RESUMEN
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-xCexCrO3solid-solutions have been reported. All the investigated compounds exhibit distorted orthorhombic crystal structure with a distortion factor ofdOct/dCellâ¼ 6 × 10-3/3.5 ppm (forxâ¼ 0.2) forPbnmspace 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 CrO6octahedral tilt angleθrotates 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 forx= 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 (HKâ¼ 2.58 kOe â 2.07 kOe,K1â¼ 36.47 J m-3â 18.97 J m-3) while maintaining the stable Γ4(Gx,Ay,Fz) 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 (JS) and antisymmetric exchange (DAS) constants, which show progressively increasing trend (JSâ 10.08 K to 11.18 K andDASâ 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 (TSRâ¼ 3.5 K â 16.8 K pertaining to the Γ25phase 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.
RESUMEN
We report a systematic study of the magnetic phase diagram in theH-Tplane, negative magnetization (NM), exchange interactions and field-induced spin-flop transitions in the distorted perovskite Y1-xCexCrO3. Locked AFM and weak-FM configurations in Γ4(Gz,Fy,Ax) phase of YCrO3(S= 3/2 ground state) unlocks into the Γ2(Fz,Gy,Cx;FzR,CxR) phase of the canted AFM and FM structures with the dilute substitution of Ce (x⩾ 0.05). The asymmetric and symmetric exchange interaction (JASâ¼ 0.11 meV andJSâ¼ 0.85 meV) between the trivalent Ce and Cr enable the positive quartic-anisotropy field (HK4â¼ 2.85 × 102Oe) along with the second order anisotropy field (HK2â¼ 5.93 × 102Oe). Unlike the pristine YCrO3compound, the Ce incorporated system exhibits a giant fourth-order anisotropy constant (K4= 1.35 × 105erg/c.c.) due to the asymmetric exchange interaction between the trivalent Ce-Cr which further lifts the free energy of the system and causes lag in the onset of AFM ordering showing the significant thermal hysteresis (ΔTâ¼ 10 K) in the field-cooled (FC)-warming measurement protocol as compared to the FC-cooling mode. The H-T phase diagram, mapped from the isothermal magnetization data and differential magnetic susceptibility data with different measurement protocols clearly distinguishes three prominent regions below theTN(â¼150 K), viz (i) long-range canted AFM + weak FM phase (Γ4(Gz,Fy,Ax)), (ii) Γ24mixed phase and (iii) robust Γ2(Fz,Gy,Cx;FzR,CxR) AFM + FM phases. Tunable spin-flopped transition (â¼ 30 kOe), significant negative exchange-bias field (HEBâ¼ 2.5 kOe), huge coercive field (HCâ¼ 22 kOe) and large NM (ΔMâ¼ 280 emu/mole) are the unique characteristic features of the current investigated system.