Material Problems in Soft-Magnetic Underlayers with High Stray-Field Stability Using Interlayer Magnetic Coupling.

Effect of Rh spacer on Synthetic-Antiferromagnetic Coupling in FeCoB/Rh/FeCoB Films

“…Note that in this equation, domain structure and dispersion of magnetic anisotropy are not considered. The net magnetization of the two SM layers is calculated by the equilibrium angle of  1 and  2 , which were determined from the minimum energy condition of equation (1). Then MH loop is derived using following equation;…”

“…The thick SUL introduces spike noise and wide adjacent track erasure (WATE). To avoid these problems, the SUL with synthetic antiferromagnetic (SAF) coupled structure have been widely used [1][2][3] as following reasons [4]; 1) Néel walls are formed in the top and bottom soft magnetic (SM) layers in a pair [5], which is effective for suppression of spike noise, and 2) Low susceptibility are realized when the angle of applied field is slightly tilted from the film normal, which can efficiently restrain WATE. We have already reported that large flopping field (H f ) appeared for (Fe 65 Co 35 ) 88 B 12 (30nm)/ Ru/ (Fe 65 Co 35 ) 88 B 12 (30 nm) stacked SUL at the 1st peak with Ru spacer thickness (d Ru ) of 0.3 nm due to the extremely large unidirectional interlayer coupling energy J 1 of 1.9 erg/cm 2 as a result of composition dependence of SM materials [6][7].…”

Magnetization reversal mechanism of soft magnetic underlayer pinned by antiferromagnetic layer

“…of this technique is to realize a high exchange coupling field, H ex , for maintaining the singledomain structure under a high stray field. However, H ex considerably decreases with increase in the SUL thickness beyond theoretical expectation on the assumption of a constant unidirectional magnetic anisotropy [4,5]. In this paper, in order to clarify the mechanism of the degradation of H ex in a thick SUL pinned by an AFM layer, local spin reversal along the film depth is discussed based on investigation of the domain structure and hysteresis loop.…”

“…However, in a media with such a thick SUL, suppression of spike noise caused by leakage flux from a 1801-domain wall is a serious problem. It is well known that realization of a single-domain structure without a 1801-domain wall in the whole disk can be performed by an exchange coupled SUL with an antiferromagnetic (AFM) layer [1][2][3][4]. of this technique is to realize a high exchange coupling field, H ex , for maintaining the singledomain structure under a high stray field.…”

Microstructure of CoNiFeB electroless-deposited soft magnetic underlayer for perpendicular recording media

“…Amorphous CoZrNb [2] and nanocrystalline FeTaC films [3] are SULs which are deposited on glass substrates by the sputtering method. These SULs are separated by a thin intermediate nonmagnetic layer to eliminate the spike noise by the antiferromagnetic coupling of the two soft magnetic layers [4]. However, since these SULs cannot be fabricated by the electroless-deposition method, a different type of SUL is under investigation for future industrial applications.…”