Magnetic rare-earth ion mediated 4f-3d interlayer coupling and giant exchange bias in single layered Ruddlesden-Popper perovskites SrLnCo<inf>0.5</inf>Mn<inf>0.5</inf>O<inf>4</inf> (Ln = Pr, Nd)

We report an in-depth study on exotic magnetic nature including giant exchange bias in single layered Ruddlesden-Popper structure polycrystalline perovskites SrRCo0.5Mn0.5O4 (R = Pr, and Nd). X-ray diffraction, neutron diffraction, and Raman spectroscopic studies on both compounds confirm tetragonal crystal structure with I4/mmm space group. Temperature evolution of dc magnetization and ac susceptibility show multiple magnetic phase transitions in both the compounds, i.e., high temperature ferromagnetic transition (Tc = 178/172 K) followed by antiferromagnetic transition at an intermediate temperature (TN = 90/100 K) and finally entering to a glassy magnetic state at lower temperatures (Tg = 35/25 K). Neutron powder diffraction confirms the absence of long-range magnetic order in both compounds. Atomically disordered (Co/Mn)O2 layers give rise to intralayer short range 3d-3d magnetic interactions resulting in co-existence of ferromagnetic and antiferromagnetic regions producing frozen magnetic state below Tg. Present experimental results and analysis show giant exchange bias of − 3.6/− 1.7 kOe (Pr/Nd systems) under cooling field of 50 kOe at 5 K, which stems from the inherent magnetic inhomogeneity. Our results reveal that magnetic rare-earth ion (Pr/Nd) induces a pathway of interlayer 4f-3d magnetic interactions leading to antiferromagnetic interaction between adjacent (Co/Mn)O2 layers, and this has a significant influence on the exchange bias values at low temperature.