Dy的高掺杂对La_(0.7)Sr_(0.3)MnO_3体系磁电性质的影响

Influence of heavy-doping with Dy on the magnetic and electrical properties in La_(0.7)Sr_(0.3)MnO_3

通过实验研究了La0 7-xDyxSr0 3MnO3(x =0 0 0 ,0 30 ,0 4 0 ,0 5 0 ,0 6 0 ,0 70 )体系的M_T曲线 ,M_H曲线 ,ρ_T曲线和MR_T曲线 .实验结果表明 :随着Dy掺杂的增加 ,体系从长程铁磁有序向自旋团簇玻璃态、反铁磁及亚铁磁状态转变 .x =0 30样品的M_T曲线上在TN 附近出现磁化强度尖峰 ,x =0 4 0时尖峰消失 .对x =0 5 0样品 ,ZFC的M_T曲线随温度增加出现一个谷 ,随后在TN 处出现峰 ;而FC的M_T曲线在低温下呈现负磁矩 .对x =0 6 0和0 70样品 ,不论FC还是ZFC的M_T曲线都类似于x =0 5 0的ZFC的M_T曲线 .高掺杂时的输运性质在其磁背景下发生异常 .这些奇异现象用N el的双格子模型并联合M_H回滞曲线给予很好地解释 .

The M-T curves, M-H curves, rho-T curves and MR-T curves of La0.7-x DyxSr(0.3)MnO(3) (x = 0.00,0.30,0.40,0.50,0.60 and 0.70) are studied. Experimental results indicate that with increasing doping concentration of Dy, the system changes from long-range ferromagnetic order to cluster-spin glass state, then to antiferromagnetic state and to subferromagnetic state. For x = 0.3, there appears a peak on the M-T curve near T-N however, it disappears at x = 0.4. For x = 0.5, and zero field cooling (ZFC) the curve shows a valley, and then a peak at T-N; after the 0.01 T field cooling process, the initial value of M is negative at low temperatures. For x = 0.60 and 0.70, their ZFC and FC M-T curves are both similar to the ZFC one of x = 0.50, and the transport properties at heavy doping become abnormal under a magnetic background. The peculiar phenomena shown above can be interpreted in terms of the Neel's double-lattice model combined with the results of M-H hysteresis at the characteristic temperatures.