中文摘要：

通过磁化强度和电阻的测量对多晶样品（La1-xGdx）0.5Sr0.5MnO3（x=0,0.1,0.2,0.3,0.4）的电磁特性进行了系统的实验研究。当x≤0.2时,样品显示出铁磁金属态（FMM）到顺磁绝缘态（PM I）的转变;当0.3≤x≤0.4时,金属-绝缘体转变温度Tp消失,样品显示出反铁磁绝缘态（AFM I）到顺磁绝缘态（PM I）的转变。同时随着x的增加所有样品的居里温度Tc和金属-绝缘体转变温度Tp都降低,并且在居里温度附近观测到了磁电阻效应。

英文摘要：

Electronic and magnetic properties of polycrystalline samples（La1-xGdx）0.5Sr0.5MnO3（x=0,0.1,0.2,0.3,0.4）were systematically studied by the measurements of magnetization and resistance.When x≤0.2,samples exhibit a transition from a ferromagnetic metal state（FMM） to a paramagnetic insulator state（PMI）;The metal-insulator transition temperature is disappear,the antiferromagnetic insulator（AFMI）-paramagnetic insulator（PMI） transition shows up in the compositions for 0.3≤x≤0.4.Meanwhile,for all samples,both the curies temperature Tc and the metal-insulator transition temperature decrease with increasing Gd content,and MR effect near Tc can be observed.