High-Frequency Magnetic Properties Of Antiferromagnetic Coupling CoIr/Ru/CoIr Trilayers With Planar Magnetocrystalline Anisotropy

Soft magnetic films play an important role in electronic devices because of their small volumes and excellent high-frequency magnetic properties.With the development of technology,electronic devices demand that soft magnetic films should own higher resonance frequencies and higher initial permeability.The resonance frequencies of antiferromagnetic coupling ferromagnet/nonmagnet/ferromagnet trilayers can break through 10 GHz with the help of antiferromagnetic coupling effect.In other words,it can greatly improve the resonance frequencies of films by introducing the antiferromagnetic coupling effect.However,the initial permeability of these trilayers is very low because the equivalent antiferromagnetic coupling field is an in-plane equivalent field.Hence,how to improve the initial permeability and keep the high resonance frequencies of these trilayers is a worthy problem.According to the previous reports,oriented hcp-CoIr alloy soft magnetic films with easy magnetization crystal face（planar magnetocrystalline anisotropy）can break through Acher’s limit and improve the high-frequency magnetic properties because the magnetic moments are restricted further in the c-plane.Therefore,we prepare to introduce the magnetocrystalline anisotropy into antiferromagnetic coupling ferromagnet-/nonmagnet/ferromagnet trilayers with the help of hcp-CoIr soft magnetic alloy with planar magnetocrystalline anisotropy in order to improve the initial permeability and the resonance frequencies of these trilayers simultaneously.The main results are as follows:（1）Regulation of the antiferromagnetic coupling strength by the thickness of Ru interlayer.A series of CoIr（45 nm）/Ru/CoIr（45 nm）trilayers with the thickness of Ru interlayer changed from 0.4 nm to 1.2 nm were prepared.The results show that the antiferromagnetic coupling strength decreases with the increasing thickness of Ru interlayer.At the same time,according to the results of previous reports,the thickness range of Ru layer is around 0.3～0.4 nm for the strongest antiferromagnetic coupling strength of the trilayers.（2）Improvement of high-frequency magnetic properties in antiferromagnetic coupling trilayers by planar magnetocrystalline anisotropy.Based on（1）,the antiferromagnetic coupling Co₈₂Ir₁₈（35 nm）/Ru（0.35 nm）/Co₈₂Ir₁₈（35 nm）trilayers with planar magnetocrystalline anisotropy was prepared.The resonance frequency is increased from 3.80 GHz（CoIr single film）to 8.16 GHz.According to the calculated results,the initial permeability of our trilayer is the largest compared with other Co-based antiferromagnetic coupling trilayers without planar magnetocrystalline anisotropy.Introducing the planar magnetocrystalline anisotropy can make the antiferromagnetic coupling trilayers break through Acher’s limit and improve their high-frequency magnetic properties.（3）The preparation and exploration of antiferromagnetic coupling[CoIr/Ru/CoIr]_nsuperlattice films with planar magnetocrystalline anisotropy.In order to satisfy the need of practical devices for magnetic flux,[CoIr/Ru/CoIr/Au]_n superlattice films with Au as separation layers are studied.Firstly,the superlattice films with Au as the separation layer maintain strong planar magnetocrystalline anisotropy（out-of-plane anisotropic field around 19.50 k Oe）,good high-frequency magnetic properties（the initial permeability and resonance frequency around 18 and 10 GHz,respectively）and strong magnetic flux signal.However,the eddy current effect is relatively obvious because the superlattice films are too thick.In order to suppress the eddy current,Further research is needed.