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    Spin-transfer torque in disordered weak ferromagnets

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    We study theoretically the spin transfer effect on a domain wall in disordered weak ferromagnets. We have identified the adiabatic condition for the disordered case as \lambda \gg \lambda_{\rm D}\equiv \sqrt{{\hbar D}/{\spol}}, where DD and \spol are the diffusion constant and the spin splitting energy due to the ss-dd type exchange interaction, respectively, and found out that perfect spin-transfer effect occurs even in weak ferromagnets as long as this condition is satisfied. The effective β\beta term arising from the force turns out to govern the wall dynamics, and therefore, the wall motion can be as efficient as in strong ferromagnets even if \spol is small