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The polycrystalline Sr2IrO4 has been studied using Raman spectroscopy and magnetization. The magnetizationmeasurement confirms canted antiferromagnetic transition below TN= 240 K. Temperature dependent Raman spectroscopic study on Sr2IrO4 has been carried out down to 90 K to investigate the correlation among vibrational and spin degree of freedom. We specifically investigated Ir-O-Ir vibrations (R2 mode) which is related to octahedral tilt as well as exchange interaction. Anomalous hardening of R2 mode below Neel temperature is observed and the deviation of the phonon frequency from the anharmonic behavior is shown to scale with the square of the reduced magnetization. [ABSTRACT FROM AUTHOR]

The magneto-electric compound Cr2O3 has been subjected to temperature dependent Raman spectroscopy, carried out from 80 K to 400 K. The sample is reported to be an antiferromagnet below 307 K i.e. the Neel temperature (TN). The behavior of Raman modes is investigated at low temperatures, where the coefficient of magneto-electric coupling is previously reported to show anomalous behavior. This study elucidates the significance of spin-lattice coupling in the mechanism of magneto-electric coupling. The study provided direct evidence of involvement of lattice and variation in local symmetry in the temperature window where the Cr2O3 shows magneto-electric effect. [ABSTRACT FROM AUTHOR]

We report on the structural and spectroscopic studies on HoCr1-xFexO3 (x = 0 and 0.5) compounds. X-ray diffraction studies confirmed the phase purity of the compounds. An increase in the lattice parameter as well as bond lengh are evident with the addition of Fe at Cr-site in HoCrO3 compound. The addition of Fe content to Cr-site in HoCrO3 compound led to shift the position of phonon mode in Raman spectra as well as position of vibrational bands in FTIR specta recorded at room temperature. Temperature dependent Raman studies on both the compounds indicate the absence of structural phase transition in the investigated temperature region. [ABSTRACT FROM AUTHOR]

Temperature dependent Raman spectroscopy study of CuO from room temperature down to 150 K is presented. New phonon modes appear below the commensurate antiferromagnetic ordering temperature (TN =213 K). The optical phonon Agmode occurring at 301 cm-1 showed strong modulation while Bg mode occurring at 350 cm-1 showed weak modulation in frequency across TN establishing strong spin-phonon coupling in this compound. In contrast, the Bg mode occurring at 630 cm-1 showed no clear signature of modulation due to magnetic order. The behaviour is explained by considering the lattice dynamical picture of the vibrational modes. [ABSTRACT FROM AUTHOR]

Low temperature Raman spectroscopy has been carried out on polycrystalline Eu0.75Y0.25MnO3 compound synthesized by solid state reaction route. X-ray diffraction study confirms orthorhombically distorted perovskite (space group Pbnm) structure and Raman spectra confirm that all phonon modes are consistent with group theoretical predictions. Anomalous evolution of phonon modes line width with temperature indicates towards presence of antiferromagnetic fluctuations well above the Neel temperature. [ABSTRACT FROM AUTHOR]

Low temperature Raman spectroscopy has been carried out on polycrystalline Eu0.75Y0.25MnO3 compound synthesized by solid state reaction route. X-ray diffraction study confirms orthorhombically distorted perovskite (space group Pbnm) structure and Raman spectra confirm that all phonon modes are consistent with group theoretical predictions. Anomalous evolution of phonon modes line width with temperature indicates towards presence of antiferromagnetic fluctuations well above the Neel temperature. [ABSTRACT FROM AUTHOR]

The magneto-electric compound Cr2O3 has been subjected to temperature dependent Raman spectroscopy, carried out from 80 K to 400 K. The sample is reported to be an antiferromagnet below 307 K i.e. the Neel temperature (TN). The behavior of Raman modes is investigated at low temperatures, where the coefficient of magneto-electric coupling is previously reported to show anomalous behavior. This study elucidates the significance of spin-lattice coupling in the mechanism of magneto-electric coupling. The study provided direct evidence of involvement of lattice and variation in local symmetry in the temperature window where the Cr2O3 shows magneto-electric effect. [ABSTRACT FROM AUTHOR]