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Modification of perpendicular magnetic anisotropy and domain wall velocity in Pt/Co/Pt by voltage-induced strain.

Shepley PM, Rushforth AW, Wang M, Burnell G, Moore TA - Sci Rep (2015)

Bottom Line: K(eff), measured by the extraordinary Hall effect, is reduced by 10 kJ/m(3) by tensile strain out-of-plane ε(z) = 9 × 10(-4), independently of the film thickness, indicating a dominant volume contribution to the magnetostriction.The same strain reduces the coercive field by 2-4 Oe, and increases the domain wall velocity measured by wide-field Kerr microscopy by 30-100%, with larger changes observed for thicker Co layers.We consider how strain-induced changes in the perpendicular magnetic anisotropy can modify the coercive field and domain wall velocity.

View Article: PubMed Central - PubMed

Affiliation: School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom.

ABSTRACT
The perpendicular magnetic anisotropy K(eff), magnetization reversal, and field-driven domain wall velocity in the creep regime are modified in Pt/Co(0.85-1.0 nm)/Pt thin films by strain applied via piezoelectric transducers. K(eff), measured by the extraordinary Hall effect, is reduced by 10 kJ/m(3) by tensile strain out-of-plane ε(z) = 9 × 10(-4), independently of the film thickness, indicating a dominant volume contribution to the magnetostriction. The same strain reduces the coercive field by 2-4 Oe, and increases the domain wall velocity measured by wide-field Kerr microscopy by 30-100%, with larger changes observed for thicker Co layers. We consider how strain-induced changes in the perpendicular magnetic anisotropy can modify the coercive field and domain wall velocity.

No MeSH data available.


Related in: MedlinePlus

(a) Domain wall velocity v plotted against applied field H and (b) natural logarithm of v plotted against H−1/4. Both plots show data for unstrained Pt/Co(t)/Pt (black open shapes) and Pt/Co(t)/Pt under tensile out-of-plane strain induced by applying 150 V to the piezoelectric transducers (red solid shapes), for t = 0.85 (circles), 0.95 (squares) and 1.0 nm (triangles). (c) Natural logarithm of v plotted against H−1/4 for Pt/Co(t)/Pt t = 1.0 nm with the transducer at voltages of -30, 0, 50, 100 and 150 V. The straight lines in b and c are fits of Equation 1 to the data.
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f3: (a) Domain wall velocity v plotted against applied field H and (b) natural logarithm of v plotted against H−1/4. Both plots show data for unstrained Pt/Co(t)/Pt (black open shapes) and Pt/Co(t)/Pt under tensile out-of-plane strain induced by applying 150 V to the piezoelectric transducers (red solid shapes), for t = 0.85 (circles), 0.95 (squares) and 1.0 nm (triangles). (c) Natural logarithm of v plotted against H−1/4 for Pt/Co(t)/Pt t = 1.0 nm with the transducer at voltages of -30, 0, 50, 100 and 150 V. The straight lines in b and c are fits of Equation 1 to the data.

Mentions: Finally, we investigate the changes in magnetization reversal further by studying domain wall creep motion. We measure this using the wide-field Kerr microscopy technique described under Methods. Figure 3a shows the domain wall velocity v plotted against the applied driving field H and Figure 3b shows the natural logarithm of v plotted against H−1/4 for Pt/Co/Pt with 0.85, 0.95 and 1.0 nm of Co, with the piezoelectric transducer at 0 V (unstrained) and 150 V (tensile strain). The linear behaviour of all datasets in Figure 3b and the fitting of Equation 1 is consistent with domain wall motion in the creep regime. Under tensile strain the velocity of the domain walls increases and we observe that the difference in domain wall velocity between 0 V and 150 V increases with applied field. Figure 4 shows the ratio of the domain wall velocity under tensile strain to the velocity in the unstrained state (0 V). For t = 1 nm Co we observe a strain induced increase in the domain wall velocity by a factor of 2 measured at a magnetic field of 108 Oe, corresponding to an unstrained domain wall velocity of 60 μm/s.


Modification of perpendicular magnetic anisotropy and domain wall velocity in Pt/Co/Pt by voltage-induced strain.

Shepley PM, Rushforth AW, Wang M, Burnell G, Moore TA - Sci Rep (2015)

(a) Domain wall velocity v plotted against applied field H and (b) natural logarithm of v plotted against H−1/4. Both plots show data for unstrained Pt/Co(t)/Pt (black open shapes) and Pt/Co(t)/Pt under tensile out-of-plane strain induced by applying 150 V to the piezoelectric transducers (red solid shapes), for t = 0.85 (circles), 0.95 (squares) and 1.0 nm (triangles). (c) Natural logarithm of v plotted against H−1/4 for Pt/Co(t)/Pt t = 1.0 nm with the transducer at voltages of -30, 0, 50, 100 and 150 V. The straight lines in b and c are fits of Equation 1 to the data.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4300497&req=5

f3: (a) Domain wall velocity v plotted against applied field H and (b) natural logarithm of v plotted against H−1/4. Both plots show data for unstrained Pt/Co(t)/Pt (black open shapes) and Pt/Co(t)/Pt under tensile out-of-plane strain induced by applying 150 V to the piezoelectric transducers (red solid shapes), for t = 0.85 (circles), 0.95 (squares) and 1.0 nm (triangles). (c) Natural logarithm of v plotted against H−1/4 for Pt/Co(t)/Pt t = 1.0 nm with the transducer at voltages of -30, 0, 50, 100 and 150 V. The straight lines in b and c are fits of Equation 1 to the data.
Mentions: Finally, we investigate the changes in magnetization reversal further by studying domain wall creep motion. We measure this using the wide-field Kerr microscopy technique described under Methods. Figure 3a shows the domain wall velocity v plotted against the applied driving field H and Figure 3b shows the natural logarithm of v plotted against H−1/4 for Pt/Co/Pt with 0.85, 0.95 and 1.0 nm of Co, with the piezoelectric transducer at 0 V (unstrained) and 150 V (tensile strain). The linear behaviour of all datasets in Figure 3b and the fitting of Equation 1 is consistent with domain wall motion in the creep regime. Under tensile strain the velocity of the domain walls increases and we observe that the difference in domain wall velocity between 0 V and 150 V increases with applied field. Figure 4 shows the ratio of the domain wall velocity under tensile strain to the velocity in the unstrained state (0 V). For t = 1 nm Co we observe a strain induced increase in the domain wall velocity by a factor of 2 measured at a magnetic field of 108 Oe, corresponding to an unstrained domain wall velocity of 60 μm/s.

Bottom Line: K(eff), measured by the extraordinary Hall effect, is reduced by 10 kJ/m(3) by tensile strain out-of-plane ε(z) = 9 × 10(-4), independently of the film thickness, indicating a dominant volume contribution to the magnetostriction.The same strain reduces the coercive field by 2-4 Oe, and increases the domain wall velocity measured by wide-field Kerr microscopy by 30-100%, with larger changes observed for thicker Co layers.We consider how strain-induced changes in the perpendicular magnetic anisotropy can modify the coercive field and domain wall velocity.

View Article: PubMed Central - PubMed

Affiliation: School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom.

ABSTRACT
The perpendicular magnetic anisotropy K(eff), magnetization reversal, and field-driven domain wall velocity in the creep regime are modified in Pt/Co(0.85-1.0 nm)/Pt thin films by strain applied via piezoelectric transducers. K(eff), measured by the extraordinary Hall effect, is reduced by 10 kJ/m(3) by tensile strain out-of-plane ε(z) = 9 × 10(-4), independently of the film thickness, indicating a dominant volume contribution to the magnetostriction. The same strain reduces the coercive field by 2-4 Oe, and increases the domain wall velocity measured by wide-field Kerr microscopy by 30-100%, with larger changes observed for thicker Co layers. We consider how strain-induced changes in the perpendicular magnetic anisotropy can modify the coercive field and domain wall velocity.

No MeSH data available.


Related in: MedlinePlus