Department of Physics, National and Kapodistrian, University of Athens, Athens, GR-15784, Greece.
Nanotechnology. 2017 Jul 14;28(28):285701. doi: 10.1088/1361-6528/aa77e3. Epub 2017 Jun 7.
We study the magnetic properties of cylindrical ferromagnetic core-antiferromagnetic shell nanowires using Monte Carlo simulations and a classical Heisenberg Hamiltonian in order to elucidate the impact of the oxidized shell on the magnetic properties and the magnetization reversal mechanism. We find that the coupling to the antiferromagnetic shell leads to suppression of the coercivity and emergence of a weak exchange bias effect. Comparison of the magnetization reversal mechanism in the bare and the surface-oxidized nanowire reveals that the domain wall propagation and annihilation remains the dominant reversal mechanism in surface oxidized nanowires as in their ferromagnetic counterparts. However, the interface exchange coupling introduces a secondary reversal mechanism activated in the central part of the wire with characteristics of coherent rotation, which acts in synergy to wall propagation leading to enhancement of the wall mobility. This effect is more pronounced in nanowires with large exchange bias values and is attributed to the uncompensated interface moments that act as nucleation centers for magnetization reversal. Our results are in good agreement with recent measurements in Co and Co/CoO nanowires.
我们使用蒙特卡罗模拟和经典的海森堡哈密顿量研究了圆柱形铁磁芯-反铁磁壳纳米线的磁性质，以阐明氧化壳对磁性质和磁化反转机制的影响。我们发现，与反铁磁壳的耦合导致矫顽力的抑制和弱交换偏置效应的出现。在裸纳米线和表面氧化纳米线中磁化反转机制的比较表明，畴壁传播和湮灭仍然是表面氧化纳米线中主要的反转机制，就像在其铁磁对应物中一样。然而，界面交换耦合引入了一种在导线中心部分起作用的二次反转机制，其具有相干旋转的特征，与壁传播协同作用，导致壁迁移率的增强。这种效应在具有较大交换偏置值的纳米线中更为明显，这归因于作为磁化反转成核中心的未补偿界面磁矩。我们的结果与最近在 Co 和 Co/CoO 纳米线中的测量结果非常吻合。
