Uncoupled surface spin induced exchange bias in α-MnO2 nanowires.
Uncoupled surface spin induced exchange bias in α-MnO2 nanowires.
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DOI：
10.1038/srep06641
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发表时间：
2014-10-16
影响因子：
4.6
通讯作者：
Dou S
中科院分区：
文献类型：
--
作者：
Li W;Zeng R;Sun Z;Tian D;Dou S
我们研究了二氧化锰纳米线的微观结构、表面状态、价态波动、磁性能和交换偏置效应。采用微波辅助水热法制备了高纯度α-MnO2矩形纳米线。显微结构分析表明，纳米线以（21 0）平面为表面，沿[0 0 1]方向生长。x射线光电子能谱分析未发现Mn3+和Mn2+离子。锰离子的有效磁矩与Mn4+的理论值和实验值吻合得很好。在粗糙表面的MnO6八面体中，Mn4+离子在3d3轨道上的不耦合自旋是净磁矩的原因。通过磁测量观察自旋玻璃的行为。此外，由于表面自旋玻璃与反铁磁α-MnO2基体的耦合作用，首次在纯α-MnO2相中观察到交换偏置效应。这些α-MnO2纳米线具有类似自旋玻璃的行为，并且在不耦合的表面自旋激发下具有交换偏置效应，因此应该激发对纳米结构中表面结构诱导磁性的起源、理论和适用性的进一步研究。
We have studied the microstructure, surface states, valence fluctuations, magnetic properties, and exchange bias effect in MnO2 nanowires. High purity α-MnO2 rectangular nanowires were synthesized by a facile hydrothermal method with microwave-assisted procedures. The microstructure analysis indicates that the nanowires grow in the [0 0 1] direction with the (2 1 0) plane as the surface. Mn3+ and Mn2+ ions are not found in the system by X-ray photoelectron spectroscopy. The effective magnetic moment of the manganese ions fits in with the theoretical and experimental values of Mn4+ very well. The uncoupled spins in 3d3 orbitals of the Mn4+ ions in MnO6 octahedra on the rough surface are responsible for the net magnetic moment. Spin glass behavior is observed through magnetic measurements. Furthermore, the exchange bias effect is observed for the first time in pure α-MnO2 phase due to the coupling of the surface spin glass with the antiferromagnetic α-MnO2 matrix. These α-MnO2 nanowires, with a spin-glass-like behavior and with an exchange bias effect excited by the uncoupled surface spins, should therefore inspire further study concerning the origin, theory, and applicability of surface structure induced magnetism in nanostructures.
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影响因子：
4.6
作者：
Kohn, A.;Kovacs, A.;Fan, R.;McIntyre, G. J.;Ward, R. C. C.;Goff, J. P.
通讯作者：
Goff, J. P.
影响因子：
41.2
作者：
Ali, Mannan;Adie, Patrick;Stamps, Robert L.
通讯作者：
Stamps, Robert L.
影响因子：
8.6
作者：
Hoffmann, A
通讯作者：
Hoffmann, A
影响因子：
3.7
作者：
Keller, J;Miltényi, P;Usadel, KD
通讯作者：
Usadel, KD
影响因子：
2.7
作者：
LIN, D;NUNES, AC;BERKOWITZ, AE
通讯作者：
BERKOWITZ, AE