Reviewed by Lexie CornerJan 20 2025
Researchers at Tokyo Metropolitan University have discovered a novel superconducting material by synthesizing a new transition metal zirconide with varying iron-to-nickel ratios. The study was published in the Journal of Alloys and Compounds.
(a) Crystal structure of the team’s new material. (b) The lengths of repeating unit cells (lattice constants) as a function of iron to nickel ratio. (c) Transition temperatures as a function of iron to nickel ratio for magnetization, specific heat, and resistivity, all of which show the same dome-like shape. Image Credit: Tokyo Metropolitan University
Although iron zirconide and nickel zirconide are not superconducting, their newly created mixtures exhibit superconductivity, with a "dome-shaped" phase diagram characteristic of unconventional superconductors. This work offers a potential pathway for developing high-temperature superconducting materials with broader applications.
Superconductors are used in technologies such as power transmission cables, medical device magnets, and maglev systems. However, their widespread adoption is limited by the need to cool them to around 4 K. Materials exhibiting zero resistivity at higher temperatures, particularly near the 77 K threshold, would allow for cooling with liquid nitrogen instead of liquid helium, making the technology more accessible.
Recent discoveries, including iron-based superconductors identified in 2008, suggest that high-temperature superconductivity may operate through mechanisms distinct from those of conventional superconductors, such as those described by the Bardeen-Cooper-Schrieffer (BCS) theory. Materials with magnetic components or magnetic ordering are increasingly recognized as important for unconventional superconductivity.
A team from Tokyo Metropolitan University, led by Associate Professor Yoshikazu Mizuguchi, has developed a novel superconducting alloy containing iron, nickel, and zirconium. The team demonstrated its superconducting properties for the first time.
Using arc melting, the researchers combined iron, nickel, and zirconium in varying ratios, confirming that the alloy’s crystal structure matches that of tetragonal transition-metal zirconides, a family of promising superconducting materials. They observed that the lattice constants varied smoothly with the iron-to-nickel ratio. They identified a composition range where the superconducting transition temperature increased and then decreased, forming the characteristic "dome-like" phase diagram.
Additional magnetization experiments revealed an anomaly in nickel zirconide linked to a magnetic transition, highlighting a possible connection between magnetic ordering and the observed unconventional superconductivity.
The team hopes their findings will advance understanding of unconventional superconductivity and inspire the development of materials for next-generation superconducting devices.
The study was supported by JSPS-KAKENHI Grant Number 23KK0088, a TMU Research Project for an Emergent Future Society, and a Tokyo Government Advanced Research Grant (H31–1).
Journal Reference:
Shimada, R., et al. (2025) Superconducting properties and electronic structure of CuAl2-type transition-metal zirconide Fe1-xNixZr2. Journal of Alloys and Compounds. doi.org/10.1016/j.jallcom.2024.177442