Magnetostriction of Commercial Ferrite Memory Cores

The polycrystalline saturation magnetostriction λs and volume magnetostriction δω/δH of some thirty types of commercial ferrite memory cores have been measured. A capacitance technique sufficiently sensitive to measure elongations of ∼0.1 Å and Δl/l of ∼3×10−8 was employed, and λs was determined by rotation of the saturated moment through 90°, λs values between −1×10−7 to −1×10−5 and λω/λH values from −1×10−10 to −7×10−10 Oe−1 were obtained. Since these magnetostriction constants measure coupling of magnetization and dimensional parameters, the data reflects a wide range of core sensitivity to stress-induced demagnetization and ``magnetostrictive ringing'' of cores upon switching.