具有负磁晶各向异性常数软磁薄膜的微波磁性

Microwave mangtic devices with high permeability at higher frequency are required with the development of information technology.However, the microwave magnetic properties of Fe- and Co-based soft films reported in the world currently are restricted by Acher limit due to that their out-of-plane anisotropy field is equal to the demagnetization field. In this kind of soft magnetic films, the enhancement of natural resonance frequency inevitably leads to the decrease of the permeability, which is not coincident with the trend of higher working frequency and miniaturization of magnetic electron devices. This project originally points out that the microwave magnetic properties of the soft magnetic film with negative crystalline anisotropy constant can exceed the Acher limit. This kind of soft magnetic film can maintain a high permeability at higher frequency. In experiment, the epitaxial growth of hcp structure of CoIr with negative crystalline anisotropy constant and with its c plane parallel to the film plane will be carried out. As the out-of-plane anisotropy field contains the field produced by crystalline anisotropy besides the demagnetization field, the natural resonance frequency could be enhanced dramatically. On the other hand,the permeabiltiy is irrelated to the crystalline anisotropy and still possess a high value. This project will support us a theoretical guidance and new materials to explore higher performance of devices made by microwave soft films.

信息技术的快速发展要求制备出在更高频率仍具有高磁导率的微波磁性器件。然而国内外现阶段研究的Fe及Co基等软磁薄膜，由于面外各向异性场等于退磁场，其微波磁性遵循Acher极限。在这些薄膜体系中，要提高薄膜的自然共振频率必然导致微波磁导率的降低，所以无法满足电子器件高频化和微型化的要求。本项目创新性地提出具有负磁晶各向异性常数的软磁薄膜的微波磁性可以超越Acher极限，能在提高自然共振频率的同时仍保持高的磁导率。实验上拟利用具有负磁晶各向异性常数的CoIr（hcp结构，c面为易磁化面）合金为原材料，通过控制使c面平行于膜面取向生长。此时，由于总的面外各向异性场由薄膜的退磁场和磁晶各向异性等效场叠加而成，薄膜的自然共振频率可以获得大幅提升；同时，该薄膜的微波磁导率不受磁晶各向异性的影响，仍具有高的值。该项目的研究能为研发更高性能的微波软磁薄膜器件提供理论指导和材料体系支撑。

软磁薄膜在高频技术领域有重要应用价值，例如微型电感、噪声抑制器、磁记录等。随着数据处理速度的增加和器件集成化发展，高频化和微型化是重要的发展趋势。对于普通的软磁薄膜（不考虑磁晶各向异性），其高频磁性遵从Arch极限，即共振频率的升高必然导致磁导率的降低，这对于器件的微型化发展很不利。因此，探寻能突破Arch极限的软磁薄膜，使得共振频率升高的同时仍保持高的磁导率，对于研发新一代高频软磁薄膜及满足电磁器件高频化、微型化的发展具有重要价值。本项目创造性地将强磁晶各向异性引入软磁薄膜，制备了取向生长的具有负磁晶各向异性常数的hcp结构Co1-xIrx合金薄膜。当Ir达到一定含量时，薄膜在面内保持软磁性能的同时，面外各向异性场由退磁场和磁晶各向异性场叠加而成,相比传统软磁薄膜有大幅度提升。本工作通过工艺摸索，成功制备了高取向度的Co1-xIrx薄膜；重点研究了Ir成对薄膜静态及高频磁性的影响，结果表明： x≥0.06 时，薄膜具有好的软磁性能，x≥0.14 时，薄膜的(μi-1)fr值均大于传统软磁薄膜的Arch极限，当x=0.2时，增加的百分比达到了42%；还研究了膜厚（最大厚度为270 nm）对薄膜静态和高频磁性的影响，随着薄膜的增加，软磁性能变好，磁矩进动阻尼系数逐渐减小。该工作为寻求在更高频率下工作的高磁导率软磁薄膜开辟了新思路。