半掺杂Sm_(0.5)Ca_(0.5)MnO_3体系的电荷有序和再入型自旋玻璃行为

Charge order phase and reentrant spin-glass behavior in half doped Sm_(0.5)Ca_(0.5)MnO_3 manganite

研究了半掺杂锰氧化物Sm0·5Ca0·5MnO3体系的结构、输运和磁特性,结果表明,在半掺杂情况下,该体系呈现O′类正交结构,表明体系存在典型的Jahn-Teller效应畸变;输运结果在整个测量温区均呈现半导体导电行为,没有出现金属-绝缘体(M-I)转变和CMR效应;电荷有序转变发生在T=270K左右,反铁磁转变温度出现在200K附近,且表现出典型的再入型自旋玻璃(spin-glass)行为,自旋玻璃转变温度TSG在41K附近,同时,观察到了存在于该体系中负的磁化异常,表明半掺杂的Sm0·5Ca0·5MnO3基态存在有多种复杂而丰富的磁相互作用之间竞争机制,其研究将为强关联锰氧化物体系物理机理的理解提供丰富的实验资料.

The structure, transport and magnetic properties of half doped Sm0.5Ca0.5MnO3 manganite has been systamatically studied. The results show that Sm0.5Ca0.5MnO3 compound has the O＇ orthorhombic structure and shows typical Jahn-Teller distortion. Throughout the temperature range used, the electric transport shows semiconducting behavior and there are no I-M transition and CMR effect. Meanwhile, it is found that the charge-order and antiferromagnetic transition temperatures of the system are around 270K and 200K, respectively, whereas at lower temperature there appears a typical spin-glass state around 41K with reentrant behavior. The negative magnetization is also observed in this compound. All these phenomena indicate that for the ground state of Sm0.5Ca0.5MnO3, there exists the competition mechanism of several complex magnetic interactions. Present study may provide abundant experimental information for understanding the mechanism of the strongly electron correlated system.