TOKYO — Researchers
from Tokyo Metropolitan University have discovered a new superconducting
material which can be more widely deployed in society.
They combined iron, nickel, and zirconium, to create a new
transition metal zirconide with different ratios of iron to nickel.
While both iron zirconide and nickel zirconide are not
superconducting, the newly prepared mixtures are, exhibiting a “dome-shaped”
phase diagram typical of so-called “unconventional superconductors,” a
promising avenue for developing high temperature superconducting materials,
according to the study published in the Journal of Alloys and Compounds.
Superconductors already play an active role in cutting-edge
technologies, from superconducting magnets in medical devices and maglev
systems to superconducting cables for power transmission.
However, they generally rely on cooling to temperatures of
around four Kelvin, a key roadblock in wider deployment of the technology.
Scientists are on the lookout for materials which can show
zero resistivity at higher temperatures, particularly the 77 Kelvin threshold
at which liquid nitrogen can be used to cool the materials instead of liquid
helium.
Now, a team of researchers led by Associate Professor
Yoshikazu Mizuguchi from Tokyo Metropolitan University have conceived a new
superconducting material containing a magnetic element.
For the first time, they showed that a polycrystalline alloy
of iron, nickel, and zirconium shows superconducting properties. Curiously,
both iron zirconide and nickel zirconide are not superconducting in crystalline
form.
According to the study, in experiments which began as an
undergraduate student project, the team combined iron, nickel, and zirconium in
different ratios using a method known as arc melting, confirming that the
resulting alloy had the same crystal structure as tetragonal transition-metal
zirconides, a family of promising superconducting materials.
The lattice constants, or the lengths of repeating cells,
were also found to change smoothly with the ratio of iron to nickel.
Crucially, they found a region of compositions where the
superconducting transition temperature rose, then fell again. This “dome-like”
form is a promising hallmark of unconventional superconductivity.
