Controllable giant itinerant negative spin polarization in superconducting high entropy alloy NbTaTiZrFe

Date

Oct 18, 2024

Time

1:00 PM - 2:00 PM

Speaker

Prof. Jong-Soo Rhyee

Affiliation

Kyung Hee University, Korea

Language

en

Main Topic

Materialien

Host

Martina Javorka

Description

Diamagnetism expels external magnetic fields due to the orbital motion of electrons (orbital diamagnetism) or the Meissner effect in superconductors. The magnetic susceptibility of orbital diamagnetism is generally very small within the order of 10-6 to 10-4 emu cm-3 Oe-1 because the orbital diamagnetism originates from the 2nd-order perturbation of atomic Hamiltonian in fully occupied orbitals. Here, we report the unprecedented discovery of spontaneously aligned giant itinerant negative spin-polarization (G-INSP) in the Fe-based high entropy alloy NbTaTiZrFe superconductor, synthesized by a powder metallurgical method. This compound exhibits a pronounced diamagnetic response below 42 K, and it reaches up to -60 % of diamagnetic external field shielding at the above superconducting transition temperature (Tc) of 6 K in zero-field-cooled conditions, transitioning to ferromagnetic behavior under field-cooled conditions. The extensive experimental and theoretical analysis suggests the itinerant negative spin polarization (INSP) including from substantial diamagnetic signal at low magnetic fields paired with a strong ferromagnetic coercive force (Hcoer = 1800 Oe), a ferromagnetic spin flip signal exclusive to the diamagnetic state, and metallic diamagnetism verified by scanning magnetic force microscopy and spin-resolved density functional theory calculation. The G-INSP originated from the strong antiparallel correlation between Fe spins and the other spins of diamagnetic elements. The coexistence of G-INSP and stable superconductivity strongly implies the possibility of S_z=-1 type spin-triplet superconductivity, which can be a promising platform for exploring Majorana fermions and their potential applications in quantum computation.

Links

• Seminars at the IFW

Last modified: Oct 18, 2024, 7:39:03 AM