  Exchange bias (EB) as large as ~5.5 kOe is observed in SrLaCo0.5Mn0.5O4 which
is the highest ever found in any layered transition metal oxides including
Ruddlesden-Popper series. Neutron diffraction measurement rules out long-range
magnetic ordering and together with dc magnetic measurements suggest formation
of short-range magnetic domains. AC magnetic susceptibility, magnetic memory
effect and magnetic training effect confirm the system to be a cluster spin
glass. By carrying out density functional calculations on several model
configurations, we propose that EB is originated at the boundary between
Mn-rich antiferromagnetic and Co-rich ferromagnetic domains at the
sub-nanoscale. Reversal of magnetization axis on the Co-side alters the
magnetic coupling between the interfacial Mn and Co spins which leads to EB.
Our analysis infers that the presence of competing magnetic interactions is
sufficient to induce exchange bias and thereby a wide range of materials
exhibiting giant EB can be engineered for designing novel magnetic memory
devices.
