Biased magnetic materials in RAM applications

Författare

Jörgen Ramprecht
Daniel Sjöberg

Summary, in English

The magnetization of a ferro- or ferri-magnetic material has been

modeled with the Landau-Lifshitz-Gilbert (LLG) equation. In this

model demagnetization effects are included. By applying a linearized

small signal model of the LLG equation, it was found that the

material can be described by an effective permeability and with the

aid of a static external biasing field, the material can be switched

between a Lorentz-like material and a material that exhibits a

magnetic conductivity. Furthermore, the reflection coefficient for

normally impinging waves on a PEC covered with a

ferro/ferri-magnetic material, biased in the normal direction, is

calculated. When the material is switched into the resonance mode,

we found that there will be two distinct resonance frequencies in

the reflection coefficient, one associated with the precession

frequency of the magnetization and one associated with the thickness

of the layer. The former of these resonance frequencies can be

controlled by the bias field and for a bias field strength close to

the saturation magnetization, where the material starts to exhibit a

magnetic conductivity, one can achieve low reflection (around -20

dB) for a quite large bandwidth (more than two decades).

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