[en] La_0.7Sr_0.3Mn_1-xTi_xO₃ films (0 ≤ x ≤ 0.5) were fabricated using chemical solution deposition. It was found that with an increase in Ti content, the lattice constant was first increased due to the substitution of Mn⁴⁺ with Ti⁴⁺, and then it tended to decrease when x ≥ 0.3 due to the substitution of Mn³⁺ by Ti⁴⁺ with a larger ionic radius, as well as when excess oxygen was introduced. With the increase in x, the Curie temperature was decreased and broadened; however, it was found that all the films showed ferromagnetic properties at 300 K, which indicated that the excess oxygen played an important role. The transport properties showed that with an increase in Ti content the resistivity increased and the insulator-metal transition tended to a lower temperature due to the depression of the double exchange and the dilution of the Mn³⁺-O-Mn⁴⁺ network. Moreover, the temperature dependence of magnetoresistance (MR) results showed that with the Ti content increasing, the maximum MR increased and the transition was broadened suggesting that it is useful to tune the MR behaviour through Ti doping, and when x ≤ 0.1 the derived films showed no obvious MR at low temperature; however, when x = 0.3, the film did show obvious MR at low temperature

[en] A systematic study of structural, magnetic, and transport properties was performed on (In_0.85-xFe_0.15Cu_x)₂O₃ (IFCO) and (In_0.80-xSn_0.05Fe_0.15Cu_x)₂O₃ (ISFCO) compounds with x = 0, 0.02, and 0.05. All the studied samples show clear room temperature ferromagnetism and the saturated magnetic moment decreases monotonically with increasing Cu-doping content. Detailed analysis based on the magnetic measurement rules out the ferromagnetism due to Fe₃O₄ and CuFe₂O₄ impurities. A crossover from semiconducting to metallic transport behavior is observed in IFCO samples, whereas only semiconducting behavior is detected in ISFCO. Low temperature resistivity decreases monotonically with increasing Cu-doping level due to the increasing electron concentration. Positive magnetoresistance is observed in IFCO, which also shows an anomalous Hall effect at 5 and 300 K. No magnetoresistance or AHE is found in ISFCO compounds. All the electric transport measurement results can be clarified by a two-channel transport model.

[en] We prepared a series of Bi_1−xLa_xFeO₃ (0 ≤ x ≤ 0.2) ceramics with a sol-gel method and find that both the magnetization and dielectric constant show an abrupt anomaly near a critical field H_c, which is attributed to the destruction of the cycloidal antiferromagnetic spin structure. The critical field H_c decreases substantially from ∼20 T for the x = 0 sample [Y. F. Popov et al., JETP Lett. 57, 69 (1993)] to ∼2.8 T for the x = 0.17 sample and finally to 0 T for the x = 0.2 sample at room temperature (RT). It is also found that H_c increases with decreasing temperature. The variation of H_c with La substitution and temperature can be ascribed to the change in the magnetic anisotropy and isotropic superexchange interaction, respectively. We have also discussed the magnetodielectric effects in these samples in terms of the Ginzburg-Landau theory and the spin-phonon model. Moreover, increasing the doping level of La to 0.15 greatly improves the RT leakage-current and ferroelectric (FE) properties. A RT square-shaped FE hysteresis loop with remnant polarization (2P_r) as high as ∼64 μC/cm² is obtained for the x = 0.15 sample. These results may be important for potential applications in BiFeO₃-based magnetoelectric devices.

[en] We present the results of a systematic investigation of the dc magnetization, ac susceptibility, resistivity and thermopower of Pr_2-xSr_xCoO₄ (x = 1.2, 1.3 and 1.5). The x = 1.2 specimen undergoes a paramagnetic phase above 201.57 K, Griffiths phase between 201.57 and 129.24 K, ferromagnetic cluster-glass phase between 129.24 and 16.19 K and spin-glass state reentrance below 16.19 K. With increasing Sr content, the Griffiths phase and the spin-glass state are suppressed. The specimen shows a p-type semiconducting conduction changing from thermally activated conduction to variable range hopping conduction with increasing Sr doping level. The rich magnetic and transport behaviors are suggested due to the complicated magnetic interactions and Jahn-Teller distortion of the cobalt ions associated with small polarons

[en] a-Axis oriented La_0.8Na_0.2MnO₃ (LNMO) and La_0.8Na_0.2Mn_0.95Cu_0.05O₃ (LNMCO) films with large magnetoresistance (MR) near room temperature are fabricated via chemical solution deposition on yttrium-stabilized zirconia (YSZ) (1 0 0) single crystal substrates. With slight Cu doping, it is found that the growth mode is changed from the layer-by-layer mode of the LNMO film to the island mode of the LNMCO film. The LNMO film exhibits typical transport properties of epitaxial films of manganites. However, the LNMCO film shows transport properties corresponding to polycrystalline films of manganites. The MR value of the LNMCO film at low applied magnetic field is also remarkably enhanced compared with that of the LNMO film below the insulator-metal transition temperature. MR as high as 9% is obtained at a field of 0.05 T at 5 K. The enhanced MR effect for the LNMCO film is attributed to the spin-dependent scattering of polarized electrons at the grain boundaries

[en] Well-oriented LaSr₂Mn₂O₇ thin film with layered perovskite structure was fabricated via the magnetron sputtering method on an a-axis oriented SrTiO₃ single crystal substrate. It exhibits large magnetoresistance and photoinduced decrease in resistance at low temperature. The study of the influence of the current, magnetic field and laser illumination on the charge-ordering (CO) state shows that the CO state at low temperature is sensitive to the external stimulus. The decrease in resistance is attributed to the relaxation of MnO₆ octahedra distortion under the laser illumination as well as the magnetic field

[en] We have measured the temperature dependence of internal friction Q^-1(T), Young's modulus E(T), and resistivity ρ(T) in situ along with the measurements of magnetization M(T) on optimally doped manganites La_0.67Ca_0.33MnO_y with different oxygen contents. With the reduction of the oxygen content y, the Q^-1 peak in the paramagnetic region, suggested to originate from the formation of the magnetic clusters (MC), shifts to a lower temperature and its magnitude decreases and finally disappears. The results of M(T) and ρ(T) indicates that both the effective magnetic moment μ_eff and the hopping distance of electrons decrease with the increase of oxygen vacancies, which may suppress the MC. In addition, the analysis of the results of E(T) indicates that the cooperative effects of lattice distortions may favour the formation of MC

[en] The ferromagnetic (FM) manganite La_0.8Ca_0.2MnO₃ is systematically studied by measurements of internal friction Q^-1, Young's modulus E, resistivity ρ and magnetization M versus temperature T. The resistivity ρ(T) exhibits a metal-insulator transition (MIT) at T_p ∼ 224 K. The magnetization M(T) shows a paramagnetic-ferromagnetic (PM-FM) transition at T_c ∼ 240 K. However, the variation of the internal friction with temperature presents a complicated behaviour. In the FM region, three Q^-1 peaks at temperatures 98, 143 and 163 K are observed in the spectra of Q^-1(T) at the measuring frequency of 1.8 kHz. The origin of three Q^-1 peaks is discussed and attributed to the coexistence of metallic and insulating phases in the FM region. In addition, in the magnetic transitional region, the other two peaks at 182 and 244 K at the measuring frequency of 1.8 kHz are observed. Our results indicate that the internal friction method seems to be a useful technique in studying the coupling between spin, charge and lattice of CMR materials