Shock-Induced Demagnetization of YIG

Measurements have been made of the shock‐induced reduction in the component of the magnetization of polycrystalline $\mathrm{YIG}$ along the direction of an applied field. This reduction is induced by the passage of an explosively generated shock wave in a direction perpendicular to the applied field. The data indicate that the passage of the shock wave through the sample induces a uniaxial magnetic anisotropy in the material. This magnetic anisotropy arises from the stress anisotropy associated with the shock‐wave compression of a material having a nonzero yield strength. The induced magnetic anisotropy makes the shock‐propagation direction an easy direction of magnetization, and the observed reduction in the component of the magnetization along the applied field arises mainly from the rotation of the magnetization toward the easy direction. Experiments were performed at three bias fields, each at three widely spaced shock pressures. At 0.09 Mbar, the induced anisotropy energy may be described by a term in ${\sin }^2\theta$ . The coefficient of this term is in agreement with the value estimated from the usual magnetoelastic coefficients. At 0.20 and 0.44 Mbar, the contribution from a term in ${\sin }^4\theta$ is observed to dominate that from the ${\sin }^2\theta$ term, and the coefficient of the ${\sin }^4\theta$ term increases several‐fold over its low‐pressure value. A possible origin of this increase is discussed.