High-frequency characterization of Permalloy nanosized strips using network analyzer ferromagnetic resonance

• Published in: Journal of applied physics 2008-04, Vol.103 (7), p.07C508-07C508-3
• Main Authors: Kuanr, Bijoy K., Lopusnik, Radek, Malkinski, Leszek M., Wenger, Matt, Yu, Minghui, Scherer, Donald, Camley, R. E., Celinski, Z.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.2839625

We report on the dynamic properties of Permalloy nanostrips at gagahertz frequencies. The thickness of the strips is 100 nm , strip width is 300 nm , strip spacing is 1 μ m , and length is 0.3 - 100 μ m ; aspect ratios are 1:1, 1:2, 1:3, 1:5, 1:10, and 1:333. The dynamic behavior was studied by network analyzer ferromagnetic resonance (FMR) using Permalloy strips on a coplanar waveguide in flip-chip geometry. The FMR mode frequencies ( f r ) can be controlled by the aspect ratio as well as by the applied magnetic field ( H ) . In longer strips (1:10 and 1:333), the excitation frequencies show a soft mode behavior ( H eff = 990 Oe ) when the field is along the hard axis. However, along the easy axis (along the strip length), f r increases with applied field. At a field of 3 kOe , f r values are almost independent of aspect ratio along the easy axis except for the 1:1 strip. Along the hard axis, the frequencies are strongly dependent upon the aspect ratio. We also observed that the frequency linewidths of the strips are dependent on the aspect ratio.