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

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-xCexCrO3 solid-solutions have been reported. All the investigated compounds exhibit distorted orthorhombic crystal structure with a distortion factor of dOct/dCell ~ 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 and Cr atoms stand more rigidly in comparison with the basal oxygen atoms 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 AFM ordering with TN1 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 while maintaining the stable Γ4 AFM configuration. Dzyaloshinskii–Moriya interaction (DM) method and modified Curie-Weiss (CW) law are employed to analyze the χ-1(T >TN1). We have also evaluated the symmetric (JS) and antisymmetric exchange (DAS) constants, which show progressively increasing trend (JS → 10.08 to 11.18 K and DAS → 1.24 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 (TSR ~ 3.5 K → 16.8 K pertaining to the Γ25 phase configuration) and emergence of Γ2 weak-FM phase between 31 K and 45.5 K are discussed in consonance with the phonon spectra.

Displacive phase transitions in infinite-layer nickelates from first- and second-principles calculations

“…From an electronic point of view, AFD motions have been widely exploited as practical strategies to optimize properties such as band gap [21][22][23][24][25], metal-insulator transition of RNiO 3 (where R denotes rare-earth) and RMnO 3 [26][27][28][29][30][31][32], and even the superconductivity of cuprates [33][34][35][36]. From the viewpoint of magnetic properties, AFD motions have been revealed to be of direct relevance to magnetic interactions [37][38][39], Néel/Curie temperature [40][41][42][43][44], and magnetic order [45][46][47][48].…”