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Temperature dependent resistivity for La0.67–xRExCa0.33MnO3(RE = Nd, Sm, and Gd, x = 0.0, 0.1) samples at (a) zero field and (b) at 9 T applied magnetic field.
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We investigated the influence of 10% substitution of rare-earth (RE) elements on the crystallographic, transport, and magnetic properties of La 0.67– x RE x Ca 0.33 MnO 3 (RE = Nd, Sm, and Gd, x = 0.0, 0.1) manganite perovskite compounds. The bulk polycrystalline samples were synthesized using solid-state reaction method. The phase purity and cryst...
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La0.68−xAxCa0.32MnO3, where A = Y, Gd (x = 0.00, 0.08) have been studied by XRD, Magnetoresistance amplitude measurement and SEM (Scanning Electron Microscopy) grain size determination, magnetic measurement of x = 0.00. The bulk sample was prepared by the solid state reaction method (standard ceramic technique) between the corresponding metallic ox...
Citations
... Despite several studies focusing on nickel-doped lanthanum ferrites, there is a lack of information about the effect of substitution of Ni 2+ in the magnetic and electric behavior of bulk LFO, which could extend the range of technological applications. Additionally, high-energy ball milling has been reported to enhance solid solubility in similar ferrites and, promotes high levels of strain, which could modify the magnetic structure of the LFO [36,37]. ...
... The effect of co-doping with two cations has been also studied, with improvements in ferroelectric and ferromagnetic properties, such as those shown by studies focused on double substitution with Dy-Ti [31], Dy-Mn [28], Gd-Nb [32], Sr-Co [43], and Ca-Co [27], in which the antiferromagnetic spin structure of LFO is changed to the most favorable ferrimagnetic spin structure. Among others cations, the substitution of Fe 3+ by Ni 2+ in LFO, which have different magnetic moments (2.8 µB and 5.9 µB) and different ionic radii (0.69 Å and 0.645 Å), respectively [41], can modify the magnetic structure of LFO from the AFM to FM order, as has been demonstrated in similar ferrites [9], attributed to two main factors: (i) the presence of uncompensated spins and, (ii) a tilting of the interstitial octahedral sites due to a slight structural distortion produced by the substitution, which could reduce the AFM superexchange interactions and in turn, modify the bandwidth (W) [37], promoting the ferromagnetic double exchange. However, Ni 2+ with a lower oxidation state will generate oxygen vacancies as a charge compensation mechanism, so an increment in dielectric losses, conductivity and consequently, in the leakage currents density of the material is expected. ...
... Using the data obtained from the refinement, the Fe-O-Fe bond angles are estimated using VESTA (Visualization for Electronics and Structural Analysis) software [33], and the bandwidth values are calculated using the following empirical expression [37]:ẁ here W is the bandwidth, ω is the Fe-O-Fe bond angle, and d Fe-O is the Fe-O bond distance. ...
In this research, LaFeO3 doped with different concentrations of Ni²⁺ at Fe sites, ranging from 0.1 to 0.5 with a Δx of 0.1, was studied. The synthesis process involved high-energy milling followed by heat treatment at a low temperature, 1073 K, to induce ferromagnetic order (FM). Moreover, the effects of cation doping on the crystal structure and multiferroic properties were determined. X-ray diffraction analysis and Rietveld refinement confirmed that doped lanthanum ferrite with an orthorhombic structure (Pnma) was obtained for all the studied dopant levels. The magnetic hysteresis loops change from antiferromagnetic (AFM) to weakly ferromagnetic at room temperature when Ni²⁺ is introduced into the LaFeO3 crystal structure, which is attributed to spin canting due to the difference in ionic radius between the Fe³⁺ and Ni²⁺ cations and to the frustration of the magnetic cycloid due to the existence of uncompensated ions. Regarding the dielectric properties, the doped ferrites show semiconductor behavior with high values of relative permittivity as the doping concentration increases. XPS spectra confirmed the existence of adsorbed oxygen associated with oxygen affinity as a mechanism of charge compensation due to vacancies and oxidation from Fe³⁺ to Fe⁴⁺.
... In addition, the Mn-O bond length exhibited a slight increase, which modified the electron bandwidth (W), which is the hopping distance of the itinerant electron. The bandwidth included in Table 1 was calculated with the following expression [25]: ...
An analysis of the sensitivity of the electrical resistance to temperature changes in cobalt-doped lanthanum-strontium manganite was carried out to provide new insight into the effects of the magnetic interactions between cobalt and manganese ions on the electric properties. Cobalt-doped lanthanum-strontium manganites, La0.7Sr0.3CoxMn1−xO3 with x ranging from 0 to 0.1 (Δx = 0.025), were synthesized by high-energy ball milling for 5 h, followed by annealing at 1673 K. X-ray diffraction showed the presence of a rhombohedral phase for all the studied compositions, indicating a decrease in the bandwidth as the cobalt content increased. The Curie temperature, determined by vibrating sample magnetometry, and the insulator-metal transition temperature, determined by electrical measurements, decrease near to room temperature with increases cobalt content up to 0.1 by weakening the double exchange magnetic interaction. The results confirmed that cobalt increased the temperature coefficient of resistance for the doped manganites by up to 15.6% for 0.1 mol of cobalt near room temperature. Therefore, these materials will prove useful for the development of specialized sensing devices such as bolometers.
... Our analysis suggests that the electrical transport mechanism is governed by the thermal activation model, also known as Arrhenius law. According to Arrhenius law, the conductivity variation with temperature follows the following relationship [60], ...
In this study, we report the structural, hardness, optical, and high temperature thermoelectric properties of Gd-doped lanthanum cobaltite La1−xGdxCoO3 (x = 0.0, 0.2, 0.4, 0.6). The samples have been prepared by solid-state reaction technique. The room temperature XRD studies revealed that the pristine sample (x = 0.0) possesses a distorted rhombohedral structure with an R-3c space group. The samples with x ≥ 0.2 show a structural phase transition and possess an orthorhombic structure with the Pnma space group. Structural and optical studies confirm the formation of the La1-xGdxCoO3 compound. The electrical re- sistivity for all the studied compositions is found to be inversely proportional to temperature, which is a typical semiconductor behavior. However, the electrical resistivity was found to increase with increased Gd content in the material. The pure and Gd substituted samples show a crossover from negative to positive thermopower, thereby indicating the presence of both electrons and holes as charge carriers. The sub- stitution of Gd has enhanced the thermopower at high temperatures. The highest thermopower of –345 μV/ K was obtained at 310 K for the pristine sample. A significant drop in electrical resistivity (T > 400 K) has caused the power factor to rise, resulting in a higher power factor of 141 µW/mK2 for the sample x = 0.4 at 755 K
... K) [16], indicating La 1-x (Ca, Sr) x MnO 3 is a kind of ideal candidate for highly sensitive bolometer with room-temperature. However, the TCR of perovskite manganites films is in general much lower than that of bulk materials at present, and this is mainly caused by poor crystallinity [17][18][19][20][21][22][23][24]. For instance, La 0.67 Ca 0.33 MnO 3 films had a different surface morphology compared with La 0.67 Ca 0.33 MnO 3 ceramics [25,26], which was caused by different crystallinity induced by lower sintering temperature and shorter sintering time. ...
... The mismatch of radii at the A-site substitution causes chemical pressure, which leads to random lattice disorder and changes the tolerance factor t = distance, and Mn-O-Mn angles. As a result, a variation of structural and magnetic properties occurs [14][15][16][17][18][19]. La 1-x Pb x MnO 3 manganites are the materials of interest in this study. ...
Direct and indirect measurements of the magnetocaloric effect in La0.7Pb0.3-xBaxMnO3 (x = 0.05, 0.10, and 0.15) manganite were reported. The effect of Pb substitution with Ba on the structural, magnetic, and magnetocaloric properties of these compounds was investigated. The X-ray analysis reveals a structural transition upon doping. The rhombohedral structure of x = 0.05 is transformed into a mixture of cubic and rhombohedral phases for both samples x = 0.10 and x = 0.15. For all the samples, magnetic versus temperature analysis shows a transition from a paramagnetic (PM) to a ferromagnetic state (FM). The zero-field heat capacity measurement was also performed. The magnetocaloric efficiency was determined from adiabatic temperature and isothermal magnetization curves using Maxwell relation. It is found that the sample with the composition x = 0.10 exhibits the highest value of ΔTad and ΔSm which were found to be 1.75 K and 1.445 Jkg−1 K−1 at 3 T respectively. The corresponding relative cooling power (RCP) was around 145.5 Jkg−1. The phenomenological construction of the universal curves and the Banerjee criterion revealed a second-order phase transition for all samples.
... The sol-gel process is preferred by several researchers because of its short reaction time, fine particle size, and low sintering temperature [19,20]. Some studies have demonstrated the relationship between La 1-x Sr x MnO 3 and La 1-x Ca x MnO 3 , with the former exhibiting a higher T k and lower TCR and the latter exhibiting the contrary [21][22][23][24]. For instance, La 1-x Sr x MnO 3 exhibited the highest TCR of 2.95% K -1 and T k of 339.26 ...
... K at x = 0.2 [21]. The TCR of polycrystalline La 1-x Ca x MnO 3 ceramics reached a maximum value of 7% K -1 and T k was 270 K at x = 0.33 [22]. However, these materials are still inadequate for practical application in infrared devices. ...
... K. In comparison to previous studies, the highest values were reached at room temperature for La 0.67 Sr 0.10 Ca 0.13 K 0.10 MnO 3 perovskite [21,22,25,28]. Unlike the peak of TCR, T k increases continuously with increasing Sr doping, which is similar to T p . ...
Current research on perovskite materials is mainly focused on how to achieve a high temperature coefficient of resistivity (TCR) in anticipation of application in infrared detection. In this study, we report the superior electrical transport properties of polycrystalline La0.67SrxCa0.23-xK0.1MnO3 (LSCKMO) (0.03 ≤ x ≤ 0.13) ceramics produced through the sol-gel process using different Sr doping contents. Based on previous studies, polycrystalline manganite ceramics with a higher TCR at room temperature were obtained by optimising the composition ratio of Sr or Ca. In the process of continuous doping, the crystal structure of the polycrystalline LSCKMO ceramics changed significantly from Pnma to R 3¯ c. The final polycrystalline La0.67Sr0.10Ca0.13K0.1MnO3 ceramic material was obtained with a TCR of 17.16% K⁻¹ and peak TCR temperature of 289.42 K, demonstrating that suitable candidates can be obtained for infrared detection technology.
... Hwang et al. indicated that lower values of average cationic radius of rare-earth site would suppress the double exchange and then increase the MR ratio [31]. And this phenomenon was found in La 2/3 Sr 1/3 MnO 3 [32] [37]; Anand et al. reported the magnetotransport and thermal properties of Nd and Smdoped LCMO bulk polycrystalline samples [38]. But Nd doping effect on the electrical and magnetic properties LCMO film has not been investigated in detail. ...
Nd-doped La0.67Ca0.33MnO3 (La0.67-xNdxCa0.33MnO3) gel films were fabricated on Si (00l) and LaAlO3 (00l) substrates using sol–gel method and acetylacetone as chelating agent. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and X-ray photoelectron (XPS) were used to characterize the structure, composition, and morphology of the films. The electrical transport properties were measured on a physical property measurement system (PPMS) under a relatively low external magnetic field (1 T). Results show that the La0.67-xNdxCa0.33MnO3 films present to be randomly oriented on Si (00l) substrate, but grow epitaxially on LaAlO3 (00l) substrate. Both the magnetoresistance effect and saturation magnetization of the La0.67-xNdxCa0.33MnO3 films are significantly enhanced by Nd doping, although the metal–insulator transition temperature (TIM) decreases. The electrical transport properties of films deposited on Si (00l) and LaAlO3 (00l) substrate are almost same, viz. increases firstly and then decreases with the increase of Nd doping content. When the Nd doping content x = 0.35, the magnetoresistance change rate reaches the maximum value, which is 24.8% and 86.9% of that of the film deposited on Si (00l) and LaAlO3 (00l) substrate, respectively. However, the saturation magnetization reaches the highest level at the Nd content x = 0.15, viz. 520 and 1058 emu/cm³ at 50 K for the films deposited on Si (00 l) and LaAlO3 (00 l) substrate.
... In fact, we observe a weakly value for ZnNb1, 5 and 10%, and then, it increases with ZnNb15 and 20%. This fact may be due to the structural distortion [40], and thus, the increase on Nb 2 O 5 percentage enhances the distortion in the NbO 6 octahedron, observation proved also by FTIR measurement. Subsequently, the resistivity and the magnetoresistance increase. ...
In this work, (1-x) ZnO/xNb2O5 mixture with (x = 0.01, 0.05, 0.1, 0.15 and 0.2) is used to synthesize composites by means of the solid-state method. The X-ray analysis affirms the formation of ZnO/ZnNb2O6 binary composite for x = 0.01, while ZnO/ZnNb2O6/Nb2O5 ternary composite was formed from x = 0.05. The morphological distribution confirms that the average grain size increases with the increase of Nb2O5 percent. Moreover, the dielectric and electric properties of the composites are investigated using impedance spectroscopy and van der Pauw method. In fact, using the theoretical adjustment of the curve the material is modeled with an equivalent electric circuit including two parallel combinations of resistance and fractal capacitance, related to grains and grain boundary contributions. This study demonstrates the enhancement of the grain boundary contributions in the composites compared to ZnO, and high resistive and capacitive behavior. Moreover, the composites have lower loss factor than ZnO. Furthermore, it can be seen that the dielectric properties of the composites are changed as a function of Nb2O5 percentage. The 10% composite presents low resistance, high charge carrier’s concentration and high mobility, high permittivity and important capacitive behavior. For higher percent (≥ 15 mol%), the composites become more resistive with low mobility and low charge carrier’s concentration, high permittivity and a capacitive behavior. The enhancement in the dielectric properties with increasing Nb2O5 concentration suggests that these composites are useful for various dielectric device applications. In addition, the magnetic analysis demonstrates that from x = 0.1 the composite exhibits ferromagnetic behavior at room temperature.
... To meet the application requirements in the fields of magnetic sensors, spintronic devices, magnetocaloric refrigeration, magnetic resonance imaging, and drug delivery, the physical properties of LCMO NPs are urgently to be improved. It has been reported that the substitution of La 3+ ions by smaller and magnetic heavy rare earth elements is an effective route to achieve the above aims [10][11][12][13][14]. In the previous works [15,16], we have reported the synthesis, structural characterization, magnetic and optical properties of Ln-doped LCMO (Ln=La, Pr, Nd and Sm) NPs. ...
In this work, (La 0.6 Ln 0.4 ) 0.67 Ca 0.33 MnO 3 (Ln = La, Pr, Nd and Sm) nanoparticles (NPs) synthesized by sol-gel process were investigated by electron spin resonance (ESR) in the temperature range 100–330 K. At the high temperature the ESR signals of La 0.67 Ca 0.33 MnO 3 (LCMO) NPs only consist of a single peak with Landé g factor of 2.0. This signal is contributed from the paramagnetic (PM) Mn ions in the LCMO NPs. With decreasing the temperature the PM resonance line is split into two resonance lines, one is ferromagnetic (FM) resonance line shifting towards low field while the other is antiferromagnetic (AFM) resonance line moving to a high field. The resonance peak-to-peak spectra linewidth, increases monotonically with decreasing the temperature owing to the strong double exchange interactions below the Curie temperature ( T C ). Resonance field is almost temperature independent in the PM phase whereas it drops fast at temperature below T C . Consequently, the Landé g factor in the PM region is very close to 2.0 whereas in the range of 2.17–2.47 under FM state due to the strong FM interactions. For the Pr (Nd)-doped LCMO NPs below T C , their g values are in the range of 2.04–2.18 due to the substantial reduction of the FM interactions caused by the Pr (Nd)-doping at La-site. The g values of the Sm-doped LCMO NPs exhibit a slight fluctuation around 1.88 (but smaller than 2.0) within the measured temperature due to the existence of weak magnetic interactions under the PM states.
... Typically, the higher is the TCR of the perovskite, the better is its infrared detection sensitivity. Thus, many studies aimed to achieve as high as possible TCR values of the target perovskites [23][24][25][26]. Another important fact is that the Tp or Tk value of the perovskite chosen for electronic applications should cover a room-temperature range. ...
During the exploration on the temperature coefficient of resistance (TCR) of A-site cation-doped perovskites, divalent cation-doped material systems have received increasing attention; however, the TCR performance of monovalent cation-doped perovskites has been less studied. In order to investigate the effect of monovalent Na cation doping on the TCR of La1-xNaxMnO3 (LNMO, x = 0.1, 0.2, 0.3, 0.4, and 0.5) and obtain LNMO materials possessing high TCR values at room temperature, the LNMO perovskite ceramics were synthesized by the Pechini sol–gel method. The effect of sodium cation doping on their structural and electrical properties was investigated by various characterization methods. An increase in Na content affected the grain size and Mn⁴⁺ ion concentration in the LNMO ceramics. Furthermore, increasing quantity of Na significantly increased the TCR from 5.89 % K⁻¹ at x = 0.1–8.56% K⁻¹ at x = 0.4. For a Na-doping level x = 0.4, the peak TCR temperature (Tk) at room temperature reached 299.42 K. Among the feasible reasons that could improve the above electrical parameters are the weakened grain boundary scattering, the increase in A-site vacancy, the enhanced double-exchange effects, and the generation of Jahn–Teller distortions. According to the results of this study, the obtained LNMO ceramics seem to be promising for the application in uncooled infrared bolometer technology.
