Structure, magnetic, and transport properties of Ti-substitutedLa0.7Sr0.3MnO3

Abstract

Ti-substituted perovskites, La 0.7 Sr 0.3 Mn 1−x Ti x O 3 , with 0≤ x ≤ 0.20, were investigated by neutron diffraction, magnetization, electric resistivity, and magnetoresistance(MR) measurements. All samples show a rhombohedral structure (space group R3c) from 10 K to room temperature. At room temperature, the cell parameters a, c and the unit cell volume increase with increasing Ti content. However, at 10 K, the cell parameter a has a maximum value for x = 0.10, and decreases for x > 0.10, while the unit cell volume remains nearly constant for x > 0.10. The average (Mn,Ti)-O bond length increases up to x=0.15, and the (Mn,Ti)-O-(Mn,Ti) bond angle decreases with increasing Ti content to its minimum value at x=0.15 at room temperature. Below the Curie temperature T C , the resistance exhibits metallic behavior for the x ≤ 0.05 samples. A metal(semiconductor) to insulator transition is observed for the x ≥ 0.10 samples. A peak in resistivity appears below T C for all samples, and shifts to a lower temperature as x increases. The substitution of Mn by Ti decreases the 2p − 3d hybridization between O and Mn ions, reduces the bandwidth W , and increases the electron-phonon coupling. Therefore, the T C shifts to a lower temperature and the resistivity increases with increasing Ti content. A field-induced shift of the resistivity maximum occurs at x ≤ 0.10. The maximum MR effect is about 70% for La 0.7 Sr 0.3 Mn 0.8 Ti 0.2 O 3 . The separation of T C and the resistivity maximum temperature T ρ,max enhances the MR effect in these compounds due to the weak coupling between the magnetic ordering and the resistivity as compared with La 0.7 Sr 0.3 MnO 3 .

Effects of Selective Dilution on the MagneticProperties of La0.7Sr0.3Mn1-xM'xO3 (M' = Al, Ti)

“…Roomtemperature x-ray diffraction patterns (measured using a SIEMENS-D5000 with Cu-K α radiation) presented in Fig. 1 show that all of the obtained samples are essentially single phase with perovskite rhombohedral (space group R3c) structures, in agreement with previous stud- ies [6,7,8,9,10]. Redox titration experiments (using K 2 Cr 2 O 7 titrant and C 24 H 20 BaN 2 O 6 S 2 as the colorimetric indicator) for checking the oxygen content, 3 ± δ, indicate that the samples are stoichiometric without any significant oxygen excess or deficiency.…”

“…3 below). There have been several explanations for the reduction of T c in other similar cases [6,7,8,9,17]. One explanation is simply that this is due to the suppression of long-range FM order of the localized t 2g spins by local breakdown of the exchange couplings where the substitution occurs [6,17].…”

“…where θ Mn−O−Mn and d Mn−O denote the average Mn-O-Mn bond angle and Mn-O bond length, respectively, to discuss the magnetic and transport properties of manganites [9,19,20,21,22,23]. Kim et al [9] found that Ti substitution in La 0.7 Sr 0.3 Mn 1−x Ti x O 3 increases the Mn-O-Mn bond length and reduces the bond angle.…”

“…Kim et al [9] found that Ti substitution in La 0.7 Sr 0.3 Mn 1−x Ti x O 3 increases the Mn-O-Mn bond length and reduces the bond angle. Based on structural data, the authors calculated the variation of W , finding a decrease of W with x, and related it to the decrease of T c .…”

Magnetic properties of perovskites La0.7Sr0.3Mn0.73+ Mn0.3-xYahyaoui1, Kallel2, Diep3 2016Journal of Magnetism and Magnetic Materials15000View full textAdd to dashboardCite

“…Experiments have been performed to determine magnetic properties of manganese oxides La 1−x A x MnO 3 , with A= Sr, Ca, Ba,.... These materials are currently attracting a considerable attention [3] because of the complex interplay among spins which induces a rich phase diagram as well as the colossal magnetoresistance (CMR) phenomenon [4][5][6]. The rapid development of the CMR field is due mainly to its many applications in particular in spintronics [7][8][9].…”