多铁性金属有机骨架材料铁弹性及力磁电耦合效应研究

Coupling effects of ferroelasticity, ferromagnetism and ferroelectricty are in the research frontier and among the hot topics in the fields of multiferroics. This work will focus on the investigation of elastic properties of multiferroic metal-organic frameworks (MOFs) associated with the ferroelastic, ferromagnetic and ferroelectrical transitions and the coupling effects of ferroelasticity, ferromagnetism and ferroelectricty, using Resonant Ultrasound Spectroscopy (RUS) with applied magnetic field of zero to 5 T, under high frequencies (0.1 – 1.5 MHz), high stress and strain, and Dynamic Mechanical Analysis (DMA) under low frequencies (0.1 – 100 Hz), low stress and strain, within the temperature range of 5 K to 300 K. Effects of magnetic field and frequency on the structural transition, magnetic transition and the disorder-order transition of hydrogen bonds will be studied, and the coupling effects of ferroelasticity, ferromagnetism and ferroelectricty will be investigated. Moreover, X-ray diffraction (XRD) will be used to study the structures within the temperature range of 150 K to 300 K and structure parameters will be determined. Based on Landau theory, the coupling effects of ferroelasticity, ferromagnetism and ferroelectricty will be studied. This work will enrich and broaden the investigations of coupling effects of ferroelasticity, ferromagnetism and ferroelectricty in different multiferroic materials. With the combined study of effects of magnetic field and frequency, and the investigation of elastic properties and structures, this work will provide important theoretic and experimental basis for the development of single-phase multiferroic materials with strong coupling effects of ferroelasticity, ferromagnetism and ferroelectricty as well as excellent mechanical properties.

力磁电耦合效应是多铁性材料领域的前沿和热点研究问题之一。本项目提出通过外加磁场的共振超声波谱法和动态机械分析法研究不同磁场强度（0 - 5 T）高频 (0.1 - 1.5 MHz) 低应力应变及低频（0.1 – 100 Hz）高应力应变条件下多铁性金属有机骨架材料在超低温至室温(5 - 300 K) 范围内弹性性能与铁弹、铁磁与铁电转变的内在关系及力磁电耦合效应。探究磁场强度和频率作用机制，揭示结构转变、磁性转变和氢键无序-有序转变规律及力磁电耦合强弱。另外，通过X射线衍射法研究低温至室温（150 - 300 K）范围内的相结构，利用晶格参数变化，基于朗道理论，分析力磁电耦合效应。通过本项目的研究可以丰富力磁电耦合研究体系与内容，结合磁场、频率的影响、弹性性能及结构研究，进一步揭示力磁电耦合效应的规律，为发展高温单相具有强力磁电耦合效应及优良机械性能的多铁性材料提供重要的理论和实验依据。

力磁电耦合效应是多铁性材料领域的前沿和热点研究问题之一。本项目通过扩散法和溶剂热法制备了金属有机骨架材料[(CH3)2NH2][M(HCOO)3] (M=Mg, Mn, Fe, Co, Ni, Zn)和[NH4][M(HCOO)3] (M=Mg, Mn, Co, Ni, Zn)。通过室温下的粉末X-射线衍射（XRD）确定了其结构，利用红外和拉曼光谱分析了官能团的振动,采用扫描电镜和透射电镜分析了形貌。利用差示扫描量热法分析了130-300 K范围内的热学性能，确定了铁电转变温度约为152-264 K。通过磁性性能测试系统研究了2-300 K范围内的磁性性能，确定了磁性转变温度约为8-38 K。利用变温XRD研究了5-300 K 范围内的结构变化。利用动态机械分析法研究了低频（0.5-10 Hz）高应力应变条件下130-300 K范围内储能模量、损耗模量和损耗因子随温度的变化，在铁电转变温度附近储能模量出现拐点，损耗模量和损耗因子出现峰值。在铁电转变温度附近出现明显的弹性异常和较大的能量衰减，表明铁弹性和铁电性之间具有明显的耦合效应。采用共振超声波谱法研究了高频（0.1-1.4 MHz）低应力应变条件下5-300 K范围内弹性性能和能量衰减随温度的变化，在磁性转变温度和铁电转变温度附近出现明显的弹性异常和较大的能量衰减，表明铁弹性与铁磁性及铁电性之间具有较强的耦合效应。通过本项目的研究丰富了力磁电耦合研究体系与内容，进一步揭示了力磁电耦合效应的规律，为发展高温单相具有强力磁电耦合效应及优良机械性能的多铁性材料提供了重要的理论和实验依据。