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A series of the samples La_(1-x)(Sr_(1-y)Na_y)_xMnO_3(y=0.0,0.2,0.4,0.6,0.8,1.0) were prepared by the solid-state reaction method.Magnetoresistance enhancement and temperature stability of magnetoresistance in the system La_(1-x)(Sr_(1-y)Na_y)_xMnO_3 with unchanged Mn~(3+)/Mn~(4+) ratio through the doping of both monovalent and divalent elements at A site were studied through the measurements of X-ray diffraction(XRD) patterns,resistivity-temperature(ρ-T) curves and magnetoresistance-temperature(MR-T) curves.The results indicate that with the increase of Na doping amount,the peak value of MR increases,and it increases from 12.4% for y=0.2 to 50.6% for y=1.0 in the magnetic field B=0.8 T;ρ-T curves exhibit the double-peak phenomenon,which comes from the competition between the resistivity of surface phase and that of body phase;for the sample of y=0.8,MR increases slowly from 8.3% to 9.4% in the temperature range from 259 to 179 K,and MR is so stable in such a wide temperature range,which provides reference for the research on the temperature stability of MR.
A series of the samples La_ (1-x) (Sr_ (1-y) Na_y) _xMnO_3 (y = 0.0,0.2,0.4,0.6,0.8,1.0) were prepared by the solid-state reaction method. Magnetoresistance enhancement and temperature stability of magnetoresistance in the system La_ (1-x) (Sr_ (1-y) Na_y) _xMnO_3 with unchanged Mn ~ (3 +) / Mn ~ (4+) ratio through the doping of both monovalent and divalent elements at A site were studied through the measurements of X-ray diffraction (XRD) patterns, resistivity-temperature (ρ-T) curves and magnetoresistance-temperature (MR-T) curves.The results that that with the increase of Na doping amount, the peak value for MR increases, and it increases from 12.4% for y = 0.2 to 50.6% for y = 1.0 in the magnetic field B = 0.8 T; ρ-T curves exhibit the double-peak phenomenon, which comes from the competition between the resistivity of for the sample of y = 0.8, MR increase slowly from 8.3% to 9.4% in the temperature range from 259 to 179 K, and MR is so stable in such a wide temperature range, w hich provides reference for the research on the temperature stability of MR.