材料期刊网

本文报道了自助溶剂法制备的Li1-xNaxCu2O2（x=0,0.05,0.1,0.2）单晶沿c方向的磁化率随温度变化χ（T）的实验结果.随着Na掺杂量的增加,磁化率整体上移,高温区磁化率更加平缓;不同掺杂样品磁化率都在40K附近存在最大值,掺杂没有引起磁化率最大值对应的温度的变化,但引起了更低温下（T〈14K）磁化率的上翘,表明掺杂引入的无序使得自旋能隙被重新填充.高温区磁化率（T〉60K）拟合结果得到的铁磁相互作用J1、反铁磁相互作用J2均随掺杂量增加同步减小,阻挫变量α保持不变.X射线衍射结果表明Na均匀的的掺杂在母体中,晶胞参数a、b、c均随着掺杂量的增加而增大.磁相互作用的减小是与晶胞参数a、b、c的增加相关的.阻挫变量α的不变与磁化率最大值对应的温度以及体系最大概率磁转变温度的不变对应,从实验上证明了阻挫变量α是决定受挫体系性质的主要因素.

Li1-xNaxCu2O2（x=0,0.05,0.1,0.2）single crystals was prepared by self-flux method and the temperature dependent magnetic susceptibility χ（T） of all the crystals were measured along c axis.The magnetic susceptibility of the doped samples in high temperature region are more smooth than that of the undoped sample＇s.The doping of Na induced almost no change in the temperature（40K） corresponding to the maximum of magnetic susceptibility.But it caused the upturn of the magnetic susceptibility in low temperature region（T14K）,indicating the filling in the spin-gap.The magnetic susceptibility in high temperature region（T60K） of all the samples were fitted,it is found that the exchange coupling J1（ferromagnetic interaction） and J2（antiferromagnetic interaction） both decrease smoothly with the increase of doping level x,while the frustration parameter α is conformed unchanged.According to XRD,the lattice parameters a,b and c increase with the doping level x and no impurity phase was found in doped crystals.The decrease of exchange coupling is related to the increase of lattice parameters.The fact that the temperature corresponding to the maximum of magnetic susceptibility and temperature corresponding to the most possibile probability for the magnetic transition is unchanged,which is the result of that the frustration parameter α remains unchanged.It proved that α is the decisive factor for frustrated systems.