Formation of midgap states and ferromagnetism in semiconductingCaB6
Formation of midgap states and ferromagnetism in semiconductingCaB6
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DOI：
10.1103/physrevb.69.113202
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发表时间：
2004-03
影响因子：
3.7
通讯作者：
B. Cho;J. Rhyee;B. Oh;M. Jung;H. Kim;Y. Yoon;J. Kim;T. Ekino
中科院分区：
文献类型：
--
作者：
B. Cho;J. Rhyee;B. Oh;M. Jung;H. Kim;Y. Yoon;J. Kim;T. Ekino
基于我们对高质量缺陷控制单晶的联合输运、光学和隧道测量，我们给出了CAB6中电子结构和铁磁相互作用的一致总体图景。用99.9999%纯硼合成的纯CaB6单晶具有完全半导体特性，如2-300K的单调电阻、隧道电导带隙和1.0 eV的光吸收阈值。用99.9%纯硼诱导的中能带态在导带下方0.18 eV和额外的自由载流子合成的CaB6单晶中形成了与硼有关的缺陷，其输运、光学和隧道性质都有很大的改善。值得注意的是，无论化学计量比如何，用99.9999%纯硼制备的单晶都没有检测到铁磁信号，而用99.9%纯硼制备的单晶在有限的载流子密度范围内表现出铁磁性。我们将讨论电子态和磁化强度之间可能的猜测。
We present a consistent overall picture of the electronic structure and ferromagnetic interaction in CaB 6, based on our joint transport, optical, and tunneling measurements on high-quality defect-controlled single crystals. Pure CaB 6 single crystals, synthesized with 99.9999% pure boron, exhibited fully semiconducting characteristics, such as monotonic resistance for 2–300 K, a tunneling conductance gap, and an optical absorption threshold at 1.0 eV. Boron-related defects formed in CaB 6 single crystals synthesized with 99.9% pure boron induced midgap states 0.18 eV below the conduction band and extra free charge carriers, with the transport, optical, and tunneling properties substantially modified. Remarkably, no ferromagnetic signals were detected from single crystals made with 99.9999% pure boron, regardless of stoichiometry, whereas those made with 99.9% boron exhibited ferromagnetism within a finite range of carrier density. The possible surmise between the electronic state and magnetization will be discussed.