Itinerant Electron Ferromagnetism in Y₄Co₃–⁵⁹Co NMR

The 59 Co NMR experiment has been performed in the normal state of Y 4 Co 3 , a new type of magnetic superconductor. The spin echo spectrum at a constant frequency (53 MHz) consists of three kinds of resonance signals corresponding to the three crystallographically inequivalent Co sites. Only one of these sites shows the large negative Knight shift and identified as Co-2b sites which form a linear chain along the c -axis. The zero field ferromagnetic nuclear resonance has been also observed around 18 MHz with the half width of 9 MHz at 2.1 K, which gives the ferromagnetic moment of 0.23 µ B , indicating the weak itinerant ferromagnetism in this compound.