Negative muon spin rotation and relaxation on superconducting MgB2

Abstract The internal nuclear magnetic field in a superconducting MgB 2 powder sample was studied with a µ − SR technique. Although the past µ + SR study on MgB 2 reported the appearance of a dynamic behavior even below T c due to µ + diffusion, µ − SR shows a static behavior in the whole temperature range measured, as expected. The ZF- µ − SR spectra do not suggest any appearance of additional magnetic field below T c within the experimental accuracy. Considering the small asymmetry of the µ − SR signal, it is a challenge to detect the appearance of an internal magnetic field below T c caused by the time reversal symmetry breaking.