اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدImpact of silver addition on room temperature magneto-resistance in La0.7Ba0.3MnO3 (LBMO): Agx (x = 0.0, 0.1, 0.2, 0.3, 0.4)
155
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
La0.7Ba0.3MnO3 (LBMO):Agx (x = 0.0, 0.1, 0.2, 0.3, and 0.4) composites are synthesized by solid-state reaction route, the final sintering temperatures are varied from 1300 (LBMO1300Ag) to 1400 0C (LBMO1400Ag), and their physical properties are compared as a function of temperature and Ag content. All samples are crystallized in single phase accompanied by some distortion in main structural phase peaks at higher angles with increase in silver content. Though the lattice parameters (a, c) decrease, the b increases slightly with an increase in Ag content. The scanning electron micrographs (SEM) showed better grains morphology in terms of size and diffusion of grain boundaries with an increase in Ag content. In both LBMO1300Ag and LBMO1400Ag series the metal insulator transition (TMI) and accompanied paramagnetic-ferromagnetic transition (TC) temperatures are decreased with increase in Ag content. The sharpness of MI transition, defined by temperature coefficient of resistance (TCR), is improved for Ag added samples. At a particular content of Ag(0.3), the TMI and TC are tuned to 300K and maximum magneto-resistance at 7Tesla applied field (MR7T) of up to 55% is achieved at this temperature, which is more than double to that as observed for pure samples of the both 1300 and 1400 0C series at same temperature. The MR7T is further increased to above 60% for LBMOAg(0.4) samples, but is at 270K. The MR7T is measured at varying temperatures of 5, 100, 200, 300, and 400K in varying fields from +/- 7 Tesla, which exhibits U and V type shapes. Summarily, the addition of Ag in LBMO improves significantly the morphology of the grains and results in better physical properties of the parent manganite system.
قيم البحث
اقرأ أيضاً
Raman spectra of polycrystalline NdFeAsO1-xFx (x=0.0, 0.1, 0.2) compound have been systematically investigated as functions of temperature and fluorine concentration. Scanning electron microscopic and Raman microscopic characterization demonstrates t
hat the polycrystalline samples mainly contain two phases, i.e. superconductor NdFeAsO1-xFx compound and a MnP-type FeAs phase, with dissimilar characteristic Raman bands. It was found that fluorine doping leads to structure disorder in the insulator Nd-O layers and high temperature coefficient of Fe-As vibrational mode.
The magnetic and magnetocaloric properties of polycrystalline La0.70(Ca0.30-xSrx)MnO3:Ag 10% manganite have been investigated. All the compositions are crystallized in single phase orthorhombic Pbnm space group. Both, the Insulator-Metal transition t
emperature (TIM) and Curie temperature (Tc) are observed at 298 K for x = 0.10 composition. Though both TIM and Tc are nearly unchanged with Ag addition, the MR is slightly improved. The MR at 300 K is found to be as large as 31% with magnetic field change of 1Tesla, whereas it reaches up to 49% at magnetic field of 3Tesla for La0.70Ca0.20Sr0.10MnO3:Ag0.10 sample. The maximum entropy change (DeltaSMmax) is 7.6 J.Kg-1.K-1 upon the magnetic field change of 5Tesla, near its Tc (300.5 K). The La0.70Ca0.20Sr0.10MnO3:Ag0.10 sample having good MR (31%1Tesla, 49%3Tesla) and reasonable change in magnetic entropy (7.6 J.Kg-1.K-1, 5 Tesla) at 300 K can be a potential magnetic refrigerant material at ambient temperatures.
The gigantic decrease of resistance by an applied magnetic field, which is often referred to as colossal magnetoresistance (CMR), has been an attracting phenomenon in strongly correlated electron systems. The discovery of CMR in manganese oxide compo
unds has developed the science of strong coupling among charge, orbital, and spin degrees of freedom. CMR is also attracting scientists from the viewpoint of possible applications to sensors, memories, and so on. However, no application using CMR effect has been achieved so far, partly because the CMR materials which satisfy all of the required conditions for the application, namely, high operating temperature, low operating magnetic field, and sharp resistive change, have not been discovered. Here we report a resistance change of more than two-orders of magnitude at a magnetic field lower than 2 T near 300 K in an A-site ordered NdBaMn_2_O_6_ crystal. When temperature and a magnetic field sweep from insulating (metallic) phase to metallic (insulating) phase, the insulating (metallic) conduction changes to the metallic (insulating) conduction within 1 K and 0.5 T, respectively. The CMR is ascribed to the melting of the charge ordering. The entropy change which is estimated from the B-T phase diagram is smaller than what is expected for the charge and orbital ordering. The suppression of the entropy change is attributable to the loss of the short range ferromagnetic fluctuation of Mn spin moments, which an important key of the high temperature and low magnetic field CMR effect.
We report high field (up to 13 Tesla) magneto transport R(T)H] of YBa2Cu3O7 (YBCO):Agx (x= 0.0, 0.1 and 0.2) composites. The transport properties are significantly improved by Ag doping on the insulating grain boundaries of YBCO. Pure and Ag diffused
YBCO superconducting samples are synthesized through solid state reaction route. Both pure and Ag doped YBCO are superconducting at below 90K. Though, the Tc (R=0) of YBCO:Ag samples under applied field of 13 Tesla is around 65K, the same is 45K for pure YBCO under same applied field. The upper critical field [Hc2(0)], being estimated from R(T)H is around 70Tesla for pristine sample, and is above 190Tesla for Ag doped samples. The boarding of the resistive transition under applied magnetic field is comparatively less and nearly single step for Ag doped samples, while the same is clearly two step and relatively much larger for the pristine YBCO. The resistive broadening is explained on the basis of changed inter-granular coupling and thermally activated flux flow (TAFF). The TAFF activation energy (U0) is found to be linear with applied magnetic field for all the samples, but with nearly an order of magnitude less value for the Ag doped samples. Summarily, it is shown that inclusion of Ag significantly improves the superconducting performance of YBCO:Ag composites, in particular under applied field.
We have measured magnetic susceptibility and resistivity of Sr$_{1-x}$Y$_x$CoO$_{3-delta}$ ($x=$ 0.1, 0.15, 0.2, 0.215, 0.225, 0.25, 0.3, and 0.4), and have found that Sr$_{1-x}$Y$_x$CoO$_{3-delta}$ is a room temperature ferromagnet with a Curie temp
erature of 335 K in a narrow compositional range of 0.2 $leq xleq$ 0.25. This is the highest transition temperature among perovskite Co oxides. The saturation magnetization for $x=$ 0.225 is 0.25 $mu_B$/Co at 10 K, which implies that the observed ferromagnetism is a bulk effect. We attribute this ferromagnetism to a peculiar Sr/Y ordering.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
