ESRF News June 2026

June 2026 ESRFnews

METALLIC GLASSES

stable structure ( Sci . Adv . 11 eadz7406 ) . One might

have expected pressure to simply make the glass denser

– instead , the effect depended on the dominant mode

of relaxation . “ Our results clarified many controversies

in the literature , ” says Ruta .

Using a similar approach , Ruta and colleagues then

examined how these pressure - treated glasses recover on

reheating in the absence of any mechanical constraints .

In the conventional picture , alpha - relaxation should

restore the material to an equilibrium liquid , and erase

its history . Instead , the team found that this recovery is

incomplete : the glass retains a memory of the pressure

treatment , even after being reheated above the glass

transition , implying the existence of yet another slower

relaxation process controlling the devitrification

Figure 2 Mater Today 92 304 This was extremely

surprising says Ruta The loss of history upon

equilibration is a paradigm of glass physics

Many techniques

Ruta and her collaborators are not the only ones

challenging received wisdom in glass physics Other

ESRF users are tackling glass from multiple angles

from high pressure X ray absorption at beamlines such

as ID15A and BM23 to nuclear resonance and inelastic

scattering at ID14 An analysis of nuclear resonance data

taken at the ESRF s former ID18 beamline for instance

RETHINKING ALPHA AND BETA RELAXATION

In glass physics , alpha and beta relaxation are usually believed to be

distinct mechanisms – the former slow and over greater lengths , the latter

fast and over smaller lengths . But experiments at the ESRF ’ s former ID18

beamline led by Federico Caporaletti at the Université Libre de Bruxelles

show this might not be true .

Using time - domain interferometry – a technique based on nuclear -

resonance X - ray scattering – the researchers could capture a subset of

beta relaxation , Johari – Goldstein relaxation , and show that it is part of a

broader process that ultimately leads to structural rearrangement . In the

new picture , Johari – Goldstein beta relaxation acts as a precursor to alpha

relaxation , helping to destabilise the atomic cages that must be broken for

the glass to f low . The f indings suggest that glass relaxation may be more

unif ied than previously thought .

Besides its importance for the understanding of glass relaxation , the

work highlights the growing potential of time - domain interferometry , which

has been steadily developed since its introduction 15 years ago . The

technique currently probes a unique window of molecular motion , but its

ef f iciency could increase dramatically with new detector technologies .

100

P o t e n t i a l e n e r g y

liquid

dynamics

– 11K

– 7K

1 atm

GPa

( s )

1 . 86 1 . 88 1 . 90

1000 / T ( K

– 1

)

1 . 92 1 . 94 1 . 96 1 . 98 2 . 00

530 535 525 520

T ( K )

515 510 505 500

< 0

Coordinates

HPA

1 atm , HT

sample

Lorem

FIGURE 2 : GLASS DOESN ’ T FORGET

Structural relaxation time ( τ

) as a function of

temperature for metallic glasses prepared under

different pressures . Higher values correspond to

slower , more solid - like dynamics . In the conventional

picture , reheating above the glass transition

temperature ( Tg ) should erase any memory of

preparation , and all datasets would collapse onto a

single line . Instead , the clear separation between the

curves shows that the glass retains a memory of its

history , with relaxation remaining faster or slower

depending on how it was formed .

questions whether alpha and beta relaxation really are

separate mechanisms ( see “ Rethinking alpha and beta

relaxation ” , above left ) .

Meanwhile , the work of Ruta ’ s group suggests that it

should be possible to tune metallic glasses for different

applications , ranging from medical implants to

sports equipment and to consumer electronics . More

disordered glasses are likely to be more corrosion - and

fracture - resistant , whereas more ordered glasses will

have higher strength and stability . The results could

also be important in understanding the quality of

glassy materials produced by additive manufacture

Now she wants to expand her work to other more

complex types of glasses This will be difficult she

says but the X ray techniques particularly XPCS

are improving all the time I want to see if these

mechanisms are universal she says We didn t have

these technical capabilities for XPCS before EBS

we didn t have the resolution But I m always working

at the limits I want to go faster to get smaller length

scales There are plenty more things that should

be seen



Jon Cartwright

M A T E R . T O D A Y 9 2 3 0 4 / C C B Y 4 . 0

“ It should be possible to tune

metallic glasses for different

applications , ranging from medical

implants to sports equipment and to

consumer electronics ”