【摘要】 采用溶胶-凝胶法制备SmFe_1-xCr_xO₃（x=0～0.3）样品,研究Cr³⁺掺杂对SmFeO₃的晶体结构、介电特性及磁相变温度的影响。研究表明,所有样品的主衍射峰与SmFeO₃标准图谱相吻合且具有良好的晶体结构,Cr³⁺掺杂使其晶胞体积收缩,导致主衍射峰向衍射角（θ）较大的方向移动。SmFeO₃的介电常数（ε_r）随着掺杂量（x）的增加逐渐减小,介电损耗（tanδ）随着Cr³⁺的增加而增大,介电常数（ε_r）随频率（f）和掺杂量（x）的增加而逐渐减小的原因是由IBLC微观机制和偶极子取向极化机制两者共同作用的结果,其介电损耗主要是电导电流产生的损耗起主导作用,并发现SmFe_1-xCr_xO₃的介电损耗峰随掺杂量的增加向高频方向迁移。SmFeO₃的蜂腰状M-H随着Cr³⁺的掺杂而消失且磁性也有所减弱,其自旋重组相变温度(T_SR)和反铁磁相变温度（T_N）随着Cr³⁺的增加由原来的462,687 K降低到428和536 K。这主要是Cr³⁺掺杂使SmFeO₃晶格发生畸变,形成Fe³⁺-O^2--Cr³⁺磁交换作用,破坏了原有Fe³⁺-O^2--Fe³⁺反铁磁有序排列,降低了其G型反铁磁结构的稳定性,在宏观上表现为其铁磁性的减弱和磁相变温度T_SR和T_N的降低,进一步探讨了Cr³⁺掺杂对SFO的介电性及铁磁性影响的微观机理,使其在自旋电子器件、磁制冷领域及磁性开关器件等方面的应用成为可能。更多还原

【Abstract】 Sm_1-xCr_xFeO₃（x=0-0.3） ceramics were prepared by the sol-gel method. Effects of Cr doping on the crystal structure, dielectric properties and high temperature magnetic phase transitions of SFO were investigated. XRD pattern analysis shows that the main diffraction peaks of all the samples were agree with the standard SFO spectra and had a fine crystal structure. Cr³⁺ doping resulted in the cell volume to shrink, causing its main diffraction peak to move in the direction of the larger diffraction angle（θ）. The dielectric constant（ε_r） and dielectric loss（tanδ） of SmFeO₃ gradually decreased with the increase of Cr³⁺. The variation of ε_r with f and x was mainly the result of both the IBLC microscopic mechanism and the dipole oriented polarization mechanism, and the dielectric loss（tanδ） was mainly caused by the electric conduction current. And found that the dielectric loss peak of SmFe_1-xCr_xO₃ migrated to the high frequency direction with the increase of doping amount. The M-H of SmFeO₃ at room temperature showed a butterfly-shaped hysteresis loop. The butterfly-shaped hysteresis loop disappeared with the increase of x and the magnetic properties also gradually weakened. In a M-T relationship with an applied magnetic field of 79 600 A/m, T_SR and T_N decreased from 462 and 687 K to 428 and 536 K with increasing x, respectively. This was mainly due to Cr³⁺ doping to distort the lattice of SmFeO₃, forming Fe³⁺-O^2--Cr³⁺ exchange, destroying the antiferromagnetic ordering of Fe³⁺-O^2--Fe³⁺ and leading to the weakening of the stability of the G-type antiferromagnetic structure of SFO. Macroscopically, the ferromagnetism of SFO decreased and the magnetic transition temperatures T_SR and T_N decreased.更多还原