Seminarium Międzynarodowego Laboratorium Silnych Pól Magnetycznych i Niskich Temperatur PAN
ul. Gajowicka 95, sala seminaryjna (nowy budynek, II piętro)
Are new high temperature superconductors ready for novel magnet applications?
Prof. Akiyasu Yamamoto
Department of Applied Physics, Tokyo University of Agriculture and Technology, Institute for Elemental Strategy, Tokyo Institute of Technology
The recently discovered high temperature superconductors (HTSs), Hydrogen sulfide (H3S)1, Fe-based superconductors (FBS)2 and magnesium diboride (MgB2)3, raised an exciting question “are there any other HTS or even RTS materials besides cuprates?” H3S recorded a surprisingly high transition temperature (Tc) of 203 K (–70 °C), which is above the lowest natural temperature on Earth (–89.2 °C or 184 K, Vostók Station in Antarctica), under a pressure of 150 GPa. Tc of both FBS (58 K) and MgB2 (39 K) well exceeds the so-called “BCS-limit (~30 K)” of the 20th century.
On the other hand, the discovery of new HTS always provokes huge interest for applications, since superconducting loss-less transmission and very high-field magnet are of great interest in fields of energy, medical, transport and high energy physics. Superconductors with persistent zero-resistance currents can serve as permanent magnets for high-field applications requiring a strong and stable magnetic field, such as magnetic resonance imaging (MRI). In this seminar, we introducethat new 40-K-class metallic HTSs (FBS and MgB2) make an excellent permanent bulk magnet 4,5. The magnetic field trapped in this magnet is uniformly distributed, as for single-crystalline neodymium-iron-boron, and extremely stable (with decay late less than 0.1 ppm/h). Because MgB2 and some of FBSs are simple binary/ternary compounds without rare-earth metals, polycrystalline bulk material can be industrially fabricated at low cost and with high yield to serve as strong magnets that are compatible with conventional compact cryocoolers, making new HTS bulks promising for the next generation of Tesla-class permanent-magnet applications.
[1] A. Drozdov, M. Eremets, I. Troyan, V. Ksenofontov, S. Shylin,“Conventional superconductivity at 203 K at high pressures in the sulfur hydride system, Nature 525, 73 (2015).
[2] Y. Kamihara, T. Watanabe, M. Hirano, H. Hosono,“Iron-Based Layered Superconductor La[O1-xFx]FeAs (x = 0.05−0.12) with Tc = 26 K, J. Am. Chem. Soc., 130, 3296 (2008).
[3] J. Nagamatsu, N. Nakagawa, T. Muranaka, Y. Zenitani, J. Akimitsu, “Superconductivity at 39 K in magnesium diboride, Nature 410, 63 (2001).
[4] J. D. Weiss, A. Yamamoto, A. A. Polyanskii, R. B. Richardson, D. C. Larbalestier, E. E. Hellstrom,“Demonstration of an iron-pnictide bulk superconducting magnet capable of trapping over 1 T, Supercond. Sci. Technol.– Fast Track Communication 28, 112001 (2015).
[5] A. Yamamoto, A. Ishihara, M. Tomita, K. Kishio, “Permanent magnet with MgB2 bulk superconductor, Appl. Phys. Lett. 105, 032601 (2014).
