جستجوی مقالات مرتبط با کلیدواژه « tunelling » در نشریات گروه « فیزیک »

In this research single phaseLa0.7(Sr 1-xBax)0.3MnO3(x =0, 0.1 , 0.2 , 0.3) nanomanganite with crystalline size of 18-28 nm have been prepared by sol gel method. The structural properties have been studied using X-ray diffraction spectra with its Rietveld analysis and scaning electron microscope images. The magnetic and elctrical properties have been investigated by measuring the ac magnetic susceptibility and resistivity in the presence of magnetic fields in the range of 0-20 kOe. The obtained results from ac magnetic susceptibility show that the Curie temperture of the samples are above room temperture. The results of resistivity show that the metal-insulator phase transition temperture of La0.7 Sr0.3 MnO3 and La0.7 (Sr0.3 Ba0.2) MnO3 compounds are below room temperture. The resistivity of the samples strongly decreases and their magnetoresistance almost linearly increases by incrasing the applied magnetic field at different tempertures. The value of magnetoresistance for La0.7 (Sr0.3 Ba0.2) MnO3 Ecompound is 10 % and 14 % at 275 K and 200 K, and for La0.7 Sr0.3 MnO3 Ecompound is 13 % and 27 % at 275 K and 100 K, respectively which are suitable for magnetic field sensing applications. The magneto-transport properties of La0.7 (Sr1-x Bax) MnO3 nanomanganite are described in terms of spin dependent scattering of charge carriers from grain boundaries and their spin dependent tunneling between grains.