Evidence of intrinsic exchange bias and its origin in spin-glass-like disordered L0.5 Sr0.5 Mn O3 manganites (L=Y, Y0.5 Sm0.5, and Y0.5 La0.5)

Exchange-bias (EB) phenomena have been observed in the L0.5 Sr0.5 Mn O3 (L=Y, Y0.5 Sm0.5, and Y0.5 La0.5) -type manganites showing cluster-glass-like and spin-glass-like behavior. The field cooled magnetic hysteresis loops exhibit shifts both in the field and magnetization axes. The values of exchange field (HE), coercivity (HC), remanence asymmetry (ME), and magnetic coercivity (MC) of L0.5 Sr0.5 Mn O3 are found to depend strongly on temperature, measuring field, as well as strength of cooling field Hcool. HE increases sharply with the magnitude of Hcool (≤3 T), but for larger Hcool (>3 T), it decreases due to the growth of the ferromagnetic cluster size. This observed behavior has been explained in terms of interfacial exchange coupling between coexisting ferromagnetic cluster glass and the disordered spin-glass-like phases, where the spin configurations are strongly affected by the cooling field strength. Below the spin and/or cluster glass freezing temperature (Tf), both HE and ME decrease exponentially with temperature. The value of HC increases almost exponentially with increasing magnetic-field step size (ΔH). In addition, the observed training effect of the EB behavior has been explained well in terms of the existing relaxation model developed for other classical EB systems. In view of the use of manganites in spintronics, the present observation of EB-like shift even in the mixed valent polycrystalline manganites such as L0.5 Sr0.5 Mn O3 is of paramount importance.