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Polycrystalline samples of La12x(Sr12yAgy)x MnO3 (y = 0.0, 0.2, 0.4, 0.6, 1.0) were prepared by the solid-state reaction method. The temperature stability of magnetoresistance and magnetoresistance enhancement in La1-x(Sr1-yAgy)x MnO 3 system with both univalent and bivalent elements doped at A site and with unchanged value of Mn3+ /Mn4+ ratio were explored through the measurements of X-ray diffraction patterns, magnetiza-tion-temperature (M-T) curves, resistivity-temperature (q-T) curves and magnetoresistance-temperature (MR-T) curves. The results are as follows: there are two peaks in the q-T curves of the samples with Ag doping, one is caused by resistance change during the paramagnetism-ferromagnetism transition, and the other is from boundary-dependent scattering of conduction electrons on the boundaries of grains. The peak value of MR increases with increasing Ag doping content, and it increases from 8.2 % for y = 0.2 to 29.6 % for y = 1.0 under the magnetic field of B = 0.8 T; MR remains a constant of 12 % in the temperature range of 218-168 K for the sample with y = 1.0, and the temperature stability of MR is in favor of the practical application of MR.
The temperature stability of magnetoresistance and magnetoresistance enhancement in La1-x (Sr1-yAgy) x (Sr2yAgy) xMnO3 (y = 0.0, 0.2, 0.4, 0.6, 1.0) were prepared by the solid-state reaction method MnO 3 system with both univalent and bivalent elements doped at A site and with unchanged value of Mn3 + / Mn4 + ratio were explored through the measurements of X-ray diffraction patterns, magnetization-temperature (MT) curves, resistivity-temperature (qT) curves and magnetoresistance-temperature (MR-T) curves. The results are as follows: there are two peaks in the qT curves of the samples with Ag doping, one is caused by resistance change during the paramagnetism-ferromagnetism transition, and the other is from boundary-dependent scattering of conduction electrons on the boundaries of grains. The peak value of MR increases with increasing Ag doping content, and it increases from 8.2% for y = 0.2 to 29.6% for y = 1.0 under the magnetic field of B = 0.8 T; M R remains a constant of 12% in the temperature range of 218-168 K for the sample with y = 1.0, and the temperature stability of MR is in favor of the practical application of MR.