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Magnetic characteristics, magnetocaloric effect, and critical behavior of Nd1−xSrxMnO3 compounds by Sr doping (x = 0.2, 0.3, 0.4, 0.5) were studied. All samples maintained orthorhombic structures, but the space group changed from Pnma (No. 62) for x = 0.2, 0.3 to Imma (No. 74) for x = 0.4, 0.5. As Sr doping increased, the Curie temperature (TC), Curie–Weiss temperature (TCW), and magnetization increased, attributed to the double exchange (DE) interaction. A discrepancy between TCW and TC was observed due to the competition between polarons and DE interaction. The critical behavior was investigated systematically using the self-consistent (modified Arrott plots, MAP) method and the Kouvel–Fisher (KF) relation. The KF relation was suitable for the samples with x = 0.2 and 0.5, while the MAP method was suitable for the samples with x = 0.3 and 0.4. Among the Ising, XY, Heisenberg, and mean-field models, the samples with x = 0.2, 0.3, and 0.4 aligned more closely with the mean-field model, except for the x = 0.5 sample. Entropy change (−ΔSM) of Nd1−xSrxMnO3 (0.2 ≤ x ≤ 0.5) increased with the applied field, with the maximum value observed around TC. For the sample with x = 0.3, (−ΔSM) reached 4.315 J/kg K at μ0ΔH = 50 kOe, corresponding to a relative cooling power (RCP) of 280.48 J/kg. Remarkably, the x = 0.4 sample displayed (−ΔSM) of 3.298 J/kg K at μ0ΔH = 50 kOe near room temperature, with the RCP of 283.64 J/kg. These findings underscore the role of Sr doping in tuning the magnetic properties, critical behavior, and magnetocaloric effect of NdMnO3. [ABSTRACT FROM AUTHOR]

The microstructure and magnetotransport of LaMnO3 manganite have been studied. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) at room temperature show that the LaMnO3 sample has a single-phase orthorhombic structure, and the sample particles and elements are densely and evenly distributed. By studying the temperature dependence of resistivity and magnetoresistance (MR), and the magnetic filed dependence of resistivity, it is found that the resistivity versus temperature curves of LaMnO3 show three extreme values in the temperature range of 10–390 K. Firstly, the minimum resistivity at about 70 K comes from the spin polarization tunneling effect. Secondly, there is a maximum resistivity near 189 K due to the inhomogeneity of the polycrystalline sample. Finally, the traditional metal to insulator (MI) transition leads to another maximum resistivity near 241 K, where the corresponding temperature is MI transition temperature (TMI). Moreover, the resistivity of LaMnO3 exhibits a decline as the external magnetic field being increased, implying the presence of MR. In the region of low temperature (close to the TMI), the negative MR reaches 14.68 and 45.28% under 1 T and 4 T applied fields, respectively. The coexistence of two kinds of MR mechanisms in LaMnO3 induced by spin polarization tunneling and Jahn–Teller distortion leads to the enhanced MR within the wide temperature range (10–265 K). [ABSTRACT FROM AUTHOR]

The structure, magnetic, transport and magnetoresistance properties of SrMnO3 sample have been investigated. The SrMnO3 sample has single-phase structure with hexagonal symmetry, which is obtained by the X-ray diffraction. The scanning electron microscope reveals the particles of the sample are evenly distributed. The composition of the SrMnO3 sample is detected using the energy dispersive spectrometer, indicating the element ratio of Sr:Mn:O = 19.25:20.35:60.40. The magnetic, electrical transport and the magnetoresistance effect are studied via the temperature dependences of the magnetization, the resistivity and the magnetoresistance. An antiferromagnetic phase transition near 300 K appears in the SrMnO3 sample, and no significant entropy change can be found in the antiferromagnetic sample. The sample shows the insulator state since the resistance increases gradually with the decrease of temperature. Therefore, SrMnO3 is an antiferromagnetic insulator material. Moreover, the resistivity reduces significantly with the applied magnetic field, indicating an existence of magnetoresistance. Remarkably, the room-temperature magnetoresistance of the antiferromagnetic insulator SrMnO3 reaches 16.68% under 60 kOe field. This work opens our understanding of magneto-transport and magnetic properties of the antiferromagnetic SrMnO3. The discovery of magnetoresistance near room temperature in the antiferromagnetic insulator (SrMnO3) is of great significance for the development of antiferromagnetic spintronics. [ABSTRACT FROM AUTHOR]

The magnetocaloric and ferromagnetic properties of Pr0.7Sr0.3MnO3 film grown on (001) Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT) using pulsed laser deposition technology have been investigated in this work. The X-ray diffraction measurement shows that the (001)-oriented film has been successfully deposited on PMN-PT substrate. The ferromagnetic properties and magnetocaloric effect resulted from ferromagnetic transition are explored via using the magnetic moment versus temperature plots, hysteresis loops, and the magnetic moment versus magnetic field curves. The magnetic moment versus temperature plots (M-T curves) show that with the decrease of temperature, the Pr0.7Sr0.3MnO3 film undergoes a transition from paramagnetic to ferromagnetic phase at temperature close to Curie–Weiss temperature (TCW). TCW (approximately 133 K) is determined by the Curie–Weiss law. The Pr0.7Sr0.3MnO3 film reveals the ferromagnetic feature below TCW, while the film exhibits the paramagnetic state at temperature higher than TCW. Hysteresis loops also confirm that the film reveals ferromagnetic feature at temperature lower than TCW (e.g. ferromagnetic behaviors at 10 and 100 K). The result of hysteresis loops is in accordance with the M-T curves. Besides, entropy change has been investigated in our work. The maximum entropy change of Pr0.7Sr0.3MnO3 film reaches about 2.4 J/kg·K at around TCW under 10 kOe field change, that is close to the entropy change of reference sample Gd (approximately 2.8 J/kg·K within the field change of 10 kOe), suggesting that the Pr0.7Sr0.3MnO3 film on PMN-PT has a great application prospect in magnetic refrigeration. [ABSTRACT FROM AUTHOR]

The magnetic behaviors and magnetocaloric effect (MCE) of Pr0.7Sr0.3MnO3 (PSMO-7) film grown on a (001) SrTiO3 single-crystal substrate by a pulsed laser deposition (PLD) were studied in this paper. X-ray diffraction with a high resolution (HRXRD) measurement shows that PSMO-7 film is grown with a (001) single orientation. The magnetic properties and the MCE related to the ferromagnetic (FM) phase transition of the PSMO-7 film are investigated using the temperature dependence of magnetization M(T) and the magnetic field dependence of magnetization M(H). The M(T) data suggest that with decreasing temperatures, the PSMO-7 film goes through the transition from the paramagnetic (PM) state to the FM state at around the Curie temperature (TC). The TC (about 193 K) can be obtained by the linear fit of the Curie law. Magnetic hysteresis loop measurements show that the PSMO-7 film exhibits the FM feature at temperatures of 10, 100, and 150 K (low magnetic hysteresis can be found), while the film reveals the PM feature with the temperature increased up to 200 and/or 300 K. The research results of M(H) data are consistent with the M(T) data. Furthermore, the magnetic entropy change ( − Δ S M ) of the PSMO-7 film was studied. It was found that the maximum value of ( − Δ S M ) near TC reaches about 4.7 J/kg·K under the applied field change of 20 kOe, which is comparable to that of metal Gd ( − Δ S M of 2.8 J/kg K under 10 kOe), indicating the potential applications of PSMO-7 film in the field of magnetic refrigeration. [ABSTRACT FROM AUTHOR]

The magnetic behaviors and magnetocaloric effect (MCE) of Pr 0.7 Sr 0.3 MnO 3 (PSMO-7) film grown on a (001) SrTiO 3 single-crystal substrate by a pulsed laser deposition (PLD) were studied in this paper. X-ray diffraction with a high resolution (HRXRD) measurement shows that PSMO-7 film is grown with a (001) single orientation. The magnetic properties and the MCE related to the ferromagnetic (FM) phase transition of the PSMO-7 film are investigated using the temperature dependence of magnetization M(T) and the magnetic field dependence of magnetization M(H). The M(T) data suggest that with decreasing temperatures, the PSMO-7 film goes through the transition from the paramagnetic (PM) state to the FM state at around the Curie temperature (T C ). The T C (about 193 K) can be obtained by the linear fit of the Curie law. Magnetic hysteresis loop measurements show that the PSMO-7 film exhibits the FM feature at temperatures of 10, 100, and 150 K (low magnetic hysteresis can be found), while the film reveals the PM feature with the temperature increased up to 200 and/or 300 K. The research results of M(H) data are consistent with the M(T) data. Furthermore, the magnetic entropy change (-ΔSM) of the PSMO-7 film was studied. It was found that the maximum value of (-ΔSM) near T C reaches about 4.7 J/kg·K under the applied field change of 20 kOe, which is comparable to that of metal Gd (-ΔSM of 2.8 J/kg K under 10 kOe), indicating the potential applications of PSMO-7 film in the field of magnetic refrigeration.