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

Abstract

The perpendicular magnetic anisotropy Keff, 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. Keff, measured by the extraordinary Hall effect, is reduced by 10 kJ/m3 by tensile strain out-of-plane εz = 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.

Universal domain wall dynamics under electric field in Ta/CoFeB/MgO devices with perpendicular anisotropy

“…4d. Although a dependence of U C on anisotropy is expected in the creep theory1011, this feature is consistent with recent results of modulation of anisotropy in Pt/Co/Pt32 and Ta/CoFeB/MgO33 films. Between these two regimes for 8 mT< μ 0 H <12 mT, an intermediate depinning regime occurs, which corresponds to the tails of the creep regime20 where the energy barriers vanish linearly as Δ E ∼( H / H dep −1) approaching H dep .…”

Strong reduction of the coercivity by a surface acoustic wave in an out-of-plane magnetized epilayer

“…The impact of the SAW on DW propagation can probably not be fully neglected in the analysis. It would act through the transient increase of the DW width ∝ 1/ √ K u (ε SAW ), similar to the observations of Shepley et al [35] under static strain variations. The probabilistic calculation of SAWassisted nucleation-propagation reversal is beyond the scope of this Rapid Communication, but could, for instance, be treated in the framework derived by Fatuzzo and Labrune for ferroelectric domains [28,36], once the v(B) curve has been determined.…”

Magnetic properties, domain-wall creep motion, and the Dzyaloshinskii-Moriya interaction in Pt/Co/Ir thin films

“…heavy-metal/ferromagnet trilayers as an interfacial effect. The trend with Co thickness shows that we might expect there to be no net DM field in Pt/Co/Ir films with Co layers thicker than 3.8 nm, at which point the dominance of in-plane volume magnetic anisotropy indicates that the magnetic properties have become less dependent on the interfaces [20]. Interfacial effects are generally expected to scale as 1/t.…”

“…We study the magnetic properties of a series of thin films of Ta (4.5 nm)/Pt (4 nm)/Co (t)/Ir (5 nm), with Co thickness t varying between 0.56 and 1.1 nm, deposited onto thin glass substrates by dc magnetron sputtering [20]. The magnetic properties were measured by a combination of SQUID-VSM magnetometry and magneto-optical Kerr effect (MOKE) microscopy.…”

“…The magnetic properties were measured by a combination of SQUID-VSM magnetometry and magneto-optical Kerr effect (MOKE) microscopy. The magnetic anisotropy field H k was measured both from in-plane SQUID-VSM hysteresis loops and from polar MOKE versus in-plane field moment rotation (similar to the method used previously [20], with the change in the polar MOKE signal being proportional to the change in the out-of-plane magnetization component). The results from the two methods are consistent, with the values from the Kerr method used here, since this measurement technique is local to the region of the film where the domain-wall velocities are measured.…”