Magnetic properties of undoped Cu2O fine powders with magnetic impurities and/or cation vacancies
Magnetic properties of undoped Cu2O fine powders with magnetic impurities and/or cation vacancies
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DOI：
10.1088/0953-8984/21/14/145601
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发表时间：
2009-04-08
影响因子：
2.7
通讯作者：
Li, Yadong
中科院分区：
文献类型：
--
作者：
Chen, Chinping;He, Lin;Li, Yadong
采用不同的化学方法合成了三种不同尺寸和形貌的微米和亚微米级未掺杂的Cu_2 O半导体粉末。这些样品包括直径为200 nm的纳米球、尺寸为1 μ m的八面体和尺寸为800 nm的多面体。它们表现出广泛的磁性。在低温（T = 5 K）下，八面体样品是抗磁性的，磁化率chi（OH）= -9.5 × 10（-6）emu g（-1）Oe（-1）。纳米球是顺磁性的，chi（NS）= 2.2 x 10（-5）emu g（-1）Oe（-1）。另外两个多面体样品在不同的运行通过相同的过程中合成的发现，显示出不同的磁性。其中一个样品表现出弱铁磁性，T = 5 K时的Tc近似于455 K，饱和磁化强度MS近似于0.19emu g（-1），而另一个样品表现出顺磁性，chi = 1.0 × 10（-5）emu g（-1）Oe（-1）。从检测到的Fe、Co和Ni的杂质浓度估计的总磁矩太小，不能解释观察到的一到两个数量级的磁性。密度泛函理论（DFT）的计算表明，在Cu 2 O晶格中的阳离子空位是感生磁矩的可能原因之一。结果进一步预测，缺陷引起的磁矩有利于铁磁耦合的基态，如果局部浓度的阳离子空位，n（C），超过12.5%。这为解释观测到的磁性提供了一个可能的方案。在目前的工作中，特别是在理论计算的调查的局限性，进行了讨论，并提出了进一步研究的可能领域。
Fine powders of micron- and submicron-sized particles of undoped Cu2O semiconductor, with three different sizes and morphologies, have been synthesized by different chemical processes. These samples include nanospheres 200 nm in diameter, octahedra of size 1 mu m and polyhedra of size 800 nm. They exhibit a wide spectrum of magnetic properties. At low temperature, T = 5 K, the octahedron sample is diamagnetic with the magnetic susceptibility chi(OH) = -9.5 x 10(-6) emu g(-1) Oe(-1). The nanosphere is paramagnetic with chi(NS) = 2.2 x 10(-5) emu g(-1) Oe(-1). The other two polyhedron samples synthesized in different runs by the same process are found to show different magnetic properties. One of them exhibits weak ferromagnetism with T-C similar to 455 K and saturation magnetization MS similar to 0.19 emu g(-1) at T = 5 K, while the other is paramagnetic with chi = 1.0 x 10(-5) emu g(-1) Oe(-1). The total magnetic moment estimated from the detected impurity concentration of Fe, Co and Ni, is too small to account for the observed magnetism by one to two orders of magnitude. Calculations by density functional theory (DFT) reveal that cation vacancies in the Cu2O lattice are one of the possible causes of induced magnetic moments. The results further predict that the defect-induced magnetic moments favour a ferromagnetically coupled ground state if the local concentration of cation vacancies, n(C), exceeds 12.5%. This offers a possible scenario to explain the observed magnetic properties. The limitations of the investigations in the present work, in particular in the theoretical calculations, are discussed and possible areas for further study are suggested.