Giant exchange bias, non-Griffith clustering, and re-entrant cluster glass freezing in mixed-valent disordered Pr1.5Sr0.5CoFeO6

With exceptional structural tunability, double perovskites serve as a versatile platform to explore diverse magnetic phenomena. Here, we investigate the magnetic properties of disordered Pr1.5Sr0.5CoFeO6. DC magnetization measurements unveil an antiferromagnetic (AFM) ground state with a Néel temperature TN ∼ 147 K. The persistence of magnetic irreversibility in the temperature range of 147–185 K indicates the presence of non-Griffiths type ferromagnetic (FM) clusters nestled within a paramagnetic host. AC susceptibility measurements [both χ′(T) and χ″(T)] reconfirm long-range AFM ordering at ∼147 K and reveal a re-entrant cluster glass (CG) state below Tf ∼ 31.35 K, characterized by zν = 0.73 ± 0.07 and τ0 = (3.6 ± 0.9) × 10−5 s. Strikingly, the realization of a giant exchange bias (EB) effect with an exchange bias field of |HEB| ∼ 6.6 kOe at 5 K under a cooling field of HCF = 60 kOe suggests robust intercluster pinning among AFM–CG–FM interfaces. Furthermore, a rare spontaneous EB of |HEB| ∼ 1640 Oe observed at 5 K highlights the intrinsic nature of the unidirectional magnetic anisotropy present in the system. The training effect exhibits an ∼18% reduction in HEB, indicating the relaxation of metastable interfacial spins toward equilibrium. The underlying spin dynamics have been further analyzed in terms of rotatable and frozen spin components each characterized by distinct relaxation times. The insights gained from this investigation offer a framework for rational design and understanding exchange bias phenomena.