Radio-frequency spin resonance of positive muons in α-iron

Abstract Resonant transitions between the Zeeman levels of spin-polarized positive muons (μ+) implanted into iron foils have been observed at 1040 K by applying a 24·0 MHz transverse r.f. field and varying the longitudinal external magnetic field. The trapping of muons at small concentrations of crystal defects (about 10−7, i.e. of the order of magnitude of the thermal equilibrium concentration of vacancies) was detected and the local magnetic field at the traps determined.