Effects of underlayer on structures and magnetic properties of Fe65Co35 alloy films
Effects of underlayer on structures and magnetic properties of Fe65Co35 alloy films
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DOI：
10.7498/aps.71.20220476
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发表时间：
2022-08-05
影响因子：
1
通讯作者：
Zheng Fu
中科院分区：
文献类型：
--
作者：
Han Ze-Yu;Song Cheng-Ji;Zheng Fu
Fe 100-xCox（x = 30-40）合金具有最高的饱和磁化强度，4 π M-s >> 24 kG（1 G = 10（-4）T）。因此，FeCo薄膜在微波磁性器件中得到了广泛的应用。然而，沉积态的FeCo薄膜具有大的矫顽力，这归因于大的饱和磁致伸缩和高的磁晶各向异性。在保持高饱和磁化强度的基础上，添加合适的底层是降低薄膜介电常数、促进磁场诱导面内单轴磁各向异性的简单有效的方法。由于这类薄膜用于高频环境，必须考虑GHz频段的涡流损耗。对于一定的薄膜材料，薄膜越薄，涡流损耗越低。但目前铁磁层的厚度一般为几十纳米甚至几百纳米，这将无助于抑制高频下的涡流损耗。为了获得具有良好软磁性能和高频特性的FeCo薄膜，采用磁控溅射法制备了厚度为13 nm的Fe 65 Co 35合金薄膜，并采用不同的底层（Cu、Co和Ni 80 Fe 20）进行了制备。研究了不同底层材料和不同NiFe底层厚度对FeCo薄膜结构和磁性能的影响。结果表明，衬层的引入增加了薄膜的面内单轴磁各向异性，薄膜的软磁性能得到显著改善。晶粒细化、层间偶极相互作用和表面粗糙度降低是获得良好软磁性能的原因。对于相同厚度的不同底层材料，NiFe底层可以明显改善FeCo薄膜的软磁性能，其易磁化轴的覆盖率为23 Oe，通过改变NiFe底层的厚度，可以调节薄膜的动态磁性能。NiFe（1 nm）/FeCo（13 nm）薄膜的谐振频率从3.13GHz变为2.78GHz。对于所有的NiFe/FeCo双层膜，在低频下磁导率μ '的真实的部分具有350-450的大值，并且阻尼系数α显示0.01-0.02的小值。此外，较小的膜厚可以降低涡流损耗，有助于其在高频微波磁性器件中的应用。
Fe100-xCox (x = 30-40) alloys have the highest saturation magnetizations, 4 pi M-s >> 24 kG (1 G = 10(-4) T). Therefore, FeCo thin flms have been widely used in microwave magnetic devices. However, the as-deposited FeCo film has a large coercivity, which is attributed to the large saturation magnetostriction and high magnetocrystalline anisotropy. On the basis of maintaining high saturation magnetization, adding an appropriate underlayer is a simple and effective method to reduce the coercivity of the film and facilitate the magnetic field-induced in-plane uniaxial magnetic anisotropy. Since these kinds of films are used in a high-frequency environment, the eddy current loss in GHz band must be considered. For a certain film material, the thinner the film, the lower the eddy current loss is. However, at present, the thickness of ferromagnetic layer is generally tens of nanometers or even hundreds of nanometers, which will not help to suppress the eddy current loss at high frequency. In the present study, to obtain FeCo films with good soft magnetic properties and excellent high-frequency characteristics, Fe65Co35 alloy films with a thickness of 13 nm and different underlayers (Cu, Co and Ni80Fe20) are prepared by magnetron sputtering. The effects of different underlayer materials and different NiFe underlayer thickness values on the structures and magnetic properties of FeCo films are studied. The results show that the introduction of underlayers can increase the in-plane uniaxial magnetic anisotropies of films, and the soft magnetic properties of films are significantly improved. The reason why the good soft magnetic properties can be achieved is attributed to the grain refinement, the dipolar interaction between layers, and the reduction of surface roughness. For different underlayer materials with the same thickness, NiFe underlayer can obviously improve the soft magnetic properties of FeCo films: the covercivity of easy axis is 23 Oe. By changing the thickness of NiFe underlayer, the dynamic magnetic properties of films can be adjusted. The resonance frequency changes from 3.13 GHz for NiFe(1 nm)/FeCo(13 nm) film to 2.78 GHz for NiFe(9.3 nm)/FeCo(13 nm) film. For all NiFe/FeCo bilayer films, the real part of the permeability mu' at low frequency has a large value of 350-450, and the damping coefficient alpha shows a small value of 0.01-0.02. In addition, the smaller film thickness can reduce eddy current loss, which contributes to its application in high-frequency microwave magnetic devices.