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The evolution of the Griffiths phase (GP) with a ferromagnetic metal (FMM) cluster above the Curie temperature (TC) and its effect on the magnetic properties, electrical transport, magnetoresistance (MR), and magnetocaloric effect (MCE) is studied comprehensively, using bulk compounds of La1−xBaxMnO3 (0.15 ≤ x ≤ 0.25) with different lattice distortions but with the same structural symmetry and space group. These La1−xBaxMnO3 samples show ferromagnetic transition at TC increasing from 229 K for x = 0.15–300 K for x = 0.25, in addition to the presence of GP with FMM clusters in the paramagnetic (PM) region, which have been confirmed by the combination of magnetization (susceptibility) measurements, the GP theory, and electron paramagnetic resonance technology. With increasing the Ba2+ ion doping, GP temperature (TG) and TC of La1−xBaxMnO3 are increased, and the GP regime is strengthened. The GP ratio in the PM region reached 27.7% for the sample with x = 0.20. The resistivity decreases and the FMM phase increases with increasing x from 0.15 to 0.25, which can be explained by the decrease in the bandgap (Eg) and the enhancement of the double-exchange effect. Remarkably, large room-temperature MR (∼44.7%) can be observed in the sample with x = 0.25 under 60 kOe, which is related to the presence of the GP regime. Furthermore, the MCE is also affected by the GP regime, and it is deduced that the magnetic transition is of second order. The value of magnetic entropy change (| Δ S M |) reaches 3.04 J/kg K near room temperature for the sample with x = 0.25 under 50 kOe. This value is associated with a relative cooling power (RCP) of 248.1 J/kg. For the sample with x = 0.15, the value of RCP reaches 307.6 J/kg under 50 kOe. The discovery of the MR and MCE near room temperature is of great significance from the practical application of perovskite manganites in magnetic sensors and magnetic refrigerants. [ABSTRACT FROM AUTHOR]

The transport properties and magnetoresistance (MR) effect of Pr0.7Sr0.3MnO3 (PSMO) film on SrTiO3 (STO) substrate are investigated in this work. The PSMO film is grown on (001) STO substrate by pulsed laser deposition (PLD). The high-resolution X-ray diffraction (XRD) pattern suggests that the Pr0.7Sr0.3MnO3 film shows the out-of-plane single orientation. Atomic force microscopy (AFM) image shows that the surface of the film is smooth. In addition, the significant interference peaks can be found in the XRD. All these confirm the high quality of the PSMO film grown on STO substrate to some extent. The magnetotransport properties and the MR associated to the double exchange (DE) interactions of the Pr0.7Sr0.3MnO3 film have been studied by the resistivity versus temperature and resistivity versus magnetic field data. The temperature dependence of resistivity shows that the film sample undergoes a metal-to-insulator (MI) transition at MI temperature TMI. The TMI gradually increases with the increase of applied magnetic field. Under different fields of 1 T, 2 T, 4 T and 6 T, the maximum values of negative MR (MR = [ρ-ρ0/ρ0] × 100%) reveal about 47.16%, 53.16%, 86.59% and 92.22%, respectively. Compared with other reports on bulk polycrystalline PSMO compounds and polycrystalline PSMO films, the PSMO film on STO in our work has relatively large MR, which is related to the single-oriented growth of PSMO/STO film. The large MR is conducive to the practical applications in magneto-electronic devices. The applied magnetic field dependence of resistivity shows that near TMI, the resistance changes significantly with the change of the applied field. This also implies that there is a large MR at around TMI, which can be explained by the traditional DE mechanism. [ABSTRACT FROM AUTHOR]

PrSrMnO (PSMO) films were fabricated on (0001) sapphire substrates by pulsed laser deposition. The structure and transport properties of the films have been investigated. Several textures and disorder coexist in the PSMO films and result in the colossal magnetoresistance (MR) effect at a wide temperature range of 5-210 K. Colossal MR at the wide temperature region provides opportunities for practical application in manganite film devices. Our research results demonstrate that the textures and the disorder state induced by multiple growth orientations can strongly influence the transport properties of film. [ABSTRACT FROM AUTHOR]

We have grown PrSrMnO/LaCaMnO bilayer on (001) single crystal SrTiO substrate by pulsed laser deposition technique. The bilayer film is well (001) orientation grown with high crystalline quality. When the applied magnetic field increases up to 9 T, only metal-like transport behavior can be observed below room temperature. The Low-field MR (LFMR) as large as ~−73% has been achieved at an applied field of 1 T and the magnetoresistance (MR) can reach a value of ~−641% at an applied field of 9 T. Ferromagnetic (FM) clusters percolation accompanied with the collapse (melting) of charge-ordered (CO) state in LaCaMnO may be responsible for the enhancement of MR. Moreover, the disappearance of exchange bias (EB) in the bilayer demonstrates the existence of FM clusters percolation at the PSMO/LCMO interface. Large LFMR provides possibilities in developing manganite-based FM/CO film devices. [ABSTRACT FROM AUTHOR]

The perovskite hexagonal SrMnO 3 manganite with four layers (4H-SrMnO 3) have been one of the hot topics in materials science due to the physical characteristics of antiferromagnetic, ferroelectric, and thermoelectric effects. The transport properties and magnetoresistance (MR) effect of 4H-SrMnO 3 have seldom been reported. The structure, temperature coefficient of resistivity (TCR), magnetic and magnetotransport properties of the 4H-SrMnO 3 SrMnO 3 manganite obtained by solid state reaction have been investigated in this work. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) measurements at room temperature reveal that the SrMnO 3 sample exhibits a pure hexagonal symmetric structure, with uniform distribution of particles and elements. Under applied magnetic fields of 2000 Oe, the SrMnO 3 sample exhibits a transition from antiferromagnetic (AFM) to paramagnetic (PM) behavior at approximately 280 K, known as the Néel temperature (T N). The resistance is influenced by the magnetic field, but overall exhibits an insulating state. Remarkably, the SrMnO 3 sample shows significant MR effect near room temperature. The negative MR near room temperature varies from 5.8 % with 1 T field to 16.8 % with 6 T field, indicating an existence of obvious MR in the hexagonal AFM SrMnO 3 manganite. Furthermore, the maxmium value of TCR reaches 4.34 % K−1 near room temperature. These findings of room-temperature TCR and room-temperature MR in the AFM 4H-SrMnO 3 hold immense value for the research and potential application of the AFM spintronics and devices. • The perovskite hexagonal 4H-SrMnO3 with AFM state have been obtained. • The sample exhibits an AFM to PM transition at approximately 280 K. • The resistance is influenced by the field, leading to the obvious MR in 4H-SrMnO3. • Near room temperature, the maxmium TCR value for 4H-SrMnO3 reaches 4.34 % K−1. [ABSTRACT FROM AUTHOR]

The metamagnetic transition, magnetocaloric and magnetoresistance effects are investigated in polycrystalline Sm 0.55 (Sr 0.5 Ca 0.5 ) 0.45 MnO 3 (SSCMO) manganite. A sharp magnetization jump at Curie temperature ( T C ) 73.5 K with large thermal hysteresis is observed. Magnetic measurements and Arrott plots analysis indicate that the transition is first order in nature. Under a low magnetic field change of 1 T, the magnetic entropy change exhibits a peak value of − Δ S M max ( T ) =4.01 J/kg K with relative cooling power (RCP) value of 44.1 J/kg in the vicinity of T C . The mechanism of charge conduction in insulator phase is polaron transport. Large negative magnetoresistance ratio with value of ~99% is obtained within a broad temperature range below metal insulator transition temperature under 1 T magnetic field. These results indicate the potential applications of SSCMO in magnetic refrigeration and spintronics devices. [ABSTRACT FROM AUTHOR]