Field-induced spin-state transition, critical exponents and non-equilibrium-memory effects in semi-spin-glass perovskite (LaNd)(CoMn)O₃

Abstract Efficient control of the structural, magnetic and electrical properties of Rare-earth (RE) based perovskites (ABO 3 ) is crucial for advanced spintronic applications and can be achieved by means of site-specific substitution. In this comprehensive study, we explore the role of (Nd) A-site and (Mn) B-site co-substitution on the physical properties of pristine LaCoO 3 perovskite. The resulting compound La 0.5 Nd 0.5 Co 0.5 Mn 0.5 O 3 (LNCMO) with an orthorhombic ( Pbnm ) crystal structure ( a = 5.4811(4) Å , b = 5.5074(4) Å and c = 7.7491(5) Å) exhibits a significantly reduced Jahn-Teller distortion (JT) compared to pristine LaCoO 3 with a monoclinic ( I2/a ) structure. The ac-magnetic susceptibility χ( T, f, H dc ) measurements and wait time dependence of the isothermal magnetization M(t) provide clear evidence for the re-entrant spin-glass-like behavior with freezing temperature T SG = 133 K below the ferrimagnetic Curie temperature ( T FiM ∼137.4 K). Additionally, the asymmetric response of magnetic relaxation in the system to positive and negative temperature cycling well below the freezing temperature has been explained by means of the hierarchical model. Furthermore, a giant coercivity ( H C ∼14 kOe) and remanence ( M R ∼ 6440 emu mol −1 ) with weak loop-asymmetry indicates the presence of large magnetic anisotropy in LNCMO, evidenced by a high magneto-crystalline anisotropy field ( H K ∼ 80 kOe) and anisotropy constant ( K 1 ∼ 1.45 × 10 7 erg cm −3 ). The unique electronic structure of trivalent Nd (5 f 3 ) and mixed valent Mn (3 d 4 /3 d 3 ) with spin-orbit coupling energies 4 eV and 11.43 eV/10.51 eV, respectively and competing exchange interaction (∼0.67 meV) between Mn and Co cations in different pathways results in enhanced magnetic-order parameters. Moreover, the co-substitution results to a pseudo-first order like state close to the spin-state transition H * of Co (S = 0 → 2) which has been verified by the modified Arrott plot analysis yielding critical exponents β = 0.67, γ = 1.44 and δ = 3.13. A field-induced metamagnetic transition H T emerges in the range 30 K ⩽T⩽ 130 K which has been mapped along with other parameters resulting in a H-T phase diagram which clearly distinguishes various magnetic phases and sharp crossover between the different states providing a clear and vivid picture of the overall magnetic structure of LNCMO.