Tensor nature of permeability and its effects in inductive magnetic devices

The tensor nature of the permeability of soft magnetic materials with an in-plane anisotropy was investigated. Using tensor transformation, the measured permeability was proportional to cos(2) alpha, where a is the angle between the external exciting magnetic field and hard axis of magnetic material, which was proven by experimental data for thin-film materials CoFeHfO and CoTaZrTb. A new type of inductor was designed and simulated by Ansoft Maxwell 3-D to study the effects of the tensor nature of the permeability in the simulation of inductors. It is important to appropriately account for the tensor nature of the permeability of soft magnetic materials in inductive device simulation to establish realistic device models. A magnetic integrated inductor with extremely low DC resistance (< 9 m Omega) was fabricated. Its high-frequency performance was measured and compared to HFSS simulation using appropriate tensor permeability.