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Due to the coexistence of spin-orbital coupling (SOC) and electron correlation interactions, double perovskite iridates are considered ideal material to investigate the Mott insulating states and Kitaev interactions. In this work, we studied the spin-orbital coupling (SOC), spin-phonon coupling (SPC), and Kitaev magnetism in antiferromagnetic La 2 ZnIrO 6 single crystal by magnetometer and Raman scattering spectroscopy measurements. Based on the temperature dependence of the magnetization under different magnetic fields, we found that all the initial temperatures of the paramagnetic-ferromagnetic transition were basically concentrated around 8.8 K, while the temperature of ferromagnetic-antiferromagnetic transition continued to decrease from 7 K to 2 K. Anomalous modes of frequency softening at magnetic-order temperature were detected from the polarized Raman scattering spectra, indicating the presence of strong spin-phonon coupling and Kitaev interaction in La 2 ZnIrO 6. [ABSTRACT FROM AUTHOR]

In an effort to explore new electronic devices with multiple functionalities, there are numerous studies of depositing perovskite oxides on flexible substrates to replace rigid silicon‐based wafer in device applications. In this study, the growth of pseudocubic SrRuO3 single‐crystal thin film on a transparent and flexible muscovite is established. The experimental results confirm that the Curie temperature TC and the magnetic properties can be effectively tuned via the mechanical strain due to the facilitation of flexible substrate. It is found that the tensile strain increases while the compressive strain decreases the spontaneous magnetization for the thin film suffering the same ±0.24% strain. Based on the study of critical behavior, the critical exponents β = 0.543(19) and γ = 1.262(1) with the critical temperature TC = 159.04(5) K and TC = 159.10 K, respectively, are obtained by the modified Arrott plot. The set of critical exponents matches well with Widom scaling relation and the scaling equation, indicating these critical exponents are intrinsic for SrRuO3 thin films. Moreover, it is achieved that the SrRuO3 thin films exhibit a long‐range interaction coupled with 3D‐Heisenberg type. [ABSTRACT FROM AUTHOR]

Exploiting two-dimensional van der Waals (2D vdW) room temperature ferromagnetic materials is always significant and valuable work. However, the actual number of satisfactory materials with intrinsic ferromagnetism is very limited. Here, the 2D layered Cr4Te5 epitaxial films prepared by a pulsed laser deposition technique were confirmed to hold a ferromagnetic ordering state up to 300 K. We find that the Cr4Te5 films can easily achieve epitaxial growth along a single orientation of the hexagonal Al2O3(0001) substrate. However, as for the cubic SrTiO3(001) and multiphase structure mica substrates, the Cr4Te5 films only show uniaxial growth instead of epitaxial growth. Based on the investigation of electronic transport in the metallic regime, it is revealed that the interaction of electron–magnon scattering only exists in the lower temperature region. Our work renders 2D vdW Cr4Te5 crystals a very promising material for developing practical spintronic nanodevices. [ABSTRACT FROM AUTHOR]

Apart from the impact of different substrates on epitaxial thin films due to lattice constant mismatches, the properties of epitaxial thin films are also influenced by the same substrates with different crystal orientations. Herein, the (111)‐oriented SrTiO3 (STO) substrates are used to fabricate the LaCoO3 (LCO) epitaxial thin films rather than the more common (001)‐oriented STO substrates. It undergoes one paramagnetic–ferromagnetic phase transition around 50 K. This phase transition is similar to the previously observed for (001)‐LCO/STO, but the Curie temperature (Tc) is significantly lower than the previously reported 80 K. To investigate the decrease of Tc and gain further insight into the phase transition, the critical behavior analysis of thin film is performed. The critical exponents are determined to be β = 1.591(3) and γ = 0.937(1) by reconstructing a modified Arrott plot, and the reliability of these exponents is confirmed by the Widom scaling relation. Using the renormalization group theory approach, it is discovered that the film has a long‐range magnetic interaction with space dimensionality d = 2 and spin dimensionality n = 1, and the magnetic exchange interaction decays J(r)≈r−2.4473. [ABSTRACT FROM AUTHOR]

We have presented the structural, surface morphology, magnetic and resistivity data for perovskite LaMnO3 epitaxial thin films which are fabricated on well-oriented (001) LaAlO3 substrates by pulsed laser deposition technique. X-ray diffraction 𝜃 – 2 𝜃 linear scans and reciprocal space mapping measurement confirm that the out-of-plane and in-plane epitaxial relationship are LMO(001)/LAO(001) and LMO(110)/LAO(110), respectively. Surface roughness determined by atomic force microscopy was no more than 0.3 nm. In the whole studied temperature range, all films only show a paramagnetic behavior instead of any magnetic phase transitions. Correspondingly, the electron transport behaviors always exhibit an insulting state as the temperature changes from high to low. However, we find that none of theoretical models can individually be used to understand their conductive mechanisms. Further studies indicated that charge carries of high and low temperature region obey adiabatic and nonadiabatic small polaronic hopping mechanisms, respectively. This finding offers new ways of exploiting the abnormal ferromagnetism in LaMnO3 multilayer thin films. [ABSTRACT FROM AUTHOR]

The critical behavior of single phase Y2Fe17 melt-spun ribbons with the Th2Fe17-type crystal structure has been studied around the transition temperature (TC). This alloy undergoes a second-order ferromagnetic (FM)–paramagnetic (PM) phase transition at TC = 301 K. Various techniques, such as the modified Arrott plot, Kouvel–Fisher method, and critical isotherm analysis, were used to determine the critical exponents that were found to be β = 0.226(3), γ = 1.296(2), and δ = 6.804(5). The universality class of the critical phenomenon in the Y2Fe17 ribbons can be explained with the help of the renormalization group theory approach, in which the magnetic properties show a feature changing from three (3D)- to two-dimensional (2D) Ising model. The first-principles calculations based on density functional theory qualitatively explain the experimental results, confirming the strong correlation between lattice atoms and critical behavior in magnetic intermetallic Y2Fe17. [ABSTRACT FROM AUTHOR]

Crystal phases growth with corresponding preferential orientations plays a key role in determining functional characteristics of thin films. Here, a detailed comparison study on optical transmission and carrier transport of Ba 0.96 La 0.04 SnO 3 (BLSO) films which was fabricated on (001) and (111)-oriented SrTiO 3 substrate were reported. Two kinds of films all show a high optical transmittance (~ 82.5%) in the visible region. However, the optical transmittance of (001)-oriented film depends strongly on film thickness while the (111)-oriented film shows independence of film thickness. Although their electronic transports display a typical metallic behavior, the actual resistivity of (111)-film is two times larger than that of (001)-film. Based on the density functional calculation, we find that the charge distributions of Sn and O are much more denser on (001)-plane than (111)-plane, indicating that (001)-plane not only has a larger carrier concentration but also the electrons transport more easily on it. A phenomenological model was also applied to quantify the resistivity ration ρ 111 /ρ 001 = 1.7, basically comparable to the experimental value of 2.5. Our results will offer experimental basis and theoretical reference for the design and application of perovskite BLSO transparent conducting films. • Pervoskite BaLaSnO3 thin films with different orientations have been fabricated by PLD. • The (001)-film shows optical transmittance dependence on film thickness but (111)-film without this feature. • The (001)-resistivity is smaller than that of (111)-resistivity. • The larger charge density on (001) plane is main reasons for the observed difference. [ABSTRACT FROM AUTHOR]

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 magnetic and electronic transport properties of the lightly doped SrRu1-x Fex O3 (x ≤ 0.15) have been studied. All the samples show a paramagnetic-ferromagnetic phase transition and hysteresis effect. With the increase of Fe, the temperature of magnetic phase transition decreases but coercive field increases indicting the existence of antiferromagnetic interaction and magnetic-crystalline anisotropy. In low temperature, all the doping samples exhibit an insulating behavior while metal feature appears only at x ≤ 0.10 samples. The induced disorder suppresses the itinerant property of Ru 4d electron due to Fe random occupation. As a result, the ferromagnetism is weakened and metal-insulator transition is suppressed. [ABSTRACT FROM AUTHOR]

We report a detailed study of magnetic and transport properties in perovskite manganites Nd0.55Sr0.45Mn1-xGaxO3 (0.00≤x≤0.20). The Ga substitution induces the B-site disorder together with a distinct suppression of the metal-insulator transition and ferromagnetic-paramagnetic transition. Due to an appearance of inhomogeneous magnetic clusters, the Griffiths-like phase is observed in 0.08≤x≤0.10 compounds. Meanwhile, with the increase of Ga concentration, the carriers self-trap into magnetic polarons. Because the oxygen sublattice distortion causes the variation of the phonon density of state, an additional Raman vibrative mode appears in the system. [ABSTRACT FROM AUTHOR]

The electronic transport and magnetism in half-doped Nd0.50Ca0.25Sr0.25MnO3 manganites have been investigated. Contrary to general half-doped system, it only displays a paramagnetic-ferromagnetic phase transition associated with an insulator-metal transition instead of with any features of charge ordering. With the decrease of temperature, an electronic phase separation and spin glass state occur in low temperature. We suggest that the A-site cation disorder induced by the size mismatch between Sr2+ ion and Ca2+ ion is mainly responsible for this phenomenon. [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]

The structural, Hall effect, electronic transport, and magnetic properties of Ge0.96−xBixFe0.04Te epitaxial thin film as prepared by pulsed laser deposition technique were reported. X-ray diffraction patterns including linear scans and phi scans confirmed that all films are high quality epitaxy and crystallinity. With the substitution of high valence Bi for Ge element, we found that the previous carriers of hole were changed to electron, which was testified by the negative slopes obtained from the measurements of Hall effect under different temperatures. The electronic transports show a typical semiconductor behavior and can be understood by the small polaron hopping model because the lattice distortions increase the electron-phonon interaction. An obvious ferromagnetic properties occur in the high Bi-doping Ge0.64Bi0.32Fe0.04Te rather than in that with low Bi-doping concentration, indicating that the ferromagnetic establishment is entirely dependent on carrier's transmissions. The first-principles calculation performed on this system also reveals that the ferromagnetic state exactly exists in the present n-type diluted magnetic semiconductors with Bi co-dopants. [ABSTRACT FROM AUTHOR]

Background: In recent years, since the molecular docking technique can greatly improve the efficiency and reduce the research cost, it has become a key tool in computer-assisted drug design to predict the binding affinity and analyze the interactive mode. Results: This study introduces the key principles, procedures and the widely-used applications for molecular docking. Also, it compares the commonly used docking applications and recommends which research areas are suitable for them. Lastly, it briefly reviews the latest progress in molecular docking such as the integrated method and deep learning. Conclusion: Limited to the incomplete molecular structure and the shortcomings of the scoring function, current docking applications are not accurate enough to predict the binding affinity. However, we could improve the current molecular docking technique by integrating the big biological data into scoring function. [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]

In this paper, we study the absorption efficiency spectra and electric field distribution of Ag nanoparticles enveloped with Fe 3 O 4 nanoshell by applying the discrete dipole approximation theory. Three kinds of Ag@Fe 3 O 4 core–shell nanoparticles (NPs) structural variables, including the same core with different shell thickness, the same outer shell with different core radius, and the same size of total radius have been discussed in detail. The simulated results show that the localized surface plasmon resonance (LSPR) peak wavelength of NPs is linearly proportional with the volume fraction of the shell, regardless of the outer shell material property and one structural variable. Compared to the plasmon resonance peak of the Ag nanoparticles, the LSPR shift of the NPs is dependent on both the total particles size and the outer Fe 3 O 4 shell thickness. The electric field around the surface of NPs becomes weaker under the same damping when the core radius decreases. Based on the plasmonic characteristics revealed in this study, it is suggested that it would provide some key guidances for designing the future NPs structural variables for a broad range of plasmon applications. [ABSTRACT FROM AUTHOR]

Wide bandgap semiconducting perovskite La:BaSnO 3 is a promising candidate for next-generation transparent conducting oxides due to its high electron mobility and excellent oxygen stability. In this work, in order to realize flexible optoelectronics, an epitaxial growth of Ba 0.96 La 0.04 SnO 3 (BLSO) film on a flexible mica via van der Waals epitaxy is established. The high quality heteroepitaxy and crystallinity of BLSO films are confirmed by a combination of X-ray diffraction and atomic force microscopy. Results show that the flexible BLSO films not only retain a high transmittance of more than 85 % in the visible region under unbending conditions, but also exhibit a remarkable transmittance of 90 % under bending conditions. Due to the fixed lattice mismatch and misfit strain, an anomalous electronic transport behavior, showing as a continuous enhancement of resistivity dependence on the decreasing temperatures from high to low, was observed for all BLSO films. Although the resistivity of flexible BLSO films is a slight larger than that of growth on rigid counterparts, the resistivity of 7–10 m Ω  cm is also satisfied with actual application for optoelectronic devices at room-temperature. Our study marks that the technological advancements toward realizing flexible optoelectronics are promising by utilizing perovskite oxides La-doped BaSnO 3 and mica substrate. [ABSTRACT FROM AUTHOR]

• We confirmed that the FM-PM phase transition observed for cubic ErNi 2 Laves compound belongs to second-order magnetic phase transition. • We obtained all of its critical exponent values: β = 0.164(2) and γ = 0.821(9). • The critical behavior of ErNi 2 is close to the Tricritical mean-field model, but there are still differences. In this article, we analyze the critical behavior of the cubic Laves crystalline binary intermetallic compound ErNi 2 near its second-order ferromagnetic (FM) to paramagnetic (PM) transition (6.9 K). Both the normalized thermal dependencies of the magnetic entropy change curves and the Banerjee criterion confirm the second order nature of the transition. By comparing the normalized slopes, we found that the Tricritical mean-field model is the best model to calculate the critical exponent value of ErNi 2. Based on the modified Arrott plots, the final critical exponents are determined to be β = 0.164(2) and γ = 0.821(9), which are the closest to the Tricritical mean-field model, except for a litter differences. Moreover, the accuracy and reliability of these exponents were confirmed by both the Widom scaling relation and the scaling hypothesis. Our results provide new insight into understanding this compound's magnetic interactions. [Display omitted] [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]

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]

Polycrystalline La 0.825 Sr 0.175 MnO 3 was prepared by solid state reaction method. It exhibits a ferromagnetic–paramagnetic phase transition at T C ∼ 286 K. The intrinsic magnetic properties were clarified by the scaling theory and the isothermal magnetization measured around T C. Based on the modified Arrott plot, Kouvel–Fisher method and Widom relation, the critical exponents are determined to be β = 0. 308 (7) , γ = 1. 065 (8) , δ = 4. 457 (17). Normalization of the critical exponents shows that the extended exchange interaction decays with J ∼ r − 4. 861 , consistent with Tricritical mean field model. Rhodes–Wohlfarth ratio P C / M S >1 suggests that La 0.825 Sr 0.175 MnO 3 is completely itinerant ferromagnet. [Display omitted] • La 0.825 Sr 0.175 MnO 3 shows FM–PM phase transition at 286 K. • Its critical exponents (β = 0.308, γ = 1.065) were determined by the scaling theory. • Its phase transition belongs to Tricritical mean field model. [ABSTRACT FROM AUTHOR]

We present an investigation of Griffiths singularity in La 0.5 Sr 0.5 MnO 3 nanocrystalline by means of magnetic susceptibility and electron paramagnetic resonance (EPR). An unusual platform was found in paramagnetic region. Based on the analysis of EPR spectrum and magnetization variation across the whole temperature range of phase transition, we confirm it is due to the presence of Griffiths singularity rather than a superparamagnetic state in the nanocrystalline system. Such a singularity phase is constituted with some correlated ferromagnetic clusters which embed in paramagnetic matrix. Although they form ferromagnetic spin correlation, the system do not yield any spontaneous magnetization. According to core–shell model, the emergence of Griffiths singularity can be considered due to the presence of local ferromagnetic fluctuations originated from surface spin disorder as the sample size is confined to nanoscale. [ABSTRACT FROM AUTHOR]

In this paper, we reported a detailed study of magnetic properties and magnetic entropy change of nanocrystalline La 0.5 Sr 0.5 MnO 3 . A rigorous measurement of dc magnetization and isothermal magnetization confirm the presence of paramagnetic–ferromagnetic phase transition at 340 K and the formation of spontaneous magnetization in T < T C regime. We found that the obtained magnetic entropy change strongly decreases on reduction of samples size down to nanoscale due to the change of magnetostructural phase transition and magnetic homogeneity. Therefore, the magnetocaloric effect is inevitably tuned by the reduction of particle size. The magnetic phase transition observed in this sample was testified to be second-order by the critical exponent analysis and the systemical magnetic interaction could be understood with mean-field theory. Based on the values of magnetic entropy change under different magnetic fields, we can estimate the spontaneous magnetization which shows an excellent agreement with that deduced from the Arrott curves, indicating that the method to determine spontaneous magnetization with a mean-field analysis of the magnetic entropy change is valid for the material with second order phase transitions. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated the magnetocaloric effect in perovskite manganite Nd 0.55 Sr 0.45 MnO 3 . The maximum magnetic entropy change and the highest relative cooling power under magnetic field variation of 3.0 T are found to be 3.12 J/kg K and 70.87 J/kg, respectively. Based on the obtained magnetic entropy change under different magnetic fields, we have calculated the spontaneous magnetization which persistently increases with the decrease of temperatures. For comparison, the spontaneous magnetization has been also deduced from the Arrott plot. The excellent agreement between the two methods confirms that the utilization of magnetic entropy change to get the spontaneous magnetization is valid. Besides, we also calculated the critical exponent β which value is about 0.452, indicating that the observed ferromagnetic phase transition in the present material can be approximatively understood with mean field model. [ABSTRACT FROM AUTHOR]

Exploring the disorder effect on percolative conductivity is vital to clarify the correlation between magnetism and electronic transport in manganites. By comparing the electronic transports in Nd 0.5 Ca 0.5− x Sr x MnO 3 samples, we find that the increasing disorder changes the magnetic coupling on Mn-site sublattice and broadens the Curie temperature distribution. The electronic transport agrees well with the percolative model in the low disorder sample whereas an obvious discrepancy occurs in high disorder system. The reason is that the percolative channel forms in short temperature range for low disorder sample but a related broad temperature range for high disorder material. [ABSTRACT FROM AUTHOR]

The magnetism and electronic transport properties of $$\hbox {La}_{0.6}\hbox {A}_{0.1}\hbox {Sr}_{0.3}\hbox {MnO}_{3}$$ (A = Sm, Dy, Er) are studied by the measurements of magnetization and resistivity. Infrared spectra reveal that two typical absorbed peaks occur in their corresponding positions. However, the stretching mode $$\nu _{3}$$ exhibits an obvious shift to low frequency and its intensity gets enhanced in Dy- and Er-doping samples. In Raman spectra, the stretching mode shows the same shift, while the Jahn-Teller mode remains invariant. The A-site substitution with other elements changes the average ionic radius and induces cation disorder, causing a decrease of the Curie temperature and the formation of spin-cluster-glass. Except for Sm-doping sample, the field dependence of magnetization at different temperatures shows a similar magnetization process indicating that the low concentration substitution with 10 % magnetic ions cannot signally influence the magnetic exchange interaction on B-site sublattice. Based on the analysis of electronic transport in metallic regime, we find that the main factor for impacting the electronic transport is from the variation of crystal lattice and the induced cationic disorder, regardless of magnetic or non-magnetic substitution. [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]

In this paper, we present a new calculation method of magnetic entropy in an arbitrary second-order ferromagnetic phase transition system. Based on the Arrott-Noakes relation (H/M)1/γ = (T-TC)/TC+(M/M1)1/β, the Gibbs energy can be rewritten as a new form where the critical exponents are naturally included. Correspondingly, the magnetic entropy (SM) is presented as: . Thus, the magnetic entropy change (ΔSM) can be deduced as which is consistent exactly with the previous report [V. Franco et al., Appl. Phys. Lett. 89 (2006) 222512]. In addition, the conventional calculation method of magnetic entropy can be treated as a particular form of this calculation method. Furthermore, the obtained magnetic entropy change from experimental measurement are consistent with the theoretical value deduced from the present method. [ABSTRACT FROM AUTHOR]

Abstract: The dependence of magnetization M on temperature T and the applied magnetic field H were measured for the half-doping manganite Nd0.5Sr0.25Ca0.25MnO3. The M(T) curve exhibits that a paramagnetic (PM)–ferromagnetic (FM) phase transition occurs around 174 K. The PM–FM phase transition is considered to be a second-order phase transition due to the absence of hysteresis on its heating and cooling M(T) curves. Moreover, the second-order phase transition can be testified with the positive slope in Arrott plots. However, the scaling analysis of magnetic entropy change exhibits that ΔS M (T) curves do not collapse into a single universal curve, indicating that the observed PM–FM phase transition is not an authentic second-order phase transition. Due to the appearance of short-range FM coupling in PM region, the PM–FM phase transition at 225 K > T > 188 K is a first-order phase transition. The second-order phase transition only occurs at T < 188 K. When the magnetic field is increased above 1.5 T, the first-order phase transition can be converted into the second-order phase transition. The results shows that the magnetic entropy change scaling is an effective method to determine the nature of the PM–FM phase transition. [Copyright &y& Elsevier]

The doping of bromine has prominent effect on the transport properties of CuCr 2Se 4, where the conductivity of CuCr 2Se 4−xBr x changes from metallic behavior with x=0 to semiconductor with x=1. In this work, the critical behavior of single crystal CuCr 2Se 4−xBr x with x=0.25, which lies at the boundary between the metallic and insulating state, is investigated through the magnetization under high magnetic field. The critical exponents β=0.39±0.03 and γ=1.25±0.05 are obtained by the Kouvel–Fisher method, and δ=4.79±0.01 is generated by the critical iso-thermal analysis. The obtained exponent β is close to the prediction of the three-dimensional (3D) Heisenberg model, while γ approaches that of the 3D-Ising model. Although the bromine doping has prominent effect on the transport behavior, the critical exponents are hardly changed. The obtained results indicate that the ferromagnetism is established through one-dimensional Cr–Se–Cr bonds. However, the nearest-neighbor magnetic interaction belonging to the 3D-Heisenberg model also contributes to the ferromagnetic exchange. [ABSTRACT FROM AUTHOR]

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]

Abstract: The magnetic entropy change () of the spinel selenide CuCr2Se4 has been thoroughly investigated around Curie temperature . It is found that the temperature dependence of under different applied fields H presents a unimodal shape only below 1T, while the full width at half maximum becomes broad with the increase of H. We suggest that the suppression of the spin–orbit coupling between Cr3+ 3d electrons and Se 4p states by the external field should be responsible for the suppression of . In addition, it is displayed that the maximum of depends on H n with obtained by experiment, in agreement with that deduced by the critical analysis. The relative cooling power [RCP(S)] increases with H fulfilling the relation , where a=25.4±0.5J/kgT and b=0.93±0.08. With the scaling laws of , the experimental collapse onto a universal curve, where an average curve is obtained. With the phenomenological universal curve, the experimental are well predicted. [Copyright &y& Elsevier]

Electron paramagnetic resonance studies have been performed on the perovskite manganite Pr0.55Sr0.45MnO3. The various spectrum parameters including line width, effective g-value and double-integrated intensities have been analyzed in detail. The changes of g-value and linewidth are indicative of the presence of strong spin-lattice interaction in the paramagnetic regime. The lattice distortion causes the appearance of localized carriers and the formation of a small polaron. Therefore, the large activation energy obtained from two different methods implies that a strong spin-lattice correlation exists in Pr0.55Sr0.45MnO3. [ABSTRACT FROM AUTHOR]

Abstract: The changes in Raman spectra of graphene flakes after lithography processing are systematically investigated. It is found that substantial changes in the intensity of several Raman peaks are observed after lithography processes involving electron-sensitive and photon-sensitive resists. This finding is related to the generation of disorder and introduction of impurities in the graphene flakes. It is observed that the disorder induced after spin coating PMMA resist on the graphene flakes cannot be removed by acetone but can be eliminated by means of an annealing process. The use of the AZ6624 photo-sensitive resist produces Raman changes typical for amorphization. When using this resist, the disorder-induced changes in the Raman spectra persist even after the same annealing process, implying that the contamination caused by the used photo-sensitive resist is more difficult to eliminate. The present results emphasize the important role played by the lithography process, often taken for granted, in the physical properties of graphene. [Copyright &y& Elsevier]

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]

Abstract: In the present work, the magnetic entropy change of the half-doped Nd0.5Ca0.25Sr0.25MnO3 manganite has been investigated. The measurement of isothermal magnetization around Curie temperature reveals the maximum isothermal magnetic entropy change of 1.85 and 0.77J/kgK for and 1.0T magnetic field variation, respectively. In addition, from the data of heat capacity, we find the adiabatic temperature change of 0.88K for a magnetic field variation of 3.0T. Though only a moderate magnetic entropy change and a small adiabatic temperature change were obtained, a considerable large relative cooling power (140J/kg as ) and a wide temperature range (74K as ) were found in this sample, this ensure it to be a promising candidate for the actual magnetic refrigerant materials. [Copyright &y& Elsevier]

Abstract: The magnetism and electronic transport properties in the manganites have been studied. The doped sample provides a good system to detect the impurity effect in charge ordering materials due to a fixed ratio of . We find that the induced ferromagnetism stems from the exchange couple between the magnetic impurity and Mn element. The local charge ordering phase forms an antiferromagnetic coupling whereas its intensity weakens with the decrease of temperature. In the high temperature region, the electronic transport occurs in the variable-range hopping manner. [Copyright &y& Elsevier]

Abstract: In this paper, the magnetocaloric effect of perovskite manganite has been investigated. From the measurement of isothermal magnetization around the Curie temperature, we have calculated the maximum isothermal magnetic entropy change as 3.14J/kgK for the 1.5T magnetic field variation. Furthermore, a large relative cooling power of 45J/kg has been determined, which makes attractive candidate materials for magnetic refrigeration. [Copyright &y& Elsevier]

Abstract: The magnetic properties of Nd0.6Ln0.1Sr0.3MnO3 compositions (Ln = La, Pr, Gd, Dy) have been investigated thoroughly. The effect of is considered to be profound on the PM–FM phase transition in the manganites. The experiment results indicate that decreases with Ln changing from La to Gd due to the decreases of . The abnormal increase of in Dy-composition with the smallest and largest is attributed to the large magnetic moment of Dy3+ ions. The rapid increase of magnetization below 30 K indicates directly the magnetic ordering of rare earth ions at A-site. [Copyright &y& Elsevier]

Abstract: The structural, magnetic, and transport properties of the polycrystalline-doped systems Nd0.7Sr0.3Mn1−x Ga x O3 () were investigated. For the parent and low-doped samples (), they show a long-range ferromagnetic state below and the Griffiths singularity above . When further exceeds 0.12, a transition from the metal ferromagnetic to the insulating cluster-spin-glass state as a function of Ga doping takes places at low temperatures. is just a critical point transforming from the Griffiths singularity to the cluster-spin-glass state. [Copyright &y& Elsevier]

Abstract: The electrical and magnetic properties of highly doped manganite Gd0.4Ca0.6MnO3 with a relatively small have been investigated thoroughly. Through the , , and ESR measurements it is found that the magnetization in curve originates from the paramagnetic contribution of disordered Mn ions at B-site and Gd3+ ions at A-site. The peculiar behavior of curve below TCO originates from the remaining spin disordered Mn ions after the formation of charge-ordering phase in the manganite, and the AFM charge-ordering state is supposed to be a local short-range ordering state. [Copyright &y& Elsevier]

Abstract: The transport properties and magnetic phase transitions of charge ordering manganites Nd0.5Sr0.5MnO3 have been investigated. From resistivity measurements, a continuous increase of resistivity upon the thermal cycling occurs at , and shows an instable behavior in the system. The experimental results of magnetization and electron-spin-resonance spectra indicate that the ferromagnetic phase and antiferromagnetic phase coexist in a broad temperature region. We think that the origin of the instability stems from an inhomogeneous strain yielded in the ferromagnetic interface, due to the competition among different phases. [Copyright &y& Elsevier]

Abstract: The magnetic phase transition and insulating-metal phase transition in the charge ordering (CO) Nd0.51Ca0.49Mn0.98Cr0.02O3 system have been studied. From the magnetization and resistivity measurements, a considerable instability is observed in the temperature region upon thermal cycle. In the thermal hysteresis region, both antiferromagnetic (AFM) and paramagnetic (PM) phases transform into ferromagnetic (FM) phase as the temperature decreases, thus the strong ferromagnetism emerges in the system. The origin of the instability should be attributed to the strain relaxation in the interfacial region. Interestingly, due to the growing FM interaction, the AFM coupling becomes weakened rather than strengthened at low temperatures. [Copyright &y& Elsevier]

Abstract: The magnetic and transport properties in the perovskite Sr1− x La x Fe1− x Mn x O3 have been explored. As x rises, the systemic ferromagnetism increases gradually and cluster-spin-glass state occurs in the low-temperature region. For 0.3⩽x⩽0.7, the ferromagnetic phase separation from the paramagnetic phase was observed from the results of electron-spin-resonance measurement. Although all samples show a semiconducting behavior, their transport properties are dominated by two different mechanisms, namely, the electronic transport of x⩽0.5 samples is realized by thermal activation but the variable-range hopping is applied in x⩾0.7 ones. The different transport mechanism can be understood from the Mn/Fe ions interaction. [Copyright &y& Elsevier]

Abstract: The magnetic property of double doped manganite Nd0.5(1+x)Ca0.5(1−x)Mn(1−x)Cr x O3 with a fixed ratio of Mn3+:Mn4+=1:1 has been investigated. For the undoped sample, it undergoes one transition from charge disordering to charge ordering (CO) associated with paramagnetic (PM)-antiferromagnetic (AFM) phase transition at T<250K. The long range AFM ordering seems to form at 35K, rather than previously reported 150K. At low temperature, an asymmetrical M–H hysteresis loop occurs due to weak AFM coupling. For the doped samples, the substitution of Cr3+ for Mn3+ ions causes the increase of magnetization and the rise of T c. As the Cr3+ concentration increases, the CO domain gradually becomes smaller and the CO melting process emerges. At low temperature, the FM superexchange interaction between Mn3+ and Cr3+ ions causes a magnetic upturn, namely, the second FM phase transition. [Copyright &y& Elsevier]

Abstract: The magnetic phase transition and insulator–metal phase transition in charge ordering Nd0.50Sr0.45Ca0.05MnO3 system have been studied. As the temperature decreases below 100 K, the antiferromagnetic coupling becomes stronger but the ferromagnetic phase basically remains unchanged. At low temperature, the ferromagnetic and antiferromagnetic phases coexist in the system. From the measurement of magnetization and resistance with thermal cycling, a considerable instability is observed at . The phase competition is responsible for the presence of instability. [Copyright &y& Elsevier]

We have studied the evolution of Griffiths phase and the magnetic ordering state in the intermetallic compound LaCeCo 7. A ferromagnetic-like ordering phase is built up at 260 K but an anomalous magnetic susceptibility related to the Griffiths phase occurs in 300 K. The studies of critical behavior confirm that LaCeCo 7 exhibits a second-order paramagnetic-ferromagnetic phase transitions. The critical exponents of β = 0.665, γ = 1.151, and δ = 2.728 determined by the magnetic field dependence on magnetic entropy change method deviate a little from the theoretical estimated long-range mean-field model (β = 0.5, γ = 1.0, and δ = 3.0). This result implies that the disorder effect in the intermetallic LaCeCo 7 possibly plays a key role on the anomalous critical behavior and the establishment of magnetic ordering phase. [ABSTRACT FROM AUTHOR]

Real-time monitoring of structural health status is very important for supersonic aircraft, since the long-term operation in harsh service environments, such as high temperatures, can cause potential damage. Structural health monitoring (SHM) based on lamb wave has been approved to be a critical technique for the reliable operation of supersonic aircraft, but is limited by the operating temperature of conventional piezoelectric sensors, which makes it difficult to meet the high-temperature monitoring requirements. The BiFeO 3 –BaTiO 3 ceramics exhibit excellent piezoelectric properties and high Curie temperature (T c), making them promising for high-temperature SHM of supersonic aircraft. Here, we fabricated a piezoelectric sensor using 0.67BiFeO 3 -0.33BaTiO 3 -0.25%molMnO 2 (BF33BTMN-025) ceramic, which exhibits a piezoelectric charge constant (d 33) of 135 pC/N at room temperature and a T c of 448 °C. The BF33BTMN-025 ceramic sensor operates effectively at temperatures up to 200 °C and maintains stable damage monitoring sensitivity as well. Compared with Pb(Zr, Ti)O 3 (PZT), BaTiO 3 (BTO) and other piezoelectric sensors commonly used in SHM field, the BF33BTMN-025 ceramic sensor has a higher operating temperature and a comparable sensitivity. Our work demonstrates that the BF33BTMN-025 ceramic sensor can be employed as piezoelectric sensor for high-temperature SHM, which has a wide application potential in the field of real-time monitoring of supersonic aircraft. [ABSTRACT FROM AUTHOR]