Inverse NMR echo in the rotating coordinate frame in cobalt micropowders and nanowires

The first observation of an inverse nuclear magnetic resonance (NMR) echo in the laboratory coordinate system was recorded in cobalt nanofilms utilizing a nanosecond-scale magnetic video-pulse. This study extends that work by investigating a similar phenomenon, this time within the rotating coordinate frame in cobalt micropowders and nanowires. The nuclear spin system’s response within the domain walls of these cobalt structures was analyzed under the combined influence of radio-frequency (RF) fields and a microsecond magnetic video-pulse. As a result, an echo signal analogous to an inversion echo in a rotating coordinate system was produced. The amplitude of the magnetic video-pulse required to generate this echo signal serves as an estimate of the domain wall pinning strength in the micropowders and nanowires. Additionally, this paper discusses the unique electroless synthesis method for cobalt nanowires within an external magnetic field utilized in this research. The experimental findings on domain wall pinning forces in these systems are presented, with potential applications including advances in logic and memory devices, sensors, rare earth magnets, medical hyperthermia, and beyond.