EFFICIENT PREISACH DEMAGNETIZATION ALGORITHM AND ITS EXPERIMENTAL TESTING

The topic of demagnetization has always been considered important to t he area of magnetics in general. Whether it is required to characteriz e the initial permeability of a premagnetized sample or to erase, nond estructively, previously recorded data on disks or tapes, demagnetizat ion processes are indispensable. Theoretically, demagnetization can be achieved by applying infinite ac field cycles with slowly decaying am plitudes. In practice, however, only a finite subset of this sequence may be applied. As a result, achieving the demagnetized state, or even a zero residual magnetization state, becomes uncertain. The purpose o f this paper is to present an efficient Preisach-type demagnetization algorithm that can lead to a zero residual magnetization state within few field cycles. While this state might not fully match the demagneti zed state, it can be regarded as a good approximation especially for d ata erasure applications. The algorithm has been experimentally tested and compared to particular demagnetization techniques employing finit e ac field cycles with decaying amplitudes. Some sample results of thi s experimental testing are reported in the paper.