The Saturation Magnetostriction Constants of Nickel within the Temperature Range - 196  to 365 C

The spontaneous magnetostriction of cubic crystals can be expressed in the form λ = C 0 + C 1 (α 1 2 β 1 2 + α 2 2 β 2 2 + α 3 2 β 3 2 ) + C 2 (α 1 α 2 β 1 β 2 + α 2 α 3 β 2 β 3 + α 3 α 1 β 3 β 1 ) where the α 1 and β 1 are, respectively, the direction cosines of the magnetization vector and the measuring direction, with respect to the crystal axes. The coefficients C 1 and C 2 have been determined for nickel within the temperature range - 196°C to the Curie point (365°C) using calibrated strain gauges. At -196°C, C 1 = -85.0 × 10 -6 and C 2 = -85.4 × 10 -6 . Both constants increase monotonically to zero at 365°C. The room temperature (20°C) values are C 1 = -77.2 × 10 -6 and C 2 = -70.0 × 10 -6 . For a polycrystal the spontaneous magnetostriction may be expressed in the form λ = C + fraction three-twosλ s cos 2 x where x is the angle between α and β. Measurements of λ s have been made in the same way and they are in good agreement with the values calculated assuming uniform stress, namely λ s =fraction four-fifteenths C 1 + fraction one-fifth C 2 .