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

Abstract

Abstract. Effect of Rh spacer on synthetic antiferromagnetic (SAF) coupling was investigated in subnano-crystalline (Fe 65 Co 35 ) 88 B 12 (30 nm)/ Rh/ (Fe 65 Co 35 ) 88 B 12 (30 nm) films. The flopping field (H f ) showed oscillatory behavior with respect to Rh thickness, d Rh . The 1st peak of H f appeared at d Rh = 0.9 nm, and the 2nd at d Rh = 1.7 nm. These results are analyzed in terms of interlayer coupling effect including the bilinear (J 1 ) and biquadratic (J 2 ) coupling energy, and found to be 0.65 erg/cm 2 for J 1 and 0.12 erg/cm 2 for J 2 at the 1st peak. Compared to SAF coupling with Ru spacer, the 1st peak thickness with Rh spacer is thicker. This is because the effective spacer layer thickness decreases by the polarization of Rh neighboring FeCo based material. IntroductionFor high density perpendicular recording media, a thick soft magnetic underlayer (SUL) is required for the magnetic flux path for writing. 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 [1-3] 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]. In this paper, we investigate interlayer coupling by using Rh as a spacer material to obtain the material guide of spacer for further enhancement of H f .

Microwave Oscillator Based on a Single Straintronic Magnetotunneling Junction

“…We solve Equation (8) numerically to find the magnetization component We assumed that the soft layer of the MTJ is made of Terfenol-D and used the material and device parameters in Table I. The hard layer (fashioned out of a synthetic antiferromagnet, such as FeCoB with Rh spacer layers [13]) has the same geometry as the soft layer. The adhesion layer at the bottom of the MTJ stack is assumed to be thin enough to not impede strain transfer from the underlying piezoelectric into the soft layer.…”

Ru thickness-dependent interlayer coupling and ultrahigh FMR frequency in FeCoB/Ru/FeCoB sandwich trilayers

“…[1] The IEC was widely used in magnetic devices, [2,3] such as magnetic recording devices, giant magnetoresistance effect, tunneling magnetoresistance effect, [4][5][6][7][8] etc. The materials currently used to study IEC are mainly composed of Fe, [9][10][11] Co, [12] FeCo, [13] NiFe, [14][15][16][17] and FeCo alloys, [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] separated by non-ferromagnetic materials, such as Cu, [14,35] Cr, [9,36] and Ru. [3,[15][16][17][18][24][25][26]37] For the FM/NM/FM structure, the coupling strength and type of IEC are mainly related to the material compositions and the thickness value of FM layer and NM layer.…”