On the possibility of nuclear self-spin-locking in ferromagnets

Abstract

Abstract Nuclear spin systems in ferromagnets and antiferromagnets can bend the electronic magnetization, via their hyperfine interaction, so as to produce an apparent magnetic field that is proportional to the transverse nuclear spin magnetization and parallel to it. A nuclear spin system in any solid can also be ‘spin-locked’ by application of a resonant r.f. field along a transverse nuclear magnetization, and transverse spin relaxation is then prevented by the r.f. field. In this Article we combine these ideas and conclude that nuclear spin systems in (anti)ferromagnets might be placed in a transient self-locked state. The plausibility criterion for observation of self-locking is shown to be that the apparent field produced by the maximum nuclear magnetism be larger than the ordinary NMR linewidth. A simple treatment of the coupled electron-nuclear resonance frequency shift is given for the case of small or large tilt of the nuclear magnetization, and we show that if the small-tilt shift is greater than the NMR linewidth, self-locking might be attainable. There is an analogy between the self-locked state, and the random-phase representation of the BCS superconductor provided by Anderson. The self-locked state might be observed by looking for a longT2decay after a suitably chosen preparation.