Effect of Tensile Stress on the Domain-Nucleation Field of Iron Whiskers

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Abstract
For an infinitely long iron rod of rectangular cross section with a [100] axis, and which has been magnetized in the [100] direction, theory predicts that an opposing field of about 565 Oe is required to reverse the direction of its magnetization, and that this reversing field increases linearly with axial stress. The proportionality constant relating the reversing field (nucleation field) to the stress is 3λ100/Ms, where λ100 is the saturation magnetostriction constant in the [100] direction and Ms is the saturation magnetization. Iron whiskers may be grown with a rectangular cross section and with the axis in the [100] direction. DeBlois and Bean studied the nucleation field at zero tension in such whiskers and found that in some parts of some whiskers the nucleation field approached the theoretical value. For convenience we call these ``ideal'' parts of the whiskers. We have studied the relationship between nucleation field and stress for ideal parts of whiskers and have found the proportionality constant to be 2.94 ± 0.32 Oe/kg/mm2, in reasonable agreement with the value obtained using the literature values of λ100 and Ms.