【摘要】 将用溶胶-凝胶法制备的La0.67Sr0.33MnO3(LSMO)微粉与(Nb2O5)x/2粉在1100℃下混合烧结,形成了具有钙钛矿结构的锰氧化物与LaNbO4的复合体系,x是掺入的Nb5+离子与母体材料的摩尔比。在x=0.07的样品中得到最大电阻率为23.74Ω.cm,比LSMO高三个数量级。Nb5+离子的掺杂使样品的低场磁电阻(LFMR)和高场磁电阻(HFMR)效应都有所增强。77 K下,0.1 T和1 T磁场下在x=0.07样品中分别得到24%和33.8%的磁电阻效应,是LSMO样品的2倍和1.7倍。室温下x=0.05样品的磁电阻最大,为9%。其中,LFMR来源于颗粒晶界处电子的自旋相关隧穿及散射作用,而HFMR来源于表面层的自旋非共线结构。更多还原

【Abstract】 The composites of pervoskite structure manganites and LaNbO4 were prepared by calcining(Nb2O5)2/x and La0.67Sr0.33MnO3(LSMO) powder at 1100℃,where x is the molar ratio of the Nb ions to LSMO.The LSMO powder was synthesi{ed by the sol-gel method.There is a maximum resistivity ρ(23.74 Ω·cm) for the sample with x = 0.07,which is higher than that for LSMO by three orders of magnitude.The MR ratios at 77 K with H = 1 T and H = 0.1 T are 33.8 % and 24 % for the x = 0.07 doped sample,respectively.A MR effect up to 9 % was also found for the sample with x = 0.05 at room temperature,which is 2.2 times as large as that for LSMO(4.1 %).The spin dependent tunneling and scattering at the grain boundaries are responsible for the low field magnetoresistance(LFMR) while the high field magnetoresistance(HFMR) originates from the spin dependent transport related to noncolinear spin structure at the interfaces.更多还原