Charge-ordering breakdown dynamics and ferromagnetic resonance studies ofB-site Cu diluted Pr1‒xSrxMnO3.

Here, we report the influence of Jahn-Teller active Cu substitution on the charge-ordering (CO) characteristics of one of the well-known manganite Pr0.45Sr0.55MnO3(S55) with a distorted tetragonal structure. Magnetization studies unveil a complex magnetic phase diagram for S55, showing distinct temperature ranges corresponding to various magnetic phases: a ferromagnetic phase dominated by the Double Exchange interaction withTC∼ 220.5 K, an antiferromagnetic phase belowTN∼ 207.6 K induced by CO with a transition temperature ofTCO∼ 210 K consistent with the specific heatCP(T) data, and a mixed phase in the rangeTNTN(T

Effect of Ce substitution on the local magnetic ordering and phonon instabilities in antiferromagnetic DyCrO3perovskites.

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/dCell∼ 6 × 10-3/3.5 ppm (forx∼ 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 (HK∼ 2.58 kOe → 2.07 kOe,K1∼ 36.47 J m-3→ 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 (JS→ 10.08 K to 11.18 K andDAS→ 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 (TSR∼ 3.5 K → 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.

Magnetization reversal, field-induced transitions andH-Tphase diagram of Y1-xCexCrO3.

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 (JAS∼ 0.11 meV andJS∼ 0.85 meV) between the trivalent Ce and Cr enable the positive quartic-anisotropy field (HK4∼ 2.85 × 102Oe) along with the second order anisotropy field (HK2∼ 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 (ΔT∼ 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(∼150 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 (∼ 30 kOe), significant negative exchange-bias field (HEB∼ 2.5 kOe), huge coercive field (HC∼ 22 kOe) and large NM (ΔM∼ 280 emu/mole) are the unique characteristic features of the current investigated system.