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We report a detailed study of magnetic properties in manganite (LaPr)CaMnO. In contrast to the usual beliefs, it shows an abnormal upturn deviation from the Curie-Weiss law on the inverse susceptibility curve. Such a non-Griffiths-like phase is further confirmed from the inverse double integrated intensities of electron paramagnetic resonance spectrum. Because La $$^{3+}$$ ions are substituted by Pr $$^{3+}$$ ions with 50% concentrations, the ratio of three ions (La $$^{3+}$$ , Pr $$^{3+}$$ , Ca $$^{2+}$$ ) is close to 1 on A-site sublattice. As a result, some short-range antiferromagnetic (CO AFM) phases come into being in the system due to the existence of localized charge ordering states. Therefore, the upturn deviation from Curie-Weiss law originates from the appearance of short-range CO AFM correlations above $$T_{\text{C}}$$ . Additionally, a magnetic field-driven-metamagnetic transition is found, which gives a main contribution for the large magnetic entropy change (MEC) observed in this sample. Both the Arrott plot and the renormalized MEC curves testify that this transition belongs to first-order magnetic transition. The insignificant hysteresis loop indicate that the inevitable thermal hysteresis can be ignored in the present first-order material implying that it is a potential candidate for the cryogenic temperature magnetic refrigeration. [ABSTRACT FROM AUTHOR]

The critical exponents of second-order phase transition were deduced from magnetic entropy change. Using the magnetic field dependence of entropy change and the Widom scaling relation, some relevant critical exponents can be calculated directly from them. Based on critical exponents, a corresponding Arrott plot can be established as an initial model. Through a limited nonlinear fitting, we can obtain the final critical exponents. This method eliminates the drawbacks of the routine method which relies on the subjective selection of an initial model and involves the multi-step nonlinear fitting process. It was applied to the manganite NdSrCaMnOto verify its utility and feasibility. The spontaneous magnetization obtained using the final critical exponents is consistent with that deduced from the isothermal magnetization measurements, indicating that the utilization of the magnetic field dependence of magnetic entropy change to determine critical exponents is a valid method. [ABSTRACT FROM AUTHOR]

Abstract: An investigation of the structural, transport, magnetic and magnetocaloric properties of polycrystalline La0.5Ca0.4Li0.1MnO3 is presented. A metal–insulatortransition occurs at 162K and shifts to higher temperatures under applied magnetic fields. It shows a large negative magnetoresisance (MR) effect (40% at 3T field) in a wide temperature range of 200K. Magnetic measurements and Arrott plot analysis reveal that the system undergoes a second order paramagnetic–ferromagnetic (PM–FM) phase transition at T C =250K. A large magnetocaloric effect (MCE) occurs in vicinity of the phase transition. The magnetic entropy change attains 4.16J/(kgK) under field change ∆H=3T and 2.11J/(kgK) under ∆H=1T. It possesses a large relative cooling power (RCP= 140J/kg) and a relatively wide temperature span ( =34K) for ∆H=3T. By using the equation , we examine the relationship between the magnetic entropy change and the resistivity in the system and find a poor satisfiability of the relationship between them. This can be understood by the significant magnetoresistance originating from the electron tunneling between the FM domains. [Copyright &y& Elsevier]

In this paper, we present the investigations of electron paramagnetic resonance on perovskite manganite PrSrMnO and Ga-doped PrSrMnGaO. The temperature dependent paramagnetic resonance spectra parameters (effective g-factor, peak-to-peak linewidth Δ H and double integrated intensities) have been used to study the paramagnetic spin correlations and spin dynamics. The gradual increase of effective g-factor is attributed to the presence of orbital ordering above T. The model fittings of temperature dependent double integrated intensities reveal Arrhenius law is appropriate for describing PrSrMnGaO instead of PrSrMnO system. As for PrSrMnO, the broadening of linewidth with the temperature increase origins from the contribution of small polaron hopping in the PM regime. However, as for PrSrMnGaO, the broadening of EPR linewidth can be understood with the spin-lattice relaxation mechanism. [ABSTRACT FROM AUTHOR]

Structural and magnetic properties of Bi0.5 Ca0.5-xBaxMnO3 (x = 0, 0.03, 0.05, 0.07 and 0.10) samples with charge ordering (CO) state and C-type antiferromagnetic (AFM) magnetic structure have been studied systematically. With increasing Ba-doping level, both CO and AFM are weakened. From the micro-magnetic analysis, we clarify the ambiguity about the Néel temperature TN in bismuth-based perovskite manganites. We find that the paramagnetic (PM)-CO/AFM transition temperature TCO at high temperature is the onset temperature of the PM-AFM transition, while customarily so-called TN at low temperature indicates the finish of the PM-AFM transition. Both the macro- and micro-magnetic data show that, in all the samples, only AFM state coexists with PM matrix below CO transition and above TN, while AFM state coexists with ferromagnetic (FM) state and PM state at lower temperature below TN. [ABSTRACT FROM AUTHOR]

We have studied the magnetotransport properties of the La[sub l.4]Sr[sub l.6-y]Ba[sub y]Mn[sub 2]O[sub 7] (y≤0.50) samples with a bilayered perovskite structure. For lightly doped samples, the metal-insulator transition accompanying a three-dimensional ferromagnetic transition can be understood commonly in terms of the double-exchange interaction. For heavier doped samples, the metal-insulator transition remains without a ferromagnetic transition and shifts to higher temperature with increasing Ba doping level. On account of the coexistence of short-range ferromagnetic ordering and paramagnetic state, the results can be explained by a recent percolation model based on phase separation. The percolative metal-insulator transition is consistent with the relative ferromagnetic metallic fraction change with temperature and doping level. [ABSTRACT FROM AUTHOR]

Abstract: The substitution of Ga for Mn in manganite Nd0.6Dy0.1Sr0.3MnO3 with a ferromagnetic (FM) ground state has been performed to study the influence of the Mn-sublattice magnetic ordering on the magnetic rare-earth sublattice. It is found that the substitution of Mn3+ with Ga3+ ions results in a sharp decrease of T C , reflecting the reduction of the double-exchange interactions strength J Mn–Mn . At the same time, a depinning effect of the rare-earth magnetic moment has been observed. This behavior unambiguously proves that the exchange interaction between Mn and rare-earth ions J Mn–R strongly influences the rare-earth magnetic ordering at temperatures below T C and stabilizes the rare-earth magnetic ground state. [Copyright &y& Elsevier]

For achieving more functionalities of perovskite manganese oxides film, an epitaxial La 0.8 Sr 0.2 MnO 3 (LSMO) film was deposited on a flexible substrate (mica) by pulsed laser deposition. The film shows a paramagnetic-ferromagnetic (PM-FM) phase transition at 134 K together with metal-insulator transition (MIT) at 149 K. The measurement of hysteresis loop indicates that the easy-magnetization axis lied in film plane. The transport behavior can be fitted well with the small polaron model, giving out the activation energy E hop = 176.9 meV. Different from the common anisotropic magnetoresistance (AMR) in manganite film, an isotropic magnetoresistance (IMR) effect was observed in LSMO film and the relatively small thickness of LSMO film (∼ 50 nm) is a major reason for it. After the cyclic flexural bending for 1.0 × 104 times, we found the magnetic properties of LSMO film were improved. Micromagnetic detection shows that the activation energy for polaron hopping (E a = 144.7 meV) remarkably decreases by the cyclic flexural bending process. We suggested that the inhomogeneous/incompact part located at the zone of neighbouring domains become uniform and tight after circulating bending, which facilitates the rotation of domains and the polarons hopping so that the magnetic and electronic performance are enhanced. • A flexible pervoskite manganite film has been fabricated by PLD. • The film shows an exchanged polaron interactions in transport behavior. • An isotropic magnetoresistance effect was observed in film. • The magnetization and electronic transport property have been promoted after the cycling bending. [ABSTRACT FROM AUTHOR]

• The electronic phase separation has been observed in La 0.8 Sr 0.2 MnO 3. • The state of magnetic skyrmion exists in the temperature region of 290 K–306 K. • A large DM interaction exists in the interface of LaMnO 3 /SrMnO 3. Magnetic skyrmions, being one of the most promising candidates for the next generation memory-type application due to their nanometer-size and efficient current-driven dynamics, are mainly found and studied in alloy helimagnets in which the spin-orbit coupling induced by Dzyaloshinskii-Moriya interaction (DMI) enables noncollinear spin alignment and skyrmion formation. In this paper, we report a possible finding of skyrmions crystal near room-temperature in centrosymmetric structures perovskite manganite La 0.8 Sr 0.2 MnO 3 (LSMO). Based on the measurements of isothermal magnetization around the Curie temperature (∼298 K), an unusual magnetic behavior of a discontinuous magnetization was observed and existed only at moderate magnetic field region together with a narrow temperature range from 306 to 290 K. Apart from this range, all curves return to conventional magnetic behavior of continuous change with external magnetic field. This characteristic has been frequently observed in some reported helimagnets (such as FeGe, MnSi), implying the possible existence of skyrmions crystal in LSMO. To further unveil the physical origin and underlying mechanisms, we performed the first-principles calculation for LSMO compound and a large DMI (Δ E DMI = 13.46 meV, d 1 = 1.68 meV) was found to exists at the interface of LaMnO 3 / SrMnO 3 layers. This result not only supports our experimental findings in the present composition but also is consistent with the formation mechanism of magnetic skyrmions. [ABSTRACT FROM AUTHOR]

Abstract Electronic phase separation (EPS) plays a key role in elucidating the effects of complexity on emergent behavior for correlated electronic materials. In this work, we thoroughly studied a robust EPS existed in perovskite manganite La 0.825 Sr 0.175 MnO 3. Results show that a typical paramagnetic-ferromagnetic (PM-FM) phase transition and a metallic-insulating phase transition occur at 285.4 and 295 K, respectively. Electron paramagnetic resonance (EPR) spectroscopy confirms that there are a double peaks rather than a single peak structures in the temperature region of 290 K ≤ T ≤ 315 K, indicating that an obvious EPS state generates in this compound. Based on the variation of EPR intensities, we found that the FM composition continues to increase with the decrease of temperature in the whole EPS region. Moreover, it causes a percolative-like metallic-insulting transition when the percolative threshold approach ∼22.63 % which is nearly equivalent to 25.34 % obtained by calculating the ratio of spontaneous magnetization against theoretical saturated magnetization. Detailed phase diagram shows that the EPS state not only occupies most of PM region but also a state of multiphase coexistence is also found. [ABSTRACT FROM AUTHOR]

Electron paramagnetic resonance (EPR) was applied extensively to probe the phase separation and spin relaxation mechanism in the perovskite manganites. In this study, we conducted the measurement of EPR for the perovskite manganites (La 0.5 Pr 0.5 ) 0.67 Ca 0.33 MnO 3 . We found that both paramagnetic and ferromagnetic resonance peaks simultaneously emerged on resonance spectrum near below T C , exhibiting a typical characteristic of phase separation. The linewidth of EPR spectrum progressively enlarged upon the rising of temperature in the temperature range of T > T C and a quasilinear variation of peak-peak width was observed at T C < T < 500 K. In contrast to the usual beliefs that the variation of peak-peak linewidth can be understood either by spin-lattice relaxation or by spin-spin relaxation, however, the linewidth behavior observed here shows a coexistence of two spin relaxation mechanisms. We proposed that the inhomogeneous electronic phases due to the intrinsic self-organizing growth were responsible for the appearance of multiple spin exchange interactions and variational relaxation mechanism. This finding would be possible to pave a new way for further investigating magnetic correlations and spin dynamics in the paramagnetic hole-doped manganites. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we have studied the magnetic and magnetocaloric properties of the perovskite manganite Pr0.55Sr0.45MnO3. It shows a sharp paramagnetic–ferromagnetic phase transition at 291K and possesses a moderate magnetic entropy change near room temperature. In addition, a large relative cooling power (143.64J/kg) and a wide temperature range (84K) have been found in this material. Compare with the Landau model, we find that the itinerant electrons mainly contribute the larger magnetic entropy change at paramagnetic region. [Copyright &y& Elsevier]

Abstract: The magnetic behavior and electronic transport in the half-doped manganite Nd0.5Ca0.25Sr0.25MnO3 have been investigated. The critical exponents are studied by using isothermal magnetization methods. The results show that the paramagnetic–ferromagnetic transition is second order and the magnetic interaction is satisfied with the prediction of three-dimensional Heisenberg model. The electronic transport belongs to the percolation mechanism. These findings demonstrate that the critical behavior of the magnetic transition and conductivity for manganites are related to Mn-site ordering degree. [ABSTRACT FROM AUTHOR]