SPIN-ORBIT-INDUCED MAGNETIC-ANISOTROPY FOR IMPURITIES IN METALLIC SAMPLES - I - SURFACE ANISOTROPY

Motivated by recent measurements of Kondo resistivity in thin films an d wires, where the Kondo amplitude is suppressed for thinner samples, the surface anisotropy for magnetic impurities is studied. That anisot ropy is developed in those cases where, in addition to the exchange in teraction with the impurity, there is strong spin-orbit interaction fo r conduction electrons around the impurity in the ballistic region. Th e asymmetry in the neighborhood of the magnetic impurity exhibits the anisotropy axis n which, in the case of a plane surface, is perpendicu lar to the surface. The anisotropy energy is Delta E=K-d(nS)(2) for sp in S, and the anisotropy constant K-d is inversionally proportional to distance d measured from the surface and K-d>0 Thus at low temperatur e the spin is frozen in a singlet or doubler of lowest energy. The inf luence of that anisotropy on the electrical resistivity is the subject of the following paper (II).