Exchange coupling in hard/soft-magnetic multilayer films with non-magnetic spacer layers

Abstract

The exchange coupling in textured HM/NM/α-Fe/NM/HM multilayer films (HM = NdFeB or PrFeB hard magnetic layers; NM = nonmagnetic Mo, Cu, and Cr layer) is shown to be indirect and long-range. The influences of thickness of NM spacer layer and HM layer, the material of HM phase and NM spacer layers, and the texture of HM layer, on the effective critical correlation length (Lexeff) and exchange-coupling between soft-magnetic (SM) and HM layers are investigated. A non-linear dependence of Lexeff on the thickness of NM spacer layer is observed. Magnetostatic interaction may lead to the observed non-linear dependence.

Anisotropic nanocomposite soft/hard multilayer magnets

“…So, in the following part, some factors that influence the exchange-coupling are discussed. [20] As can be seen in Fig. 1, it is clear that L eff ex shows an anisotropic behavior in textured multilayer films.…”

“…1(a) shows an XRD pattern typical of a textured HM/NM/Fe/NM/HM multilayer film. [20] In order to identify whether such nonlinear dependence is spacer-layer dependent, Cu and Cr spacer layers were used.…”

“…5, it is proposed that there is at least the existence of magnetostatic interactions between soft-and hard-magnetic layers, which leads to the observed non-linear dependence. [20] Later, Cui et al [22] realized anisotropic hard/soft multilayer films [Nd-Fe-B (30 nm)/Nd (3 nm)/Ta (1 nm)/Fe 67 Co 33 (10 nm)/Ta (1 nm)] N /Nd-Fe-B (30 nm)/Nd (3 nm) multilayer films (N = 0, 4, 9, 14,19) the Nd-Fe-B and Nd layers were each deposited at 600 • C. After the substrates were cooled down, the Ta (1 nm)/Fe 67 Co 33 (10 nm)/Ta (1 nm) layers were deposited at around 200 • C. After depositing a stack of the Nd-Fe-B (30 nm)/Nd (3 nm)/Ta (1 nm)/Fe 67 Co 33 (10 nm)/Ta (1 nm) layers, the substrate temperature was increased to 600 • C before depositing the next stack. After depositing all of these stacks, the thin films were annealed at 650 • C to allow Nd to diffuse into the Nd-Fe-B layer along the grain boundaries.…”

“…(color online) Variation of δ m(H) as the function of applied field for the thin film Mo (50 nm)/NdFeB (800 nm)/Cu (6 nm)/Fe (22 nm)/Cu (6 nm)/NdFeB (800 nm)/Mo (50 nm) (dark) and Mo (50 nm)/NdFeB (800 nm)/Cr (6 nm)/Fe (21 nm)/Cr (6 nm)/NdFeB (800 nm)/Mo (50 nm) (red) measured along the direction perpendicular to the film plane. [20] [22] All the films show strong perpendicular anisotropy because of the preferred orientation of (001) planes parallel to the films. The remanent magnetization µ 0 M r and maximum energy product (BH) max are shown in Fig.…”

Magnetic hardening of Nd-Ce-Fe-B films with high Ce concentration

“…The formation of boundary phase between adjacent grains has been observed from the TEM image. The boundary phase has been expected to cause a reduction in intergranular exchange coupling, which plays an important role in improving the coercivity 17 , 30 . The reduced intergranular exchange coupling is examined by the observation of magnetic domain structure with MFM (Fig.…”