Effect of Ce substitution on the local magnetic ordering and phonon instabilities in antiferromagnetic DyCrO3 perovskites

Abstract

Abstract A detailed crystal structure analysis, temperature and field dependence of magnetic characteristics and phonon instabilities for different compositions (0.1 ⩽ x ⩽ 0.5) of Dy1−x Ce x CrO3 solid-solutions have been reported. All the investigated compounds exhibit distorted orthorhombic crystal structure with a distortion factor of d Oct/d Cell ∼ 6 × 10−3/3.5 ppm (for x ∼ 0.2) for Pbnm space group that follows Vegard’s law. The bonds between apical oxygen atoms (OA1) and Cr atoms stand more rigidly in comparison with the basal oxygen atoms (OB1/OB2) resulting the octahedral distortion and thereby causing the changes in phonon modes. The CrO6 octahedral tilt angle θ rotates with respect to the Miller pseudocubic axis [101] which varies from 10.36° (x = 0.1) to 12.25° (x = 0.5) and significantly influences the Ag(5) phonon stability by 3% for a change in A-site mean radius from 1.095 Å to 1.141 Å for x = 0.1 and 0.5, respectively. From the magnetization measurements we find that these series of compositions exhibit canted antiferromagnetic (AFM) ordering with Néel temperature, T N 1 that increases from 151.8 K (x = 0.1) to 162 K (x = 0.5) which also manifests as a significant reduction in the magneto-crystalline anisotropy (H K ∼ 2.58 kOe → 2.07 kOe, K 1 ∼ 36.47 J m−3 → 18.97 J m−3) while maintaining the stable Γ4(G x , A y , F z ) AFM configuration. Both Dzyaloshinskii–Moriya interaction method and modified Curie–Weiss law are employed to analyse the inverse paramagnetic susceptibility, χ −1(T > T N 1 ). Further, we have evaluated the symmetric (J S) and antisymmetric exchange (D AS) constants, which show progressively increasing trend (J S → 10.08 K to 11.18 K and D AS → 1.24 K to 1.73 K) with the incorporation of Ce inside the perovskite lattice. Furthermore, the role of Ce substitution on the low-temperature spin reorientation transition (T SR ∼ 3.5 K → 16.8 K pertaining to the Γ25 phase configuration) and emergence of Γ 2 ( F x , C y , G z ; F x R , C y R ) weak-FM phase between 31 K and 45.5 K are discussed in consonance with the phonon spectra.