Anomalous Shock-Induced Demagnetization of Nickel Ferrite

• Published in: Journal of applied physics 1966-01, Vol.37 (11), p.4066-4070
• Main Author: Royce, E. B.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.1707977

Measurements of the demagnetization of nickel ferrite under explosively generated shock conditions have been made. Samples were biased close to saturation by a permanent magnet. The shock-induced reduction in magnetic flux through the sample was detected by pickup coils wound on the ferrite cores which completed the magnetic circuit between the sample and biasing magnet. The experiments show an apparent complete destruction of the spontaneous magnetization of the material at all shock pressures between 43 and 430 kbar. The susceptibility of the shocked material, however, is found to be an order of magnitude larger than the calculated paramagnetic susceptibility. The effect of shock pressure on the Néel temperature combined with the effect of shock heating would lead to total demagnetization only at shock pressures well above 400 kbar. The most plausible mechanism for the observed anomalous demagnetization is shown to be a shock-induced magnetic anisotropy, arising from the anisotropic microscopic strain associated with the shock. Equation-of-state data needed for the interpretation of the magnetic work are also presented.