Current and near-term microelectronic applications are placing greater and greater demands on functional materials with novel electronic and magnetic properties. Multiferroic materials are an example of a functional material with simultaneous ferroelectric and magnetic properties in the same phase. Combining ferroelectricity and magnetism in a single-phase compound would obviously be of tremendous interest not only to practical applications but also to fundamental physics. The intrinsic ability to couple the electrical polarization to the magnetization allows an additional degree of freedom in the design of conventional devices.
$x(Bi_{0.1}La_{0.9}FeO_3)-(1-x)A(Fe_{1/2}Nb_{1/2)O_3$ (A=Sr, Pb) system were prepared by solid state reaction method. (BLFO-SFNO, BLFO-PFNO) We expect developing of spin alignment through the B-site cation ordering and construction of stable ferroelectric phase using complex double perovskite system.
It was observed that distorted rhombohedral-like structure of BLFO was transformed to pseudo-cubic structure of SFNO as Sr content increased. However, BLFO-PFNO system was transformed to non-symmetry structure. BLFO-SFNO system was detected impurity phase. BLFO-PFNO was single phase and X-ray diffraction (XRD) and energy disperse spectroscopy (EDS) confirmed their single-phase characteristic, phase purity, and structural variation. BLFO-PFNO was represented dielectric behavior at room temperature and Weak ferromagnetism was observed. we observe large Pr value and low leakage current at rich PFNO composition. Thus leakage current and polarization tend to be affected by Pb composition. BLFO-PFNO was expected to be below room temperature but pure and rich PFNO composition represented weak ferromagnetization at room temperature. As a result, we have developed the multiferroic properties of single-phase BLFO-PFNO materials.
다강체는 강유전, 강자성, 강탄성이 한 물질 내에서 동시에 구현되는 물질이다. 기존의 소자들이 하나의 특성 제어만을 통하여 응용되었다면, 단일 상 내에서 강유전 특성과 강자성 특성의 고유한 결합 원리를 내재한 다강체 물질은 증가된 자유도의 “읽기/쓰기”를 가능케 함으로서 새로운 개념의 소자 개발에 있어 혁명적 가능성을 제시하고 있다. 본 연구는 $x(Bi_{0.1}La_{0.9}FeO_3})-(1-x)A(Fe_{1/2}Nb_{1/2})O_3$ (A=Sr, Pb) 의 고상고용 합성법을 이용하여 물질 변화에 따른 자성특성 및 유전특성의 변화를 살펴보았다. BLFO-SFNO 조성에서 Sr의 함량이 많아짐에 따라 구조적 대칭성이 증가하면서 유전특성이 약화되고 Fe-rich한 2차상의 생성으로 인하여 자성특성이 증가됨을 확인하였다. 또한 BLFO-SFNO조성에서는 유전손실 및 누선전류가 크게 측정됨을 관찰할 수 있었다. BLFO-PFNO 조성에서는 Pb의 함량이 많아짐에 따라 구조적 비대칭성이 증가하면서 유전특성이 강화되고, 또한 구조적 변화에 따른 자성특성의 강화 또한 확인할 수 있었으며 유전손실 및 누설전류가 BLFO-SFNO조성에 비해서 적게 측정되었다. 따라서 두 가지 조성의 실험을 통하여 단일상의 BLFO-PFNO 고상고용체의 합성을 통해 다강체 특성향상을 확인하였다.
