V替代Mn对La_(0.45)Ca_(0.55)MnO_3电荷有序相及自旋玻璃态的影响

用固相反应法制备了La0.45Ca0.55Mn1-xVxO3(x=0.00,0.10)多晶样品.通过X射线衍射谱、质量磁化强度-温度曲线、电子自旋共振谱,研究了V5+替代Mn3+/Mn4+对La0.45Ca0.55MnO3电荷有序相和自旋玻璃态的影响.实验结果表明,当x=0.10时,不仅母体的电荷有序相基本破坏,而且母体在40K左右出现的自旋玻璃态也被融化.电荷有序相被破坏的主要原因是用V5+替代Mn3+/Mn4+后,增加了Mn3+与Mn4+的比例,使铁磁双交换作用优于反铁磁超交换作用;自旋玻璃态的融化是由于V替代Mn后破坏了反铁磁背景下有少量铁磁成分的自旋玻璃态的形成条件.

Effects of V substitution for Mn on charge ordering and spin-glass state in La0.45Ca0.55MnO3 sample

The polycrystalline samples of La_0.45Ca_0.55Mn_1-xV_xO₃(x=0.00, 0.10) have been prepared by the solid-phase reaction. Efects of V⁵⁺ substitution for Mn³⁺/Mn⁴⁺ on charge ordering and spin-glass state are studied by X-ray diffraction spectrum, temperature dependence of magnetization, and electron spin resonance spectra. The results indicate that charge ordering of the original system is almost destroyed, and spin-glass state at about 40 K is melted by 10% of V substitution for Mn. The charge ordering phase is destroyed mainly because of V⁵⁺ ions substitution for Mn³⁺/Mn⁴⁺, which increases the ratio of Mn³⁺ to Mn⁴⁺ and so causes ferromagnetic double-exchange to be superior to antiferromagnetic super-exchange. In addition, the spin-glass state is melted because V substitution for Mn destroys the formation condition of spin-glass state that a small quantity of ferromagnetic components exist under the antiferromagnetic backgrornd.