SPIN ANHARMONICITY AND ZERO-POINT FLUCTUATIONS IN WEAK ITINERANT-ELECTRON MAGNETS

It is shown that the conventional spin fluctuation (SF) theory of weak intinerant magnets does not take into account the effects of strong spin anharmonicity caused by large zero-point SF amplitudes and, therefore, may break down in anharmonic magnets. A microscopic approach based on a quasiparticle Fermi liquid description of strongly anharmonic weak intinerant magnets is presented generalizing the conventional theory to account for both thermal and zero-point SF.