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1.
A. Ezaami E. Sellami-Jmal W. Cheikhrouhou-Koubaa M. Koubaa A. Cheikhrouhou 《Journal of Superconductivity and Novel Magnetism》2017,30(4):911-916
In this work, we studied in detail the magnetic and magnetocaloric properties of the La0.7Ca0.2Ba0.1MnO3 compound according to the phenomenological model. Based on this model, the magnetocaloric parameters such as the maximum of the magnetic entropy change ΔS M and the relative cooling power (RCP) have been determined from the magnetization data as a function of temperature at several magnetic fields. The theoretical predictions are found to closely agree with the experimental measurements, which make our sample a suitable candidate for refrigeration near room temperature. In addition, field dependences of \({{\Delta } S}_{\mathrm {M}}^{\max }\) and RCP can be expressed by the power laws \({\Delta S}_{\mathrm {M}}^{\max }\approx a\)(μ 0 H) n and RCP ≈b(μ 0 H) m , where a and b are coefficients and n and m are the field exponents, respectively. Moreover, phenomenological universal curves of entropy change confirm the second-order phase transition. 相似文献
2.
Calcium-substituted lanthanum manganite compounds were synthesized by the spray drying technique. This method—whose main advantages are versatility, high reproducibility and scalability—yields small grain materials of high homogeneity and displaying low-field magnetoresistance effects. We report about the physical and chemical characterizations of these samples in order to investigate the potential interest of spray drying for the production of materials for low-field magnetoresistance applications. We have studied the dependence of the low-field magnetoresistance on the temperature and duration of the thermal treatment applied to the pelletized powders. The issue of the shape anisotropy (demagnetisation effects) influence on the magnetoresistance properties has also been dealt with. 相似文献
3.
F. C. Fonseca J. A. Souza E. N. S. Muccillo R. Muccillo R. F. Jardim 《Journal of Materials Science》2008,43(2):503-509
The physical properties of the La0.6Y0.1Ca0.3MnO3 compound have been investigated, focusing on the magnetoresistance phenomenon studied by both dc and ac electrical transport
measurements. X-ray diffraction and scanning electron microscopy analysis of ceramic samples prepared by the sol–gel method
revealed that specimens are single phase and have average grain size of ∼0.5 μm. Magnetization and 4-probe dc electrical resistivity
ρ(T,H) experiments showed that a ferromagnetic transition at T
C
∼ 170 K is closely related to a metal-insulator (MI) transition occurring at essentially the same temperature T
MI
. The magnetoresistance effect was found to be more pronounced at low applied fields (H ≤ 2.5 T) and temperatures close to the MI transition. The ac electrical transport was investigated by impedance spectroscopy
Z(f,T,H) under applied magnetic field H up to 1 T. The Z(f,T,H) data exhibited two well-defined relaxation processes that exhibit different behaviors depending on the temperature and applied
magnetic field. Pronounced effects were observed close to T
C
and were associated with the coexistence of clusters with different electronic and magnetic properties. In addition, the
appreciable decrease of the electrical permittivity ε′(T,H) is consistent with changes in the concentration of e
g
mobile holes, a feature much more pronounced close to T
C
. 相似文献
4.
R. Skini M. Khlifi E. Dhahri E. K. Hlil 《Journal of Superconductivity and Novel Magnetism》2017,30(11):3091-3095
This investigation is interested in studying the relation between magnetocaloric effect and transport properties i La0.8Ca0.2MnO3 manganite compound. The value of the magnetocaloric effect has been determined from the calculation of magnetization as a function of temperature under different external magnetic fields. This study also provides an alternative method to determine the magnetocaloric properties such as magnetic entropy change and heat capacity change on the basis of M(T, H) measurements. On the other hand, based on magnetic and resistivity measurements, the magnetocaloric properties of this compound were investigated using an equation of the form \({\Delta } S \,=\, - \alpha {\int \limits _{0}^{H}} {\left [ {\frac {\delta Ln\left (\rho \right )}{\delta T}} \right ]}_{H} dH\), which relates magnetic order to transport behavior of the compounds. As an important result, the values of MCE and the results of calculation are in good agreement with the experimental ones, which indicates the strong correlation between the electric and magnetic properties in manganites. 相似文献
5.
E. Restrepo-Parra G. Orozco-Hernández J. Urrea-Serna J. F. Jurado J. C. Vargas-Hernández J. C. Riaño-Rojas J. Restrepo 《Journal of Materials Science》2010,45(24):6763-6768
A Monte Carlo simulation study of La2/3Ca1/3MnO3/La1/3Ca2/3MnO3 bilayers exchange bias (EB) properties by using a classical Heisenberg model and Monte Carlo method with Metropolis algorithm
is addressed. Samples were built atom-by-atom in order to resemble the real roughness. In this model, several contributions
included nearest neighbors exchange interactions; two different interface couplings, magnetocrystalline anisotropy and Zeeman
term, were considered. Here, an influence of the relaxation steps on the interface roughness is present. Our study focuses
on the influence of interface roughness on hysteresis loops, particularly EB field (H
ex) and coercive force (H
c). Results reveal that H
ex and H
c decrease as the interface roughness increases. 相似文献
6.
S. V. Trukhanov 《Technical Physics Letters》2011,37(4):350-353
It is established that the magnetic state of the anion-deficient La0.70Sr0.30MnO2.85 manganite represents the spin-glass state of the cluster. The magnetic field at the beginning (H < 10 kOe) leads to the fragmentation of ferromagnetic clusters, then (H > 10 kOe) leads to the transition to a ferromagnetic state of an antiferromagnetic matrix and to increase in the degree of
polarization of local spins of manganese. It is determined that the freezing temperature of magnetic moments varies as T
f
= 65 − 6H
0.21. The causes and mechanism of the magnetic phase separation are discussed. 相似文献
7.
Liqin Yang Xinsheng Yang Li Lv Cuihua Cheng Yong Zhao 《Journal of Superconductivity and Novel Magnetism》2011,24(6):1847-1851
A novel boned perovskite manganese oxide magnetoresistant material was prepared using La0.7Sr0.3MnO3 (LSMO) as the precursor powders and metal tin (Sn) as the binder. The microstructure and phase characteristics, low-field
transport properties were studied. Sn segregated at the grain boundaries of LSMO grains. The insulator–metal (I–M) transition and enhanced LFMR are only observed with a low content of Sn, due to grain boundary disorder and spin polarized
tunneling between grain boundaries. The Sn addition induced resistivity decreasing dramatically. In the high temperature PM
region, the resistivities for samples with low Sn content follow the adiabatic small-polaron-hopping model. 相似文献
8.
K. Riahi I. Messaoui W. Cheikhrouhou-Koubaa S. Mercone B. Leridon M. Koubaa A. Cheikhrouhou 《Journal of Superconductivity and Novel Magnetism》2017,30(8):2081-2089
The La0.78Dy0.02Ca0.2MnO3 (LDCMO) compound prepared via high-energy ball-milling (BM) presents a ferromagnetic-to-paramagnetic transition (FM-PM) and undergoes a second-order phase transition (SOFT). Based on a phenomenological model, magnetocaloric properties of the LDCMO compound have been studied. Thanks to this model, we can predict the values of the magnetic entropy change ΔS, the full width at half-maximum δ T FWHM, the relative cooling power (RCP), and the magnetic specific heat change ΔC p for our compound. The significant results under 2 T indicate that our compound could be considered as a candidate for use in magnetic refrigeration at low temperatures. In order to further understand the FM-PM transition, the associated critical behavior has been investigated by magnetization isotherms. The critical exponents estimated by the modified Arrott plot, the Kouvel–Fisher plot, and the critical isotherm technique are very close to those corresponding to the 3D-Ising standard model (β = 0.312 ± 0.07, γ = 1.28 ± 0.02, and δ = 4.80).Those results revealed a long-range ferromagnetic interaction between spins. 相似文献
9.
S. A. Solopan O. I. V’yunov A. I. Tovstolytkin L. L. Kovalenko A. G. Belous 《Inorganic Materials》2007,43(11):1252-1257
La0.775Sr0.225MnO3 films have been produced by screen printing on various substrates (Al2O3, BaTi0.85Zr0.11Sn0.04O3, Ba0.996Y0.004TiO3, Ba0.996Y0.004TiO3 + 0.04%Mn, and Ba0.996Y0.004Ti0.65Sn0.35O3), and their electrical properties have been studied in comparison with those of bulk materials. The structural properties of the substrates are shown to influence the electrical properties of the films. 相似文献
10.
Vaneet Sharma Maria R. Hossu Woo Ho Lee Ali R. Koymen Shashank Priya 《Journal of Materials Science》2007,42(23):9841-9844
This letter reports the effect of the A-site doping (2, 4, and 6 mol% Bi and Li) on the piezoresistance phenomenon in La0.8Sr0.2MnO3 (LSMO) polycrystalline ceramics. The fractional change in resistivity was found to be nominal for Li-modified samples but
samples modified with 4 and 6 mol% Bi2O3 exhibited 1.8% and 2.3% fractional change in resistivity
at 19.2 MPa which is significantly higher than that for pure LSMO. The enhancement in piezoresistive phenomenon is attributed
to distortion of Mn–O bond due to substitution of smaller ion on to La-site. All the samples showed a sudden increase in resistivity
with applied stress in the range of 0.5–2 MPa and the behavior was found to saturate as the magnitude of applied stress increases.
Magnetic measurements as a function of field and temperature were conducted to confirm the A-site substitution. 相似文献
11.
Diluted samples of La0.8Sr0.2MnO3 with SiO2 were prepared by calcination of the MCM-41 molecular sieve soaked in precursor solutions with various concentrations (0.1, 0.05 and 0.005 mol/l). The diluted samples from the 0.1, 0.05 and 0.005 mol/l solutions showed ferromagnetic behavior in temperature dependent magnetic susceptibility below 300, 250 and 100 K, respectively. The electron binding energy of the La 3d5/2 main peak of the diluted samples from the 0.1, 0.05 and 0.005 mol/l solutions were 835.7, 836.0 and 837.4 eV, respectively, and were larger than that of La0.8Sr0.2MnO3 bulk sample (834.2 eV). Reduction in intensity of the La 3d charge-transfer satellite was more pronounced for more diluted sample. The Mn 2p3/2 main peak of all the diluted samples remained at 642.2 eV, which is larger by 0.6 eV than that of the bulk sample (641.6 eV). The charge-transfer peak energy in the optical absorption spectra was the same (2.3 eV) for all the diluted samples, and the energy was larger by 0.4 eV than the bulk one (1.9 eV). The dilution caused localization of charge carriers within the La0.8Sr0.2MnO3 lattices isolated by the insulator. Suppression of charge flow between the isolated La0.8Sr0.2MnO3 lattices resulted in the enlargement of the La 3d electron binding energy and the decrease of the La 3d charge-transfer satellite peak intensity, and also the lowering of the ferromagnetic ordering temperature. © Springer Science + Business Media, Inc. 相似文献
12.
A. Krichene R. Thaljaoui W. Boujelben 《Journal of Superconductivity and Novel Magnetism》2015,28(7):1881-1885
We have inspected the magnetic properties of polycrystalline La0.4Bi0.1Ca0.5MnO3 using electron spin resonance (ESR) in the temperature range 150–280 K. The temperature dependence of magnetization indicates that the Curie temperature is T C= 225 K. ESR spectra revealed that the sample is not completely paramagnetic above its Curie temperature through the presence of ferromagnetic interactions in the temperature range 225–270 K which can be attributed to the presence of Griffiths phase in this temperature range. The sample becomes completely paramagnetic above 270 K. The presence of Griffiths phase can be attributed to the disorder induced by the 6 s 2 lone pair electrons of Bi3+ ions. 相似文献
13.
Epitaxial trilayer heterostructures of the type La0.67Ca0.33MnO3/SrTiO3/La0.67Ca0.33MnO3 were grown by laser ablation on (001)[(LaAlO3)0.3+(Sr2AlTaO6)0.7] substrates. The real part of the dielectric permittivity ε and the loss factor tan δ of a 1100-nm-thick SrTiO3 interlayer were studied in the temperature interval T=4.2–300 K in a nonbiased state and at a bias voltage of ±2.5 V applied to the manganite electrodes. Using the temperature dependence ε(T) measured for the SrTiO3 layer grown between the manganite electrodes, we have estimated the capacitance of La0.67Ca0.33MnO3/SrTiO3 interfaces (C1≈2 μF/cm2) related to the electric field penetrating from the interlayer into La0.67Ca0.33MnO3. 相似文献
14.
A systematic investigation of photoinduced properties is carried out in La0.67Ca0.33MnO3 film prepared on LaAlO3 (100) substrate by magnetron sputtering method. At T < 270 K, the resistivity of film induced by laser increases because of the demagnetization effect of manganites. The photoinduced
relaxation character of film indicates that the time constant increases with increasing temperature, which is attributed to
the growing thermal fluctuation. After laser irradiation, the resistivity returns to the original value and the relaxation
time seems to be independent of temperature. In insulating state, laser irradiation induces the reduction in resistivity of
film due to the excitation of small polarons. 相似文献
15.
Rashmi Yadav Avneesh Anshul Vilas Shelke 《Journal of Materials Science: Materials in Electronics》2011,22(8):1173-1180
We report observation of composition and process parameter dependant wide range magnetoresistance and high temperature coefficient
of resistance in La0.7Sr0.3−xAgxMnO3 (0 ≤ x ≤ 0.3) system. The polycrystalline samples synthesized through solid state reaction method exhibited rhombohedral
structure with systematic change in lattice parameters. The samples with x ≤ 0.2 showed metallic behavior below room temperature.
A broad metal-insulator transition is observed for x = 0.3, which becomes sharp for the samples sintered at high temperature.
The broad transition resulted in magnetoresistance (MR) value around 35% over a wide temperature range whereas the sharp transition
results in MR value as high as 85%. The temperature coefficient of resistance value of 11% is seen as a consequence of sharp
transition. The magnetic transition was sharp for the samples sintered at high temperature. 相似文献
16.
G. S. Patrin K. P. Polyakova T. N. Patrusheva D. A. Velikanov 《Technical Physics Letters》2007,33(4):330-332
We have experimentally studied the magnetic properties of manganite films obtained for first time using an extraction-pyrolysis technique. It is established that the characteristics of samples significantly depend on the conditions of final annealing. The annealing at temperatures T a < 970 K is accompanied by strong thermomagnetic effects, and the resulting films possess properties similar to those of spin glasses. When the annealing temperature is increased to T a ≥ 1020 K, the films exhibit magnetic properties typical of ferromagnetic systems. 相似文献
17.
S. S. Chen C. P. Yang C. L. Ren R. L. Wang H. Wang I. V. Medvedeva K. Baerner 《Bulletin of Materials Science》2011,34(4):793-798
Interface-dependent electric-pulse-induced resistance switching effect (EPIR) in Nd0.7Sr0.3MnO3 ceramics was studied. The results reveal that the EPIR effect originates from the interface between the electrodes and the
bulk, and the EPIR ratio as well as the high and low resistance states can be strongly influenced by applying a large electrical
field on the sample for different intervals. Also, the pulse parameters have great effect on the stability of EPIR and the
optimal pulse width, pulse amplitude and read bias are obtained. Based on the space charge limited current mechanism together
with the theory of interfacial charge-trapped state, the interface-dependent resistance switching effect is discussed. 相似文献
18.
We report the results of magnetic, magnetocaloric properties, and critical behavior investigation of the double-layered perovskite manganite La1.4(Sr0.95Ca0.05)1.6Mn2O7. The compounds exhibits a paramagnetic (PM) to ferromagnetic (FM) transition at the Curie temperature T C = 248 K, a Neel transition at T N = 180 K, and a spin glass behavior below 150 K. To probe the magnetic interactions responsible for the magnetic transitions, we performed a critical exponent analysis in the vicinity of the FM–PM transition range. Magnetic entropy change (??S M) was estimated from isothermal magnetization data. The critical exponents β and γ, determined by analyzing the Arrott plots, are found to be T C = 248 K, β = 0.594, γ = 1.048, and δ = 2.764. These values for the critical exponents are close to the mean-field values. In order to estimate the spontaneous magnetization M S(T) at a given temperature, we use a process based on the analysis, in the mean-field theory, of the magnetic entropy change (??S M) versus the magnetization data. An excellent agreement is found between the spontaneous magnetization determined from the entropy change [(??S M) vs. M 2] and the classical extrapolation from the Arrott curves (µ0H/M vs. M 2), thus confirming that the magnetic entropy is a valid approach to estimate the spontaneous magnetization in this system and in other compounds as well. 相似文献
19.
V. T. Dovgii A. I. Linnik V. I. Kamenev V. K. Prokopenko V. I. Mikhailov V. A. Khokhlov A. M. Kadomtseva T. A. Linnik N. V. Davydeiko G. G. Levchenko 《Technical Physics Letters》2008,34(12):1044-1046
Chaotic oscillations of the low-frequency magnetic susceptibility χ in a Nd0.5Sr0.5MnO3 (NSMO) manganite single crystal have been observed in the temperature interval of the coexistence of the ferro- and antiferromagnetic
phases of the given composition. It is established that the amplitude of χ oscillations depends on the constant bias magnetic
field. The appearance of susceptibility oscillations in NSMO single crystals is attributed to the formation of magnetic transition
regions, which can exist at the boundaries between ferro- and antiferromagnetic phases. 相似文献
20.
H. X. Liu C. B. Wang L. Wu L. Yin L. Li Q. Shen L. M. Zhang 《Journal of Materials Science》2018,53(4):2375-2382
Different components of La0.7?x Ho x Sr0.3MnO3 (LHSMO, x = 0, 0.1, 0.2, 0.3) ceramics were fabricated by Plasma-Activated Sintering (PAS), so as to study the correlation between the contents of Ho3+ and the structural, electrical, magnetic properties. XRD and SEM confirmed that LHSMO ceramics prepared by PAS exhibited high-purity phase and dense microstructure. The measurement of electrical resistivity showed that the resistivity of LHSMO ceramics increased, and the metal–insulator transition temperature decreased with the increasing Ho-doping content. The resistivity data were then fitted using various empirical equations, and the conduction mechanism of LHSMO ceramics was found to be in accord with the electron–magnon scattering process in the low-temperature region and the small polaron hopping model in the high-temperature region. Lastly, we calculated the values of magnetoresistance of the LHSMO ceramics, which increased with increasing Ho-doping content, from 3.5% for x = 0 to 14.6% for x = 0.3. Therefore, the doping of Ho3+ into La0.7Sr0.3MnO3 can effectively enhance the low-field magnetoresistance effect. 相似文献