Fabrication and high-resolution electron microscopy study of FePt L1₀ /A1 graded exchange spring media

Abstract

We have prepared FePt L1 0 /A1 exchange spring graded media by controlling deposition temperature. The performance of the media was determined by the deposition conditions, particularly the cooling rate. By varying the deposition conditions a coercivity of 4.0 kOe was achieved without loss in remanent magnetization, the value corresponds to 88% reduction compared with that of FePt L1 0 single phase (32.2 kOe). High-resolution transmission electron microscopy (HRTEM) investigations have revealed that this drastic coercivity reduction originates from the unique microstructure of the specimens: coexistence of the L1 0 and A1 phases at the interphase boundary. In this region the two phases are dispersed one into another like inclusions in a matrix. Finally, the role of the complicated phase boundary on switching field reduction was discussed using micromagnetic simulations.

Substantial reduction in coercivity of perpendicular CoPt/FePt graded films with near-atomic flatness on glass substrates

“…This may be responsible for spontaneous demagnetization of hysteresis loop, although a further reduction of H c (2.0 kOe) is still observed. The sequential reduction of H c with increasing t CoPt suggested that the thicker soft layers may reduce the nucleation field of the soft layer, consistent with experimental and simulated results [6,8,[12][13][14][15][16]. The in-plane hysteresis loops indicates that the graded films with t CoPt 6 20 nm exhibit perpendicular anisotropies.…”

“…Most of them are focused on the reduction of coercivity in conventional continuous granular structure, e.g., FePt-C [9] and FePt-TiO 2 [10], or discontinues film on single-crystal MgO or glass substrate, e.g., Fe/ FePt [11] and FePt(A1)/FePt(L1 0 ) [12][13][14]. However, the conventional granular and discontinuous film structure is not appropriate for application of BPM.…”

Uncorrelated magnetic domains in decoupled SrFe12O19/Co hard/soft bilayers

“…Based on these results and the existing literature [19], it is concluded that in order to successfully fabricate a hard-soft composite where magnetization is enhanced at low coercivity penalty, a low degree of exchange-coupling is desirable since it may be sufficient to align the soft spins with the hard phase without facilitating massive domain wall propagation. In that sense, the composite bilayers presented here, and associated systems with low degrees of coupling, present the advantage of a larger coercivity when compared to fully exchange-coupled systems [16,17,44,45]. However, a complete absence of coupling must be avoided, as it leads to no soft spin alignment and therefore no increase in remanence.…”

“…However, a robust exchange-coupling between hard and soft phases has been reported to lead to a quite drastic decrease in coercivity as well [15][16][17][18][19][20], as a consequence of the fast propagation of unpinned domain walls generated at the soft phase. This has been debated as a reason for some of the disappointing results obtained in the development of novel hybrid permanent magnets [19][20][21][22][23].…”

Пленка сплава Pd-Fe с большим градиентом магнитной примеси: структурные и магнитные свойства

“…Мы полагаем, что для нашей пленки эффективная толщина слоя L1 0 -фазы увеличена за счет лежащих ниже слоев. Аналогичный эффект наблюдали в работе [18], где были совмещены эпитаксиальные слои PtFe со структурами A1 и L1 0 .…”