P412
886-2-2789-6767
leesf [at] phys.sinica.edu.tw
P412
886-2-2789-6767
leesf [at] phys.sinica.edu.tw
Tseng, Yu-Ping / 886-2-2789-6754
(1) | 西元年:2011 研究人員(中):李尚凡、黃斯衍,王維綱,郭瑞年,李尚凡,錢嘉陵 研究人員(英):LEE, SHANG-FAN, S. Y. Huang, W. G. Wang, J. Kwo, Shang-Fan Lee, and C. L. Chien 研究成果名稱(中):自旋電子學中自旋傳輸力矩轉移與本徵自旋相關熱傳輸效應 研究成果名稱(英):Spin transfer torque and intrinsic spin-dependent thermal transport in Spintronics 簡要記述(中):自旋電子學的發展始於巨磁阻效應的發現,而後發展出許多面向。相關新穎材料的研發、以及許多的物理效應,例如穿隧磁阻、自旋轉移力矩、自旋霍爾效應、自旋泵、反向自旋效應等等都是很好的例子。其中基礎的觀念就是除了傳統利用電子的電性傳輸現象以外,還希望加入電子自旋作為研究與操控的目標。電子電路不斷的微小化,使得自旋轉移力矩與焦耳熱效應成了非常重要的課題。如果能夠研究出方法捨棄傳統電荷流而改採自旋流作為電子電路的基礎,熱傳輸效應可能不會再是科技發展的障礙,而成為主要的動力。 新興的自旋卡路里效應吸引了科學界的注意。因為磁性材料中不同自旋電子的化學位能會隨溫度而改變。當溫度梯度存在磁性金屬樣品中就會產生電子自旋流,但是因為沒有直接觀測的方式,須經由相鄰的鉑細線中產生的反向自旋效應即可偵測到。但是在磁性半導體與磁性絕緣體中,磁振子-聲子經由薄膜樣品基板的交互作用扮演了更重要的角色。我們的工作說明了樣品基板在熱傳導實驗中至關重要。在不同樣品形狀與不同溫度梯度的情形下,我們證明了垂直膜面的溫度梯度所導致的異常能斯特效應是所觀察到訊號的主要成因。在懸空、無基板的狀況下,本徵自旋相關熱傳輸現象才能呈現。 簡要記述(英):Spintronics has evolved, since the discovery of Giant Magnetoresistance effect, in many aspects including material developments, effects like Tunneling Magnetoresistance, Spin Transfer Torque, Spin Hall, Spin Pumping, Inverse Spin Hall, and more. The underlying idea was to investigate and manipulate the electron spin degree of freedom in addition to its charge in transport phenomena. However, electron charge transport is usually accompanied by spin transfer torque and Joule heating as the sizes of the electronics continues to shrink. Thus, devices that manipulate pure spin currents can be highly beneficial compared to traditional charge-based electronics, and we can exploit the interaction between heat transport and the charge/spin carriers. Spin caloritronic effect, such as spin Seebeck effect, has attracted a great deal of attention recently. The difference in the chemical potentials of the spin-up and the spin-down electrons can cause a pure spin current. This pure spin current can be detected by Pt strips via the inverse spin-Hall effect. In most cases such studies have been made on ferromagnetic thin films on substrates. The mechanism of spin Seebeck effect has evolved from the above-mentioned intrinsic difference in the spin chemical potentials when it was first reported experimentally to magnon-phonon interaction through the substrate in recent publication. We use patterned ferromagnetic thin film to demonstrate the profound effect of a substrate on the spin-dependent thermal transport. With different sample patterns and on varying the direction of temperature gradient, both longitudinal and transverse thermal voltages exhibit asymmetric instead of symmetric spin dependence. This unexpected behavior is due to an out-of-plane temperature gradient imposed by the thermal conduction through the substrate and the mixture of the anomalous Nernst effects. Only with substrate-free samples have we determined the intrinsic spin-dependent thermal transport with characteristics and field sensitivity similar to those of anisotropic magnetoresistance effect.
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