Effect of Ce substitution on the local magnetic ordering and phonon instabilities in antiferromagnetic DyCrO 3 perovskites.

A detailed crystal structure analysis, temperature and field dependence of magnetic characteristics and phonon instabilities for different compositions (0.1 ⩽ x ⩽ 0.5) of Dy 1- x Ce x CrO 3 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 (O A1 ) and Cr atoms stand more rigidly in comparison with the basal oxygen atoms (O B1 /O B2 ) resulting the octahedral distortion and thereby causing the changes in phonon modes. The CrO 6 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 A g (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,TN1that 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 Γ 4 ( 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 >TN1). 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 Γ 25 phase configuration) and emergence ofΓ2(Fx,Cy,Gz;FxR,CyR)weak-FM phase between 31 K and 45.5 K are discussed in consonance with the phonon spectra.