Eur. Phys. J. B 12, 13-15 (1999)
https://doi.org/10.1007/s100510050969

Electron spin resonance and magnetic susceptibility suggest superconductivity in Na doped WO₃ samples

¹ Physik-Institut der Universität Zürich, 8057 Zürich, Switzerland
² Department of Materials and Interfaces, The Weizmann Institute of Science, Rehovot 76100, Israel

Corresponding author: ^a salex@physik-rzu.unizh.ch

Received: 14 April 1999
Revised: 6 September 1999
Published online: 15 November 1999

Abstract

In WO₃ doped with Na (WO₃:Na) an Electron Spin Resonance (ESR) signal with unresolved fine and/or hyperfine structure is detected and used as a probe for the state of the carriers. Using the saturation method we determined the spin-lattice relaxation rate of these paramagnetic centers. Upon cooling below 100 K, decreases markedly, as known to occur in NMR when a gap opens in the superconducting state. At low temperatures, quantitatively follows BCS behavior with a gap K or 2. The magnetic susceptibility exhibits a strong difference between magnetic-field cooled and zero-field cooled regimes below T_c which also supports a so far unknown superconducting phase resulting from Na doping.