Ru掺杂BaFe2As2体系Ba(Fe1-xRux)2As2的面内电输运性质演化研究

Evolution of In-Plane Electrical Transport Properties of Ru Doped BaFe2As2 System Ba(Fe1-xRux)2As2

纵向磁阻能够反映铁砷化合物中载流子和自旋自由度间相互作用,为利用其对等价掺杂铁砷化合物的输运性质和自旋磁涨落进行研究,采用高温助熔剂法制备了高质量的Ba(Fe1-xRux)2As2单晶样品,测量了其中超导样品的ab面面内纵向磁阻。发现外场H作用下电阻值降低且磁阻大小随H2线性增大,分析表明负的纵向磁阻源于磁场对体系自旋涨落的压制效应;随着Ru掺杂量x增加,纵向磁阻系数曲线逐步下移,说明欠掺杂样品中自旋涨落较为剧烈,曲线下移反映了掺杂对体系内反铁磁自旋涨落的压制过程;应用二维反铁磁金属巡游电子模型对纵向磁阻的定性分析发现:随Ru掺杂量增加,模式耦合系数在最佳掺杂量子临界点处形式发生改变,说明伴随体系长程反铁磁序完全被压制,最佳掺杂和过掺杂样品内载流子与自旋涨落的作用方式产生了变化。

Single crystals of Ba(Fe1-xRux)2 As2 were grown out of self flux using conventional high-temperature solution growth techniques,and a T-x(0≤x≤0.425)phase diagram was summarized using the data derivated from temperature dependent resistances.The longitudinal in-plane magnetoresistance(LMR)has been measured on different superconducting Ba(Fe1-x、Rux)2 As2 single crystals.For all the samples,a negative LMR is found in the paramagnetic state whose magnitude increases as and the suppression of spin fluctuations by the applied magnetic field could account for this minus LMR.The temperature dependent LMR coefficient curves are found to shift down systematically with the increasing doping level x,which shows the detailed procedure of suppression and the existence of drastic magnetic fluctuation in the underdoped samples.The analysis of its T dependence in an 2 D itinerant nearly antiferromagnetic metal model evidences that the mode coupling coefficientα(T)exhibits a qualitative change of T variation with increasing Ru content.The latter occurs exactly at quantum critical point(QCP)where the antiferromagnetic ground state is completely suppressed,indicating the change of interaction between the conduction electrons and the fluctuating magnetic moments.LMR provides a powerful tool for studying the coupling effect between the charge carriers and the spin degrees of freedom in such iron pnictide materials.