Giant exchange bias in the single-layered Ruddlesden-Popper perovskite SrLaCo0.5Mn0.5O4

Exchange bias (EB) as large as \ensuremath{\sim}5.5 kOe is observed in $\mathrm{SrLaC}{\mathrm{o}}_{0.5}\mathrm{M}{\mathrm{n}}_{0.5}{\mathrm{O}}_{4}$, 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 suggests 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 subnanoscale. 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.