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Large spin Hall magnetoresistance and its correlation to the spin-orbit torque in W/CoFeB/MgO structures.

Cho S, Baek SH, Lee KD, Jo Y, Park BG - Sci Rep (2015)

Bottom Line: This implies the existence of an inverse effect, in which the conductivity in such structures should depend on the magnetization orientation.We observe that the MR is independent of the angle between the magnetization and current direction but is determined by the relative magnetization orientation with respect to the spin direction accumulated by the spin Hall effect, for which the symmetry is identical to that of so-called the spin Hall magnetoresistance.The MR of ~1% in W/CoFeB/MgO samples is considerably larger than those in other structures of Ta/CoFeB/MgO or Pt/Co/AlOx, which indicates a larger spin Hall angle of W.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, KAIST, Daejeon 305-701, Korea.

ABSTRACT
The phenomena based on spin-orbit interaction in heavy metal/ferromagnet/oxide structures have been investigated extensively due to their applicability to the manipulation of the magnetization direction via the in-plane current. This implies the existence of an inverse effect, in which the conductivity in such structures should depend on the magnetization orientation. In this work, we report a systematic study of the magnetoresistance (MR) of W/CoFeB/MgO structures and its correlation with the current-induced torque to the magnetization. We observe that the MR is independent of the angle between the magnetization and current direction but is determined by the relative magnetization orientation with respect to the spin direction accumulated by the spin Hall effect, for which the symmetry is identical to that of so-called the spin Hall magnetoresistance. The MR of ~1% in W/CoFeB/MgO samples is considerably larger than those in other structures of Ta/CoFeB/MgO or Pt/Co/AlOx, which indicates a larger spin Hall angle of W. Moreover, the similar W thickness dependence of the MR and the current-induced magnetization switching efficiency demonstrates that MR in a non-magnet/ferromagnet structure can be utilized to understand other closely correlated spin-orbit coupling effects such as the inverse spin Hall effect or the spin-orbit spin transfer torques.

No MeSH data available.


Related in: MedlinePlus

Dependence of the magnetoresistance on the CoFeB thickness.The MR for the sample W(5 nm)/CoFeB(t)/MgO(1.6 nm), where t varies from 0.8 to 1.4 nm using field sweep (a) and rotating (b) measurement. (c) Rxx vs Hy curves for the samples W(5 nm)/CoFeB(3 nm) and CoFeB(3 nm). Both samples show the in-plane magnetic anisotropy.
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f4: Dependence of the magnetoresistance on the CoFeB thickness.The MR for the sample W(5 nm)/CoFeB(t)/MgO(1.6 nm), where t varies from 0.8 to 1.4 nm using field sweep (a) and rotating (b) measurement. (c) Rxx vs Hy curves for the samples W(5 nm)/CoFeB(3 nm) and CoFeB(3 nm). Both samples show the in-plane magnetic anisotropy.

Mentions: For a better understanding of the SMR of W/CoFeB/MgO samples, we investigate the dependence of SMR on the thicknesses of the W and CoFeB layers. We initially examine the effect of the CoFeB thickness on SMR. Figure 4(a) shows Rxx as a function of a transverse field, Hy for samples with different CoFeB thicknesses ranging from 0.8 to 1.4 nm, in which perpendicular magnetic anisotropy can persist. We find that Rxx normalized by the resistance at Hy = 1.5 T (R0) does not vary much with the CoFeB thickness. The similar angular dependence levels of these four samples, as shown in Fig. 4(b), confirms that Rxx does not significantly rely on the CoFeB thickness. To verify the role of the W layer, we compare samples of thicker CoFeB (3.0 nm) with and without a W layer, both of which showing in-plane magnetic anisotropy. Figure 4(c) shows Rxx as a function of Hy. We note that the magnetization of both samples is aligned in the x-direction without a magnetic field due to the shape anisotropy of the Hall bar structure. The MR is considerably larger for the sample with W underlayer. The results shown in Fig. 4 clearly demonstrate that the W layer plays a key role in the observed SMR.


Large spin Hall magnetoresistance and its correlation to the spin-orbit torque in W/CoFeB/MgO structures.

Cho S, Baek SH, Lee KD, Jo Y, Park BG - Sci Rep (2015)

Dependence of the magnetoresistance on the CoFeB thickness.The MR for the sample W(5 nm)/CoFeB(t)/MgO(1.6 nm), where t varies from 0.8 to 1.4 nm using field sweep (a) and rotating (b) measurement. (c) Rxx vs Hy curves for the samples W(5 nm)/CoFeB(3 nm) and CoFeB(3 nm). Both samples show the in-plane magnetic anisotropy.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4589767&req=5

f4: Dependence of the magnetoresistance on the CoFeB thickness.The MR for the sample W(5 nm)/CoFeB(t)/MgO(1.6 nm), where t varies from 0.8 to 1.4 nm using field sweep (a) and rotating (b) measurement. (c) Rxx vs Hy curves for the samples W(5 nm)/CoFeB(3 nm) and CoFeB(3 nm). Both samples show the in-plane magnetic anisotropy.
Mentions: For a better understanding of the SMR of W/CoFeB/MgO samples, we investigate the dependence of SMR on the thicknesses of the W and CoFeB layers. We initially examine the effect of the CoFeB thickness on SMR. Figure 4(a) shows Rxx as a function of a transverse field, Hy for samples with different CoFeB thicknesses ranging from 0.8 to 1.4 nm, in which perpendicular magnetic anisotropy can persist. We find that Rxx normalized by the resistance at Hy = 1.5 T (R0) does not vary much with the CoFeB thickness. The similar angular dependence levels of these four samples, as shown in Fig. 4(b), confirms that Rxx does not significantly rely on the CoFeB thickness. To verify the role of the W layer, we compare samples of thicker CoFeB (3.0 nm) with and without a W layer, both of which showing in-plane magnetic anisotropy. Figure 4(c) shows Rxx as a function of Hy. We note that the magnetization of both samples is aligned in the x-direction without a magnetic field due to the shape anisotropy of the Hall bar structure. The MR is considerably larger for the sample with W underlayer. The results shown in Fig. 4 clearly demonstrate that the W layer plays a key role in the observed SMR.

Bottom Line: This implies the existence of an inverse effect, in which the conductivity in such structures should depend on the magnetization orientation.We observe that the MR is independent of the angle between the magnetization and current direction but is determined by the relative magnetization orientation with respect to the spin direction accumulated by the spin Hall effect, for which the symmetry is identical to that of so-called the spin Hall magnetoresistance.The MR of ~1% in W/CoFeB/MgO samples is considerably larger than those in other structures of Ta/CoFeB/MgO or Pt/Co/AlOx, which indicates a larger spin Hall angle of W.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, KAIST, Daejeon 305-701, Korea.

ABSTRACT
The phenomena based on spin-orbit interaction in heavy metal/ferromagnet/oxide structures have been investigated extensively due to their applicability to the manipulation of the magnetization direction via the in-plane current. This implies the existence of an inverse effect, in which the conductivity in such structures should depend on the magnetization orientation. In this work, we report a systematic study of the magnetoresistance (MR) of W/CoFeB/MgO structures and its correlation with the current-induced torque to the magnetization. We observe that the MR is independent of the angle between the magnetization and current direction but is determined by the relative magnetization orientation with respect to the spin direction accumulated by the spin Hall effect, for which the symmetry is identical to that of so-called the spin Hall magnetoresistance. The MR of ~1% in W/CoFeB/MgO samples is considerably larger than those in other structures of Ta/CoFeB/MgO or Pt/Co/AlOx, which indicates a larger spin Hall angle of W. Moreover, the similar W thickness dependence of the MR and the current-induced magnetization switching efficiency demonstrates that MR in a non-magnet/ferromagnet structure can be utilized to understand other closely correlated spin-orbit coupling effects such as the inverse spin Hall effect or the spin-orbit spin transfer torques.

No MeSH data available.


Related in: MedlinePlus