skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Engineering the Spectrum of Dipole Field-Localized Spin-Wave Modes to Enable Spin-Torque Antidamping

Authors:
; ; ; ; ; ; ;
Publication Date:
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1358642
Grant/Contract Number:
FG02-03ER46054
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Physical Review Applied
Additional Journal Information:
Journal Volume: 7; Journal Issue: 5; Related Information: CHORUS Timestamp: 2017-05-25 22:09:07; Journal ID: ISSN 2331-7019
Publisher:
American Physical Society
Country of Publication:
United States
Language:
English

Citation Formats

Zhang, Chi, Pu, Yong, Manuilov, Sergei A., White, Shane P., Page, Michael R., Blomberg, Erick C., Pelekhov, Denis V., and Hammel, P. Chris. Engineering the Spectrum of Dipole Field-Localized Spin-Wave Modes to Enable Spin-Torque Antidamping. United States: N. p., 2017. Web. doi:10.1103/PhysRevApplied.7.054019.
Zhang, Chi, Pu, Yong, Manuilov, Sergei A., White, Shane P., Page, Michael R., Blomberg, Erick C., Pelekhov, Denis V., & Hammel, P. Chris. Engineering the Spectrum of Dipole Field-Localized Spin-Wave Modes to Enable Spin-Torque Antidamping. United States. doi:10.1103/PhysRevApplied.7.054019.
Zhang, Chi, Pu, Yong, Manuilov, Sergei A., White, Shane P., Page, Michael R., Blomberg, Erick C., Pelekhov, Denis V., and Hammel, P. Chris. Thu . "Engineering the Spectrum of Dipole Field-Localized Spin-Wave Modes to Enable Spin-Torque Antidamping". United States. doi:10.1103/PhysRevApplied.7.054019.
@article{osti_1358642,
title = {Engineering the Spectrum of Dipole Field-Localized Spin-Wave Modes to Enable Spin-Torque Antidamping},
author = {Zhang, Chi and Pu, Yong and Manuilov, Sergei A. and White, Shane P. and Page, Michael R. and Blomberg, Erick C. and Pelekhov, Denis V. and Hammel, P. Chris},
abstractNote = {},
doi = {10.1103/PhysRevApplied.7.054019},
journal = {Physical Review Applied},
number = 5,
volume = 7,
place = {United States},
year = {Thu May 25 00:00:00 EDT 2017},
month = {Thu May 25 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1103/PhysRevApplied.7.054019

Save / Share:
  • We studied spin-transfer-torque (STT) switching of a cross-shaped magnetic tunnel junction in a recent report [Roy et al., J. Appl. Phys. 113, 223904 (2013)]. In that structure, the free layer is designed to have four stable energy states using the shape anisotropy of a cross. STT switching showed different regions with increasing current density. Here, we employ the micromagnetic spectral mapping technique in an attempt to understand how the asymmetry of cross dimensions and spin polarization direction of the injected current affect the magnetization dynamics. We compute spatially averaged frequency-domain spectrum of the time-domain magnetization dynamics in the presence ofmore » the current-induced STT term. At low currents, the asymmetry of polarization direction and that of the arms are observed to cause a splitting of the excited frequency modes. Higher harmonics are also observed, presumably due to spin-wave wells caused by the regions of spatially non-uniform effective magnetic field. The results could be used towards designing a multi-bit-per-cell STT-based random access memory with an improved storage density.« less
  • We use high-resolution imaging to study the propagation of spin waves in magnonic waveguides created by the dipolar magnetic fields of microscopic patterns. We show that the characteristics of spin-wave modes in such waveguides depend strongly on their geometry. In particular, by tuning the geometrical parameters, field-induced confinement for both the edge and the center waveguide modes can be achieved, enabling control over the spin-wave transmission characteristics. The studied waveguiding structures are particularly promising for the implementation of magnonic devices utilizing spin-torque phenomena.
  • The dipole field from a probe magnet can be used to localize a discrete spectrum of standing spin wave modes in a continuous ferromagnetic thin film without lithographic modification to the film. Obtaining the resonance field for a localized mode is not trivial due to the effect of the confined and inhomogeneous magnetization precession. We compare the results of micromagnetic and analytic methods to find the resonance field of localized modes in a ferromagnetic thin film, and investigate the accuracy of these methods by comparing with a numerical minimization technique that assumes Bessel function modes with pinned boundary conditions. Wemore » find that the micromagnetic technique, while computationally more intensive, reveals that the true magnetization profiles of localized modes are similar to Bessel functions with gradually decaying dynamic magnetization at the mode edges. We also find that an analytic solution, which is simple to implement and computationally much faster than other methods, accurately describes the resonance field of localized modes when exchange fields are negligible, and demonstrating the accessibility of localized mode analysis.« less
  • Cited by 2
  • The influence of dynamic coupling in between magnetic layers of a standard spin torque nano-oscillator composed of a synthetic antiferromagnet (SyF) as a polarizer and an in-plane magnetized free layer has been investigated. Experiments on spin valve nanopillars reveal non-continuous features such as kinks in the frequency field dependence that cannot be explained without such interactions. Comparison of experiments to numerical macrospin simulations shows that this is due to non-linear interaction between the spin torque (STT) driven mode and a damped mode that is mediated via the third harmonics of the STT mode. It only occurs at large applied currentsmore » and thus at large excitation amplitudes of the STT mode. Under these conditions, a hybridized mode characterized by a strong reduction of the linewidth appears. The reduced linewidth can be explained by a reduction of the non-linear contribution to the linewidth via an enhanced effective damping. Interestingly, the effect depends also on the exchange interaction within the SyF. An enhancement of the current range of reduced linewidth by a factor of two and a reduction of the minimum linewidth by a factor of two are predicted from simulation when the exchange interaction strength is reduced by 30%. These results open directions to optimize the design and microwave performances of spin torque nano-oscillators taking advantage of the coupling mechanisms.« less