Origin of Griffiths phase and long-range ordering in three-dimensional Nd0.8Sr0.2MnO 3 manganite perovskite

We report a systematical investigation of the structural and magnetic properties of three dimensional Nd 0.8 Sr 0.2 MnO 3 (NSMO-0.2) through a combination of experimental and theoretical analysis. This work demonstrates the crucial role of structural parameters including Mn − O bond length, < Mn − O − Mn > bond angle and octahedra rotation angle ( θ ) in determining the magnetic properties in one of the layered perovskite material, which we think is relevant to other materials that are comparable. We show Griffiths phase (GP) in NSMO-0.2, characterized by the presence of ferromagnetic spin correlations above the Curie temperature ( T c ) in the absence of spontaneous magnetization. Although, the GP has been previously reported in Nd 1 − x Sr x MnO 3 systems but its microscopic origin has remained unresolved. Our analysis strongly suggest that the GP in NSMO-0.2 originates from the local lattice distortion associated with Jahn–Teller (JT)-active Mn 3 + ions. The critical analysis of NSMO-0.2 around the T c ≈ 145.54 K gives the scaling exponents β = 0.486 ± 0.010, γ = 0.931 ± 0.008 and δ = 2.95 ± 0.05, which are close to the prediction of mean-field (MF) theory. Despite the slight deviations, the renormalization group analysis supports the presence of long-range magnetic ordering in the system, and the observed critical behavior can be described as a MF behavior. The deviation in the exponents from ideal MF values may be attributed to the complex magnetic ordering due to GP with inherent disorder and frustration.