Department of Physics and Astronomy, Univ. of Delaware, Newark, DE 19716, USA.
Nanotechnology. 2016 Oct 28;27(43):43LT01. doi: 10.1088/0957-4484/27/43/43LT01. Epub 2016 Sep 22.
Nanomagnetic logic has emerged as a potential replacement for traditional Complementary Metal Oxide Semiconductor (CMOS) based logic because of superior energy-efficiency (Salahuddin and Datta 2007 Appl. Phys. Lett. 90 093503, Cowburn and Welland 2000 Science 287 1466-68). One implementation of nanomagnetic logic employs shape-anisotropic (e.g. elliptical) ferromagnets (with two stable magnetization orientations) as binary switches that rely on dipole-dipole interaction to communicate binary information (Cowburn and Welland 2000 Science 287 1466-8, Csaba et al 2002 IEEE Trans. Nanotechnol. 1 209-13, Carlton et al 2008 Nano Lett. 8 4173-8, Atulasimha and Bandyopadhyay 2010 Appl. Phys. Lett. 97 173105, Roy et al 2011 Appl. Phys. Lett. 99 063108, Fashami et al 2011 Nanotechnology 22 155201, Tiercelin et al 2011 Appl. Phys. Lett. 99 , Alam et al 2010 IEEE Trans. Nanotechnol. 9 348-51 and Bhowmik et al 2013 Nat. Nanotechnol. 9 59-63). Normally, circular nanomagnets are incompatible with this approach since they lack distinct stable in-plane magnetization orientations to encode bits. However, circular magnetoelastic nanomagnets can be made bi-stable with a voltage induced anisotropic strain, which provides two significant advantages for nanomagnetic logic applications. First, the shape-anisotropy energy barrier is eliminated which reduces the amount of energy required to reorient the magnetization. Second, the in-plane size can be reduced (∼20 nm) which was previously not possible due to thermal stability issues. In circular magnetoelastic nanomagnets, a voltage induced strain stabilizes the magnetization even at this size overcoming the thermal stability issue. In this paper, we analytically demonstrate the feasibility of a binary 'logic wire' implemented with an array of circular nanomagnets that are clocked with voltage-induced strain applied by an underlying piezoelectric substrate. This leads to an energy-efficient logic paradigm orders of magnitude superior to existing CMOS-based logic that is scalable to dimensions substantially smaller than those for existing nanomagnetic logic approaches. The analytical approach is validated with experimental measurements conducted on dipole coupled Nickel (Ni) nanodots fabricated on a PMN-PT (Lead Magnesium Niobate-Lead Titanate) sample.
纳米磁性逻辑作为传统互补金属氧化物半导体（CMOS）逻辑的潜在替代品而出现，因为它具有更高的能量效率（Salahuddin 和 Datta，2007 年，Appl. Phys. Lett. 90 093503；Cowburn 和 Welland，2000 年，Science 287 1466-68）。纳米磁性逻辑的一种实现方式采用形状各向异性（例如，椭圆形）的铁磁体（具有两个稳定的磁化方向）作为二进制开关，它们依赖于偶极子-偶极子相互作用来传递二进制信息（Cowburn 和 Welland，2000 年，Science 287 1466-8；Csaba 等人，2002 年，IEEE Trans. Nanotechnol. 1 209-13；Carlton 等人，2008 年，Nano Lett. 8 4173-8；Atulasimha 和 Bandyopadhyay，2010 年，Appl. Phys. Lett. 97 173105；Roy 等人，2011 年，Appl. Phys. Lett. 99 063108；Fashami 等人，2011 年，Nanotechnology 22 155201；Tiercelin 等人，2011 年，Appl. Phys. Lett. 99 ；Alam 等人，2010 年，IEEE Trans. Nanotechnol. 9 348-51；Bhowmik 等人，2013 年，Nat. Nanotechnol. 9 59-63）。通常，圆形纳米磁铁与这种方法不兼容，因为它们缺乏明显的稳定的面内磁化方向来编码位。然而，通过电压诱导各向异性应变可以使圆形磁弹性纳米磁铁具有双稳态，这为纳米磁性逻辑应用提供了两个显著的优势。首先，消除了形状各向异性能垒，从而减少了重新定向磁化所需的能量。其次，可以减小面内尺寸（约 20nm），这在以前由于热稳定性问题是不可能的。在圆形磁弹性纳米磁铁中，即使在这种尺寸下，电压诱导的应变也能稳定磁化，从而克服了热稳定性问题。在本文中，我们通过实验测量验证了一种由圆形纳米磁铁组成的阵列实现二进制“逻辑线”的可行性，该阵列通过底层压电衬底施加的电压诱导应变进行计时。这导致了一种能量效率极高的逻辑范例，其效率比现有基于 CMOS 的逻辑高出几个数量级，并且可扩展到比现有纳米磁性逻辑方法小得多的尺寸。该分析方法通过在 PMN-PT（铅镁铌酸铅-钛酸铅）样品上制造的偶极子耦合镍（Ni）纳米点的实验测量得到验证。
