Evidence of magnetic polaronic states inLa0.70Sr0.30Mn1

Abstract

We have performed x-ray, electrical resistivity, and Raman scattering measurements in La 0.70 Sr 0.30 Mn 1Ϫx Fe x O 3 manganites, with x varying from 0 to 0.40. The appearance of new peaks in the Raman spectra as the Fe content increases is attributed to either otherwise forbidden Raman modes that become active due to symmetry breaking effect or to the phonon density of states features, which arise due to a disorderinduced phenomenon. The softening of some phonon modes suggests the evidence of magnetic polaronic states in the insulating paramagnetic phase of these manganites. Our observations are discussed in connection with the x-ray diffraction and electrical resistivity data.

Fe ion doping effect on electrical and magnetic properties of La0.7Ca0.3Mn1−xFexO3 (0≤x≤1)

“…Souza Filho et al [18] have reported the presence of magnetic polaronic state in Fe doped LSMO system as a consequence of shift in XRD peaks towards lower angles. Very similar behavior are found in XRD pattern for our samples also, we will check out the possible reasons of the increase in lattice volume with Fe doping in connection with electrical and magnetic properties.…”

Study of high‐pressure‐induced phase transition in nanocrystalline perovskite (LaSr)(MnFe)O3by Raman spectroscopy

“…A comparison shows that the peak 1 at ¾465 cm 1 may be due to Fe doping, while the intense peak at ¾518 cm 1 , seen in both the samples but not reported either for the single crystal or in bulk polycrystalline samples, may represent the nano-character of the sample. Souza Filho et al 8 studying rhombohedral La 0.70 Sr 0.30 MnO 3 also observed a broad mode at 524 cm 1 for Fe content ½0.20 and assigned the mode as a density-of-states feature activated by loss of local symmetry in the oxygen sublattice. The enhancement in the intensity of Raman peaks was suggested to be due to the decrease in the average particle size.…”

“…Also, the mode at 524 cm 1 has been assigned to the oxygen sublattice with reduced symmetry. 8 Raman spectra are sensitive to local symmetry reduction since the undistorted cubic perovskite does not exhibit firstorder peaks at all. In oxidized Sr Fe x Ti 1 x O 3 samples, strong indications of a Jahn-Teller distortion around Fe 4C ions is seen through the peaks at 475 and 690 cm 1 , which decrease with increasing iron concentration.…”

“…Such metallic doping studies are few and far between and have not been carried out in detail. 8,9 Substitution in specific sites in the lattice affects the vibrational modes through changes in the mass, bonding strength and bonding configuration, which makes Raman spectroscopy an ideal tool for studying these effects. Moreover, the technique is a useful probe for materials in which lattice as well as electron dynamics strongly interact by means of electron-phonon (el-ph) interactions.…”

“…We report here the pressure dependence of the nanocrystalline La 0. 8 The ambient-pressure X-ray diffractogram, carried out by a Philips 1840 diffractometer using Fe K˛radiation, was indexed for (hkl) values corresponding to the orthorhombic phase. The cluster size distribution was calculated from the broadened X-ray diffraction (XRD) lines by using the Debye-Scherrer equation.…”