Control of the electromagnetic properties of synthetic magnetic structures at gigahertz frequencies is advantageous for the simulation and design of components for high-frequency applications, such as shielding materials in magnetic recording. In such applications, it is desirable to have a high saturation magnetization, low coercivity, high permeability, and near-zero magnetostriction. A typical material is NixFe100-x, where x ~ 80 provides near-zero magnetostriction but relatively low magnetization. Multilayer structures such as Ni80Fe20/Ni20Fe80 may benefit some static properties such as magnetization while retaining low magnetostriction [1] and therefore will extend the parameter space. We present a systematic study of the ferromagnetic resonance (FMR) of sputter-deposited thin-film NiFe bilayers of the form NixFe100-x/NiyFe100-y using VNA-FMR [2], vibrating sample magnetometry and x-ray diffraction, with the purpose of investigating the relation between dynamic magnetic and microstructure properties of such structures. Of particular interest are layer combinations involving both fcc and bcc crystal structures since studies on single films of NixFe100-x have shown dramatically increased damping of the FMR when Ni content is reduced across the transition from fcc to bcc near x ~ 40, figure 1. A result that was not to be expected from the single-layer studies was that the FMR response of certain bilayers was strong even when the bcc NiFe layer was the dominant layer in the structure, figure 2. The possibility of incorporating the best properties of both layers in this way has significance for achieving an optimized material design. 
**References:** [1] C.B. Hill. “Manipulation and Magnetostriction of NiFe Films for Advanced Reader Shielding Application”, PhD Thesis, Queen’s University Belfast (2013) 
[2] Y. Ding, T. J. Klemmer and T. M. Crawford, J. Appl. Phys. Vol. 96, p.2969 (2004) 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/b5852ff51f9bfd694f13268e2842e1e2.png) 
Fig. 1: FMR spectra of 100nm NixFe100-x single layer thin films with x varying from 10 to 50 across the fcc/bcc phase transition boundary. Note that all measurements were performed at an applied field H=253Oe. 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/b76d6eeb3f1aa18965a3c31b5d4041ce.png) 
Fig. 2: FMR spectra of Ni80Fe20(60-t nm) / Ni20Fe80(t nm) thin films with varying bcc layer thickness, t. Note that all measurements were performed at an applied field of 253Oe. Magnetization trend and structure schematic is inset.

Towards Optimised Tunable NiFe Multilayers for High Frequency Applications

Tailoring and control of electromagnetic properties of synthetic magnetic structures is advantageous for high frequency applications, such as shielding materials in magnetic recording, where characterisation in the gigahertz frequency range is necessary to determine parameters for simulations and aid component design. In such applications it is desirable to have a high saturation magnetisation, low coercivity, high permeability and close to zero magnetostriction. Meeting almost all these requirements, NiFe is the material of choice for many high frequency applications. We present a systematic study of the ferromagnetic resonance (FMR) and spin wave properties of NixFe100-x alloy thin superlattice films of the form n[NixFe100-x/NiyFe100-y], where n is the number of bilayers. Films were fabricated by planar magnetron sputtering and the effects of deposition conditions were investigated. Magnetic and material properties were measured using FMR [1], vibrating sample magnetometer and x-ray diffraction, with the aim to determine any relation between microstructure and the static and dynamic magnetic properties. Layer compositions within the bilayers have been chosen with particular interest in fcc/bcc layer combinations such as Ni80Fe20/Ni20Fe80, which may have benefits for some static properties such as high magnetisation and low magnetostriction [2]. Studies on single layers have shown dramatic changes in FMR response across the fcc-bcc boundary near x = 40, figure 1. However, for bilayer films it was found that increasing the thickness of the bcc Ni20Fe80 layer in the structure increased the resonant frequency but did not significantly reduce the FMR signal, figure 2.

![](https://assets.underline.io/uploads/markdown_image/1/image/2d9c99cff6d1c85880be60efcc3b4eb1.jpg)

Fig. 1: FMR spectra of 100nm NixFe100-x single layer thin films with x varying from 10 to 60. Note that all measurements were performed at an applied field H=253Oe. XRD is inset.

![](https://assets.underline.io/uploads/markdown_image/1/image/80e55db23ea15b0120ab8fa67c4beb0e.jpg)

Fig. 2: FMR spectra of Ni80Fe20(60-t nm)/Ni20Fe80(t nm) thin films with t varying from 50 to 10. Note that all measurements were performed at an applied field of 253Oe. XRD is inset.

Ferromagnetic Resonance of Tuneable Low Magnetostrictive NixFe100-x Superlattice Structures for High Frequency Application

Tailoring and control of electromagnetic properties of synthetic magnetic structures is advantageous for high frequency applications, such as shielding materials in magnetic recording, where characterisation in the gigahertz frequency range is necessary to determine parameters for simulations and aid component design. In such applications it is desirable to have a high saturation magnetization, low coercivity, high permeability and close to zero magnetostriction. Meeting almost all of these requirements, NiFe is the material of choice for many high frequency applications. We present a systematic study of the effects of process settings, dopants and composition on the ferromagnetic resonance (FMR) and spin wave properties of NixFe100-x alloy thin films fabricated by magnetron sputtering and investigated using a coplanar waveguide, vector network analyser (VNA) [1], vibrating sample magnetometer (VSM) and x-ray diffraction (XRD), with the aim to determine any relation between microstructure and the static and dynamic magnetic properties. It has been found that changes in the NiFe crystal structure and deposition can have significant impact on the magnetic properties, examples of which can be seen in Fig. 1 and 2. This work extends into compositionally modulated superlattice structures to explore further possibilities with respect to material design and optimization [2]. VAMPIRE [3] atomistic simulations have been employed in conjunction with these experiments and to provide parameters for FMR simulations using the micromagnetic model, OOMMF [4].

**References:**

[1] Y. Ding et al. J. Appl. Phys. 96. (2004) [2] C.B. Hill et al. Meas. Sci. Technol. 24. (2013) [3] R.F.L. Evans et al. J. Phys.: Condens. Matter 26, 103202 (2014) [4] M. J. Donahue and D. G. Porter, “OOMMF User’s Guide, Version 1.0,” NISTIR 6376, National Institute of Standards and Technology, Gaithersburg, MD (Sept 1999).

**Images:**

![](https://assets.underline.io/uploads/markdown_image/1/image/ca3c03d9e435df9d90ed1b8a3bcadece.jpg)
Fig. 1 : FMR spectra at an applied field of 253Oe showing the broadening of the FMR and therefore increased damping with increasing Fe content in NixFe100-x thin films. Note particularly the most significant changes occur at x=40 which marks the fcc/bcc transition.

![](https://assets.underline.io/uploads/markdown_image/1/image/f564dafe40ca24a0b86a77ae748d9a43.jpg)
Fig. 2 : FMR spectra at an applied field of 253Oe illustrating the effect of increasing substrate temperature during deposition on Ni80Fe20, where a supression of the FMR response is seen at 300°C and above.

 Control of Static and Dynamic Magnetic Properties of NixFe100-x Alloy Thin Films

Tailoring the electromagnetic properties of synthetic magnetic structures is advantageous for high frequency applications, such as engineering shielding materials in magnetic recording where control of properties such as permeability is essential. Design of suitable components requires the characterisation of materials in the gigahertz frequency range to determine the parameters necessary for simulations. We present a systematic study of the dependence of the ferromagnetic resonance (FMR) and spin wave properties of NixFe100-x alloy thin films with varied Ni composition and deposition conditions using a vector network analyser (VNA) and coplanar waveguide [1][2][3][4]. The quality of the FMR response and the effective permeability in single layer films is particularly affected by the NiFe crystal structure, most notably over the fcc-bcc boundary at x=40, Figure 1. The FMR was also improved by proper choice of seed layer and lowering deposition pressure. Increasing substrate temperature was observed to have an actively detrimental effect on ferromagnetic resonance. The effect on FMR of modulating the composition in NiFe thin films was also studied using repeated bilayer structures with a constant total thickness of the form n[NixFe100-x/NiyFe100-y], where n is the number of bilayers and determines the period of modulation. Compared to single layers, the compositionally modulated structures were generally seen to enhance the FMR signal and increase the frequency of resonance, Figure 2.References: [1] Y. Ding et al. J. Appl. Phys. 96, 2969 (2004) [2] C. Kittel, Phys Rev 73, 2 (1948) [3] Y.V. Khivintsev. J. Appl. Phys. 108, 023907 (2010) [4] Kalarickal et al. J. Appl. Phys. 99, 093909 (2006)

A Systematic Ferromagnetic Resonance Study of Deposition Conditions in NiFe Thin Films for Shielding Applications.

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Presentations

Towards Optimised Tunable NiFe Multilayers for High Frequency Applications

Ferromagnetic Resonance of Tuneable Low Magnetostrictive NixFe100-x Superlattice Structures for High Frequency Application

Control of Static and Dynamic Magnetic Properties of NixFe100-x Alloy Thin Films

A Systematic Ferromagnetic Resonance Study of Deposition Conditions in NiFe Thin Films for Shielding Applications.

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