We demonstrate precise control of exchange bias (EB) in the Nd_2−xSr_xCoMnO_6−δ (0 ⩽ x ⩽ 1) double-perovskite series through Sr²⁺-induced hole doping, revealing a remarkable transition between normal and inverse EB. Using neutron powder diffraction and x-ray absorption spectroscopy, we uncover a structural evolution from a B-site-ordered monoclinic (P2₁/n) to a disordered rhombohedral (R3c) phase with increasing x. This transition is accompanied by a shift in the effective Co valence from +2 toward +3, while the Mn valence remains close to +3.6 throughout the series. DC magnetization measurements indicate a gradual suppression of ferromagnetism with hole doping, whereas ac magnetization measurements for x = 0.75 reveal pronounced cluster-glass behavior. Notably, x = 0.75 also exhibits the highest EB field of ∼4 kOe at 8 K under a 20 kOe cooling field. After correcting for minor-loop effects, we identify robust inverse EB at x = 0.75, persisting even under a 60 kOe cooling field. The coexistence of pronounced glassiness with large EB fields and robust inverse EB suggests that interfacial interactions involving frustrated spins play a central role in stabilizing these exotic EB states. Furthermore, the apparent nonmonotonic evolution of the measured EB with doping is found to be largely influenced by minor-loop effects. After correcting for these effects, the intrinsic EB exhibits an overall reduction with increasing doping and antisite disorder. Interestingly, the intrinsic EB displays a local maximum when the ferromagnetic and nonferromagnetic phase fractions become comparable, despite the persistence of strong glassy dynamics across the series. These findings establish rare-earth double perovskites as a promising platform for engineering tunable EB functionalities through controlled structural disorder and magnetic phase competition, opening new avenues for advanced spintronic and magnetic memory applications.

We report a comprehensive investigation of the structural and magnetic properties of Mn-substituted Fe₂TiSn Heusler alloy using powder neutron diffraction and magnetization measurements. Rietveld refinement of neutron diffraction confirms the cubic L2₁ structure with ∼9% B2-type antisite disorder between Fe and Ti/Mn sites. Magnetization measured as a function of temperature and magnetic field reveal the emergence of short-range ferromagnetic correlations below 325 K, arising from nanoscale ∼9.04 nm) ferromagnetic clusters. At high temperatures, these clusters exhibit superparamagnetic behavior, but on cooling, enhanced inter-cluster interactions drive a crossover to a correlated ferromagnetic-like state. The progression from superparamagnetism to interacting-cluster state correlates with antisite disorder and local lattice distortion, which tune both the cluster dimensions and its coupling strength. The results highlight the critical role of structural disorder in governing magnetic cluster dynamics in Fe-based Heusler alloys and establish a pathway to engineer collective spin states for spintronic and magnetic storage applications.

The structural, thermodynamic, and magnetic properties of Na₂CrCl₄ have been investigated to provide fundamental insights into this ternary halide relevant to chloride-based molten salt reactor systems. Room-temperature powder X-ray and neutron diffraction confirm a monoclinic (P2₁/c) structure and phase purity. Neutron diffraction measurements at 4.6 K reveal additional magnetic reflections indexed with (Formula presented), indicating the onset of long-range antiferromagnetic order. Low-temperature heat capacity measurements in the range 2–300 K show a pronounced λ-type anomaly at T_N = 8.5 ± 0.5 K, with an associated magnetic entropy S_mag = 11.9 ± 0.4 J K^–1 mol ^–1 consistent with antiferromagnetic ordering of high-spin Cr²⁺ (S = 2), a second-order phase transition. The standard molar entropy at 298.15 K, S_m^°(298.15 K) = 256.8 ± 7.7 J K^–1 mol ^–1, is slightly lower than previous CALPHAD assessments of the NaCl-CrCl₂ system. Magnetic susceptibility measurements also confirm antiferromagnetic behavior, with a Curie–Weiss fit giving μ_eff = 5.57 ± 0.05 μ_B and θ_CW = −15.0 ± 1.0 K. Compared to the related ferromagnetic chlorides K₂CrCl₄, Rb₂CrCl₄, and Cs₂CrCl₄, Na₂CrCl₄ exhibits a distinctly lower ordering temperature and antiferromagnetic structure, likely due to variations in lattice geometry and exchange interactions. These results provide the first experimental thermodynamic parameters for Na₂CrCl₄, contributing to refining phase diagrams and corrosion models in chloride salt systems.