The spin dynamics of the cluster‐glass Fe0.25Mg0.75TiO3 probed by the muon spin relaxation method

A cluster‐glass (CG) Fe_0.25Mg_0.75TiO₃ is investigated by muon spin relaxation measurements. It is found that the local magnetic fields at the muon stopping site are established at temperatures five times as high as the freezing temperature T_f. It is also found that the electron spins fluctuate even below T_f. The critical region around T_f in Fe_0.25Mg_0.75TiO₃ is extremely wide in contrast to that of ordinary spin‐glass (SG) systems. It is clearly demonstrated that the microscopic and dynamical properties of CG are remarkably different from those of SG. This revised version was published online in July 2006 with corrections to the Cover Date.     

Muon spin relaxation study on magnetism in high quality single crystal of a high transition temperature superconductor La2−xSrxCuO4−σ (0.11≤x≤0.14)

The positive muon spin relaxation method is applied to probe magnetic ordering in the superconducting phase of a high quality single crystal of La_2−xSr_xCuO_4−σ (0.11≤x≤0.14). The well characterized crystal ofx=0.11 (T _c=34.5 K) with nearly complete flux exclusion exhibits spin freezing at 8K(T _f) with significant spin fluctuation up to 20 K. The onset of spin fluctuation andT _f decrease against increasingx towardsx=0.15, suggesting an existence of a magnetic phase boundary aroundx whereT _c becomes maximum.