多铁材料SmFe1-xCrxO3陶瓷的介电特性及磁相变的研究

Study on structure, dielectric properties and magnetic phase transition of multiferroic SmFe1-xCrxO3 ceramics

采用溶胶-凝胶法制备SmFe1-xCrxO3(x=0~0.3)样品,研究Cr^3+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,Cr^3+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(εr)随着掺杂量(x)的增加逐渐减小,介电损耗(tanδ)随着Cr^3+的增加而增大,介电常数(εr)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SmFe1-xCrxO3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Cr^3+的掺杂而消失且磁性也有所减弱,其自旋重组相变温度(TSR)和反铁磁相变温度(TN)随着Cr^3+的增加由原来的462,687K降低到428和536K。这主要是Cr^3+掺杂使SmFeO3晶格发生畸变,形成Fe^3+-O^2--Cr^3+磁交换作用,破坏了原有Fe^3+-O^2--Fe^3+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TSR和TN的降低,进一步探讨了Cr^3+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。

Sm1-xCrxFeO3 (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.Cr^3+ 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 (εr) and dielectric loss (tanδ) of SmFeO3 gradually decreased with the increase of Cr^3+.The variation ofεr 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 SmFe1-xCrxO3 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 ofxand the magnetic properties also gradually weakened.In a M-T relationship with an applied magnetic field of 79 600 A/m,TSR and TN decreased from 462 and 687K to 428 and 536K with increasingx,respectively.This was mainly due to Cr^3+ doping to distort the lattice of SmFeO3,forming Fe^3+-O^2--Cr^3+ exchange,destroying the antiferromagnetic ordering of Fe^3+-O^2--Fe^3+ 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 TSR and TN decreased.