Observations of exchange coupling in Nd2Fe14B/Fe/Nd2Fe14B sandwich structures and their magnetic properties

Sandwich structures of Nd2Fe14B/Fe/Nd2Fe14B magnetic films have been grown by a KrF excimer laser (lambda = 248 nm) ablation technique. Magnetic properties were characterized by varying the thickness of hard (Nd2Fe14B) and soft (Fe) magnetic films and the volume fraction as well. In the (x) nm [NdFeB]/(y) nm [Fe]/(x) nm [NdFeB]/(1 0 0)Si structure the thickness (x) was varied from 3.6 to 54 nm, and (y) from 15 to 112 nm. At (y) = 15-20 nm where the volume fraction of Fe corresponded to 61-75%, the sandwich structure exhibited an enhanced M-r/M-s and H-i(c) as well from the result of the exchange coupling between the magnetic layers. Experimentally calculated exchange constant (A(s)) of A(s) = 2.5 x 10(-10) J/m was estimated using the intrinsic coercivity (H-i(c)) of 1.2 kOe at 5 K for the sandwich magnetic trilayers. (C) 1999 Elsevier Science B.V. All rights reserved.