefully

controlling heat and pressure

Relaxation mapped in

metallic glass

Using high-pressure X-ray diffraction

at the ESRF’s ID15B, ID11 and ID27

beamlines, researchers have discovered

a metal that combines electrical

conductivity with polarity, enabling

it to double the frequency of light –

an optical effect usually reserved for

non-metals.

In ordinary metals, conduction

electrons are donated by the metal

atoms. However, the new compound,

magnesium chloride (Mg₃Cl₇), is

an anionic metal, which means that

conduction arises through electrons

donated by the chlorine ions. This

unusual mechanism weakens the

normal electrical screening in metals

and allows the crystal to retain a

permanent internal separation of

charge

But MgCl does more than just

conduct When illuminated it

emits light at twice the incoming

frequency a phenomenon known

as second harmonic generation J

Am Chem Soc 147 32591 The rare

coexistence of metallicity polarity and

frequencydoubling optics in a single

material points to opportunities in

future electronics, sensors and energy

technologies, the researchers say.

“It’s very exciting that we’ve

discovered a metal that not only

conducts electricity but also emits

light in unexpected ways,” says Yuqing

Yin (above), the first author of the

study who is based at the University

of Bayreuth in Germany. “This

combination is extremely unusual

in nature and offers completely new

perspectives for designing materials

with multifunctional properties.”

The crystal was stabilised

under the immense pressure of a

diamondanvil cell Thanks to

the enhanced brilliance of the EBS

source we were able to collect high

quality diffraction data from the

microcrystalline samples and solve

the structure says Yin

Coauthor Leonid Dubrovinsky

of the University of Bayreuth thinks

their studies are only at the beginning

This compound is unlikely to be made

on a large scale today but the principles

weve uncovered show us new ways

of thinking about chemistry and

materials design he says

E S R F

New metal def ies conventions

E S R F

“Thanks to

the enhanced

brilliance of the

EBS, we were

able to solve the

structure”