The effect of interface roughness of ferromagnetic and antiferromagnetic layers on exchange bias is still not well understood. In this report we have investigated the effect of surface roughness in (111)-oriented antiferromagnetic CoO films on exchange bias with ferromagnetic Fe grown on top. The surface roughness is controlled at the atomic scale, over a range below ~ 0.35 nm, by varying layer thickness of the CoO films. It is observed that both exchange bias field ($H_{E}$) and coercivity ($H_{C}$) extensively depend on the atomic scale roughness of the CoO (111) at the interface with Fe film. An opposite dependence of $H_{E}$ and $H_{C}$ on interface roughness was found, which was ascribed to partially compensated spin states induced by the atomic roughness at the fully uncompensated CoO (111) surfaces and was corroborated using the Monte Carlo simulations. Moreover, the onset temperature for $H_{C}$ is found to be up to ~ 80 K below the blocking temperature ($T_{B}$) and the temperature dependence of $H_{C}$ follows the power law with a critical exponent equal to one, which indicates that, in this system, $H_{C}$ is more of an interface-related property than $H_{E}$.
Interfacial roughness and proximity effects in superconductor/ferromagnet CuNi/Nb heterostructures
本文报道了用磁控溅射法制备的Nb/Cu $_{60}$ Ni $_{40}$混合超导/铁磁体（S/F）双层膜的结构和电子性质。X射线和中子反射测量表明，沉积在Al $_2$ O $_3$（1 $\bar{1}$ 02）衬底上的异质结构的总界面粗糙度和不同界面粗糙度的垂直相关性都低于沉积在Si（111）衬底上的异质结构。互感实验研究了界面粗糙度对超导转变温度$T_C$的影响。这些测量结果表明，沉积在Al $_2$ O $_3$上的异质结构中的$\sim$比沉积在Si上的异质结构高$T_C$ 4%。我们将这种效应归因于S层中电子的更高平均自由程，这是由界面处的扩散散射的抑制引起的。然而，$T_C$对铁磁层厚度的依赖性在两个系统中没有显著差异，表明库珀对的透明性上的界面粗糙度的微弱影响。
Ion irradiation and implantation modifications of magneto-ionically induced exchange bias in Gd/NiCoO
通过离子迁移对磁特性的磁离子控制已经显示出在节能自旋电子器件中实现新功能的希望。本文研究了氦离子辐照和氧离子注入对Gd/Ni $_{0.33}$ Co $_{0.67}$ O异质结磁致交换偏置效应的影响。使用$He^+$的辐照由于应变弛豫导致Ni $_{0.33}$ Co $_{0.67}$ O晶格的膨胀。在低He+通量（$\leq$ 2 $\times$ 10 $^{14}$ ions cm $^{-2}$）下，由于增强的氧迁移，氧化还原诱导的界面磁矩最初增加。在较高的能量密度下，交换偏置由于钉扎的未补偿界面Ni $_{0.33}$ Co $_{0.67}$ O自旋的减少而被抑制。对于氧注入的样品，初始晶格膨胀低于5 $\times$ 10 $^{15}$ cm $^{-2}$的剂量，随后在较高的剂量由晶格收缩和相分离成NiO和CoO富相，这反过来又改变了交换偏置占主导地位。这些结果突出了离子辐照和注入的可能性，作为一种有效的手段来定制磁离子效应。
