Abstract
Crystallographic orientation dependence of Gilbert damping constant, α , has been measured under different static magnetic fields for Fe70 Co30 (100) single-crystal thin film samples prepared at various substrate temperatures. Lorentz type resonance peaks are observed for the samples prepared below 200 oC. For a sample deposited at 400 oC, broadening of the resonance peak is observed, which is related with an increased surface roughness. α value decreases monotonically with increasing the static field when the field is applied parallel to the easy magnetization axis, whereas it increases when the field is applied along the hard magnetization axis up to around the anisotropy field and then decreases. The minimum value of α is determined to be 0.012 for the hard axis under static fields greater than 650 Oe. The value is twice larger compared with that of Fe(100) single-crystal film. The static magnetization curves measured for Fe70 Co30 films show large deviations from the curves expected by coherent rotation mode. Such deviation seems to be a possible reason for a larger α value of Fe70 Co30 thin film.
Highlights
Understanding the dynamic magnetization process in magnetic thin films is strongly required for developments of high-frequency magnetic devices such as magnetic recording heads and random access memory devices [1, 2]
Dynamic magnetic properties at arbitrary magnetization states of a sample are important for the actual devices which operate under various magnetic fields [8]
Ferromagnetic resonance (FMR) signals are observed by using a vector network analyser (VNA) technique under various magnetic fields
Summary
Understanding the dynamic magnetization process in magnetic thin films is strongly required for developments of high-frequency magnetic devices such as magnetic recording heads and random access memory devices [1, 2]. One is the method using a microwave cavity where the FMR line width is measured by sweeping the magnetic filed at a fixed frequency [3, 4]. The other is the method employing a vector network analyser (VNA) where the frequency is swept under a fixed magnetic field [5,6,7]. FMR signals are observed by using a VNA technique under various magnetic fields. Dynamic magnetic properties of Fe70Co30(100) single-crystal thin film are investigated by broadband FMR employing a VNA [7]. In order to investigate the effect of crystallographic quality on dynamic magnetic properties, Fe70Co30 films are prepared by changing the substrate temperature. The dynamic properties are compared with those of Fe(100) single-crystal film in order to clarify the effects of extrinsic factors
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