Orbital chirality and Rashba interaction in magnetic bands

The phenomenon of Rashba spin-orbit coupling is examined theoretically for an ultrathin magnetic layer in contact with a nonmagnetic heavy-metal layer. From a first-principles calculation, a large Rashba parameter of order 1 eV {} is obtained, which makes the Rashba interaction a powerful tool for enhancing the spin-transfer torque. Interestingly, the magnitude and sign of the parameter vary from energy band to energy band, which we attribute to band-specific chiral ordering of the orbital angular momentum. We argue that the band dependence of the Rashba parameter provides a natural explanation for a host of recent experiments and may enhance the potential for device application of the Rashba-active magnetic layer.