arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2004.05025cond-mat.mtrl-sciphysics.app-ph
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磁性隧道结的离子束改性

Ion beam modification of magnetic tunnel junctions

B. M. S. Teixeira, A. A. Timopheev, N. Caçoilo, L. Cuchet, J. Mondaud, J. R. Childress, S. Magalhães, E. Alves, N. A. Sobolev

摘要:

采用铁磁共振、振动样品磁强计和面内电流隧穿技术研究了400 keV $Ar^+$离子辐照对面内磁化磁性隧道结(MTJ)叠层磁、电性能的影响。辐照引起的磁各向异性,耦合能量和隧道磁阻(TMR)的变化表现出相关的依赖于离子注量,这使我们能够区分两种辐照制度。在低注量区域,$Φ < 10^{14} cm^{-2}$,保持了具有功能性MTJ所需的参数:在饱和磁化强度$M_S$的小幅降低之后,FeCoB自由层(FL)的各向异性被微弱地调制; TMR连续降低;层间交换耦合(IEC)和交换偏置(EB)略微降低。在高通量区域,$Φ > 10^{14} cm^{-2}$,MTJ被呈现为非磁性:FL各向异性的调制是强的,这是由$M_S$的强烈降低引起的,归因于FL和Ta盖层之间的高度界面混合; EB和IEC也丢失,可能是由于构成合成反铁磁体的层的混合;由于MgO阻挡层和MgO/FeCoB界面的辐照劣化,TMR消失。我们表明,周围的FL层起着决定性的作用,在确定的磁各向异性演变的趋势导致的照射,并且存在一个离子注量窗口,这样的调制的磁各向异性可以发生,而不会失去的TMR或磁配置的MTJ。

英文摘要:

The impact of 400 keV $Ar^+$ ion irradiation on the magnetic and electrical properties of in-plane magnetized magnetic tunnel junction (MTJ) stacks was investigated by ferromagnetic resonance, vibrating sample magnetometry and current-in-plane tunneling techniques. The irradiation-induced changes of the magnetic anisotropy, coupling energies and tunnel magnetoresistance (TMR) exhibited a correlated dependence on the ion fluence, which allowed us to distinguish between two irradiation regimes. In the low-fluence regime, $Φ < 10^{14} cm^{-2}$, the parameters required for having a functioning MTJ were preserved: the anisotropy of the FeCoB free layer (FL) was weakly modulated following a small decrease in the saturation magnetization $M_S$; the TMR decreased continuously; the interlayer exchange coupling (IEC) and the exchange bias (EB) decreased slightly. In the high-fluence regime, $Φ > 10^{14} cm^{-2}$, the MTJ was rendered inoperative: the modulation of the FL anisotropy was strong, caused by a strong decrease in $M_S$, ascribed to a high degree of interface intermixing between the FL and the Ta capping; the EB and IEC were also lost, likely due to intermixing of the layers composing the synthetic antiferromagnet; and the TMR vanished due to the irradiation-induced deterioration of the MgO barrier and MgO/FeCoB interfaces. We demonstrate that the layers surrounding the FL play a decisive role in determining the trend of the magnetic anisotropy evolution resulting from the irradiation, and that an ion-fluence window exists where such a modulation of magnetic anisotropy can occur, while not losing the TMR or the magnetic configuration of the MTJ.

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