磁性薄膜材料中的交换耦合

Exchange Couplings in Magnetic Films

介绍了在磁性薄膜材料中的交换耦合的研究进展。制备了铁磁/反铁磁/铁磁3层结构不同成分的薄膜。利用X射线粉末衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)等测试分析技术,系统研究了磁性多层薄膜的相组成、界面及微观结构等。利用超导量子干涉仪(SQUID)研究薄膜的磁、电性能和交换耦合。在Co/反铁磁/Fe结构中发现了非常明显的与温度相关的铁磁/反铁磁界面耦合与铁磁/铁磁层间耦合之间的竞争效应。含有不同铁磁层Fe、Co、Fe20Ni80的3层膜FM1/Cr2O3/FM2对交换耦合随温度的变化存在较强的影响,发现铁磁层的磁晶各向异性和跟Cr2O3接触的自旋非对称性反射系数体系的界面和层间耦合有很大的影响。铁磁层对FM/AFM的交换耦合强度的影响甚大,这种影响和铁磁层的各向异性的相关性要强于和铁磁层饱和磁化强度的相关性。通过面内预加场和场冷的方式,在易轴互相垂直的[Pt/Co]n/NiFe/NiO异质结中实现了交换偏置的4种状态,可等温调控偏置。研究了Co/NiO反点阵列和连续膜的交换偏置,与连续膜相比,纳米反点阵列既能增大偏置,也能减小偏置,具有更高的热稳定性。

This article introduces recent advances in study of exchange couplings in magnetic films. The Ferromagnetic （ FM ）/Antiferromagnetic （AF）/Ferromagnetic （ FM ） trilayers are prepared by magnetron sputtering. Component, interface and microstructure of magnetic films were characterized by X-ray diffraction （XRD）, scanning electron microscope （SEM）, transmission electron microscopy （TEM）, etc. Magnetic and magnetotransport properties were characterized by superconducting quantum interference device （SQUID）. The competition between interlayer and interfacial exchange cou- plings is found to be temperature dependent in Co / AF / Fe trilayers. The strong effects of ferromagnetic materials on ex- change couplings are observed at different temperatures in FM1/Cr2O3/FM2 trilayers with FM containing Co, Fe or Ni80Fe20. The changes of anisotropy of FM and spin-asymmetry of the reflection coefficients for FM contacted antiferromag- netic layer greatly influence the strengths of interfacial and interlayer couplings of the trilayers. Strong effects of ferromag- netic layers on exchange coupling of FM/AF bilayer are observed, which are related to anisotropy of FM more strongly than saturation magnetization. Through magnetic field cooling and applying set magnetic field, four states of exchange bias have been achieved in [ Pt/Co]/NiFe/NiO heterostructures with orthogonal easy axes, and also the isothermal tunable exchange bias has been obtained. The exchange bias in the Co/NiO antidot arrays and continuous films has been investigated. Com- pared with the continuous films, an enhanced or decreased exchange bias field and a higher thermal stability have been found in the antidot arrays.