When a manganese crystal is cooled, its atoms start vibrating in sync with the magnetic order, like strings that tighten when neighboring little magnets align. A laser beam reflected off such a crystal changes color, and from that shift you can hear how the magnetic order plucks the atomic lattice.
In two very similar crystals — Mn4Nb2O9 and Mn4Ta2O9—the researchers noticed that atomic vibrations change already at 223 kelvins (about -50°C), when magnetic order is just beginning to emerge. And at full magnetic ordering (120 K and 110 K), some vibrations shift sharply in frequency. This is a sign that the crystal lattice has become slightly skewed, like a wooden frame warped by dampness.
Comparing the manganese crystals with cobalt ones, the authors saw that in manganese the lattice is more distorted, even though the band gaps (energy gaps for electrons) are nearly the same. This means the link between magnetism and electricity depends not only on atomic size but also on how their electron clouds overlap. Such materials could be useful in sensors where a magnetic field is converted into an electrical signal.
A temperature of 223 K is about -50°C, like a frosty night in Yakutia. At that temperature, the crystal already begins magnetic 'whispering,' though full order only sets in at -163°C.