Brant Jacilynn A, dela Cruz Clarina, Yao Jinlei, Douvalis Alexios P, Bakas Thomas, Sorescu Monica, Aitken Jennifer A
Department of Chemistry and Biochemistry, Duquesne University , Pittsburgh, Pennsylvania 15282, United States.
Inorg Chem. 2014 Dec 1;53(23):12265-74. doi: 10.1021/ic5011693. Epub 2014 Nov 14.
Li2FeGeS4 (LIGS) and Li2FeSnS4 (LITS), which are among the first magnetic semiconductors with the wurtz-kesterite structure, exhibit antiferromagnetism with TN ≈ 6 and 4 K, respectively. Both compounds undergo a conventional metamagnetic transition that is accompanied by a hysteresis; a reversible spin-flop transition is dominant. On the basis of constant-wavelength neutron powder diffraction data, we propose that LIGS and LITS exhibit collinear magnetic structures that are commensurate and incommensurate with propagation vectors km = [1/2, 1/2, 1/2] and [0, 0, 0.546(1)], respectively. The two compounds exhibit similar magnetic phase diagrams, as the critical fields are temperature-dependent. The nuclear structures of the bulk powder samples were verified using time-of-flight neutron powder diffraction along with synchrotron X-ray powder diffraction. (57)Fe and (119)Sn Mössbauer spectroscopy confirmed the presence of Fe(2+) and Sn(4+) as well as the number of crystallographically unique positions. LIGS and LITS are semiconductors with indirect and direct bandgaps of 1.42 and 1.86 eV, respectively, according to optical diffuse-reflectance UV-vis-NIR spectroscopy.
Li2FeGeS4（LIGS）和Li2FeSnS4（LITS）是最早具有纤锌矿-凯斯特石结构的磁性半导体，分别表现出反铁磁性，奈尔温度TN约为6 K和4 K。这两种化合物都经历了伴有磁滞现象的传统变磁转变；可逆的自旋翻转转变占主导。基于定波长中子粉末衍射数据，我们提出LIGS和LITS表现出共线磁结构，分别与传播矢量km = [1/2, 1/2, 1/2]和[0, 0, 0.546(1)]呈 commensurate和incommensurate关系。由于临界场与温度有关，这两种化合物表现出相似的磁相图。使用飞行时间中子粉末衍射以及同步加速器X射线粉末衍射对块状粉末样品的核结构进行了验证。（57）Fe和（119）Sn穆斯堡尔谱证实了Fe(2+)和Sn(4+)的存在以及晶体学上独特位置的数量。根据光学漫反射紫外-可见-近红外光谱，LIGS和LITS分别是间接带隙为1.42 eV和直接带隙为1.86 eV的半导体。
