為了達到記憶以及邏輯自旋元件中能耗之降低,目前發現可以利用鐵電屏障在磁性穿隧接面中所扮演的主動角色,使得磁性材料中的磁矩可以透過外加電場來進行調控.目前的理論模型及計算方法大多只專注在由鐵磁/鐵電/鐵磁所構成的多鐵穿隧接面中的穿隧磁阻(TMR)及穿隧電阻(TER)的研究,卻鮮少探討其非共線磁性組態下的自旋傳輸特性.因此,在這個研究中我們利用最近自主開發的“Junpy”程序,透過由第一原理計算出共線磁性組態下的漢米爾敦量加上非平衡格林函數的方法,來計算多鐵穿隧接面中的自旋轉移力矩(STT)以及類場自旋力矩(FLST)在非共線磁性組態下和外加電場之間的關係.我們相信這一套新開發的計算方法,可以針對次世代多重調控以及低能耗的自旋電子元件的開發和應用提供重要的資訊. ;To push for low-energy consumption memory and logic spintronics devices, a reversal of magnetization requiring only the application of an electric field can be achieved via a ferroelectric (FE) barrier as an active role in magnetic tunnel junction. A number of model and first-principles calculation have focused on the tunneling magnetoresistance (TMR) and tunneling electroresistance (TER) effects for FM/FE/FM multiferroeic tunnel junctions (MFTJs) in collinear magnetic configuration. This gives rise to a four-state resistance device where resistance can be switched both by electric and magnetic fields. However, only few theoretical model but nearly no DFT calculation is applied for the non-collinear spin transport in MFTJs, due to the difficulties of the self-consistent calculation in non-collinear magnetic configurations. In this project, our newly developed “Junpy” program, combining the first-principles calculated Hamiltonian in collinear magnetic configuration with the non-equilibrium Green’s function (NEGF) method and the unitary transformation to investigate the spin torque effect for FM/BaTiO3/FM and FM/nucleobases in DNA/FM MFTJs in non-collinear magnetic configuration. We believe that these results may open a new avenue for next-generation, multifunctional and low-energy consumption spintronics devices.
