IS HUND 2ND RULE RESPONSIBLE FOR THE ORBITAL MAGNETISM IN SOLIDS

We argue that the key parameter responsible for the exchange-correlati on enhancement of the orbital magnetic moments in solids is ''Hubbard U'' rather than the intra-atomic Hund's second rule coupling, being co nsistent with a more general concept of the orbital polarization. This leads us to a unified rotationally invariant local density approximat ion (LDA) + U prescription for the orbital magnetism. Validity of the present theory is demonstrated by numerical calculations, which perfec tly account for the orbital magnetism as well as the canted magnetic s tructure in CoO.