Effects of underlayer on structures and magnetic properties of Fe<sub>65</sub>Co<sub>35</sub> alloy films

Fe<sub>100-<i>x</i></sub>Co<sub><i>x</i></sub> (<i>x</i> = 30–40) alloys have the highest saturation magnetizations, 4?<i>M</i><sub>s</sub> ? 24 kG (1 G 10<sup>–4</sup> T). Therefore, FeCo thin flms been widely used in microwave magnetic devices. However, as-deposited film has a large coercivity, which is attributed to magnetostriction and high magneto-crystalline anisotropy<i>.</i> On basis of maintaining magnetization, adding an appropriate underlayer simple effective method reduce coercivity facilitate field-induced in-plane uniaxial anisotropy. Since these kinds films are high-frequency environment, eddy current loss GHz band must be considered. For certain material, thinner film, lower is. at present, thickness ferromagnetic layer generally tens nanometers or even hundreds nanometers, will not help suppress frequency. In present study, obtain with good soft properties excellent characteristics, Fe<sub>65</sub>Co<sub>35</sub> alloy 13 nm different underlayers (Cu, Co Ni<sub>80</sub>Fe<sub>20</sub>) prepared by magnetron sputtering. The effects materials NiFe values on structures studied. results show that introduction can increase anisotropies films, significantly improved. reason why achieved grain refinement, dipolar interaction between layers, reduction surface roughness. same thickness, obviously improve films: covercivity easy axis 23 Oe. By changing underlayer, dynamic adjusted. resonance frequency changes from 3.13 for NiFe(1 nm)/FeCo(13 nm) 2.78 NiFe(9.3 nm)/ FeCo(13 film. all NiFe/FeCo bilayer real part permeability <i>??</i> low value 350–450, damping coefficient <i>?</i> shows small 0.01–0.02. addition, smaller loss, contributes its application