A single mechanism for slow domain wall motion in both ferroelectrics and ferromagnets

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Abstract
A tunneling theory of slow wall motion in ferromagnets is applied to BaTiO3 using the data of Miller and Savage. It is shown that, over seven decades of velocity for which the approximations are valid and for which data are available, the theory fits the data well and even gives the appreciable change of slope in the lnu -versus-l/E plot found experimentally. A material will or will not behave as though it had a true coercive force, below which wall motion does not occur, depending on whether a quantity called Z* is large or small, respectively. Z* is the average range of pinning centers in the crystal, normalized to the (approximate) tunneling length. For BaTiO3 it was determined that Z*=6; u0, a characteristic tunneling velocity, was 2.72 cm/s; Ec, the classical coercive field, was 763 V/cm. It is concluded that domain wall motion in ferromagnets and ferroelectrics proceeds by the same mechanism.