HELIMAGNETIC STRUCTURES IN EPITAXIAL ND Y SUPERLATTICES AND ALLOYS/

The complex magnetic structure of Nd exhibits a new magnetic phase whe n grown epitaxially, either as a stabilized double hexagonal close-pac ked alloy, or as part of a Nd/Y superlattice. In tile alloy and in tho se superlattices with small Nd/Y ratios, the incommensurate b axis mod ulated structure exhibited by elemental Nd at T-N = 19.9 K is absent, In its place, incommensurate helimagnetic order, similar to that in di lute yttrium alloys of the heavy lanthanides, appears below approximat ely 30 K. Evidence for coherent propagation of the magnetic spiral thr ough the Y spacers is observed in some Y-rich superlattices. As the Nd :Y ratio in the superlattices is increased, the b axis modulated phase s reappear and coexist with the helical phase. Thick epitaxial Nd film s, nevertheless, exhibit only bulklike magnetic structure. We discuss these observations in terms of band structure modifications.