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Jungfleisch, Matthias B.

Publications and source records attributed to Jungfleisch, Matthias B..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Spincaloritronic Measurements: A Round Robin Comparison of the Longitudinal Spin Seebeck Effect

The rising field of spin caloritronics focuses on the interactions between spin and heat currents in a magnetic material; the observation of the spin Seebeck effect opened the route to this branch of research. This paper reports the results of a round robin test performed by five partners on a single device highlighting the reproducibility problems related to the measurements of the spin Seebeck coefficient, the quantity that describes the strength of the spin Seebeck effect. Here, this work stimulated the search for more reproducible measurement methods through the analysis of the systematic effects.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Linear and nonlinear spin-wave dynamics in ultralow-damping microstructured Co 2 FeAl Heusler waveguide

Here, we report on the investigation of linear and nonlinear spin-wave dynamics of a microstructured Co 2 FeAl Heusler waveguide using the microfocus Brillouin light scattering technique. A significantly increased decay length of 19.55 μm owing to decreased Gilbert damping has been observed for waves propagating in the linear regime. Furthermore, the localized edge mode caused by the demagnetizing field leads to the nonlinear generation of high-order harmonics at double and triple excitation frequencies at high powers. The obtained results provide valuable insights into the linear and nonlinear spin wave dynamics of the Heusler waveguide and could potentially be applied in the implementation of spin wave frequency multipliers for magnonic applications.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Control of Terahertz Emission by Ultrafast Spin-Charge Current Conversion at Rashba Interfaces

Here, we show that a femtosecond spin-current pulse can generate terahertz (THz) transients at Rashba interfaces between two nonmagnetic materials. Our results unambiguously demonstrate the importance of the interface in this conversion process that we interpret in terms of the inverse Rashba Edelstein effect, in contrast to the THz emission in the bulk conversion process via the inverse spin-Hall effect. Furthermore, we show that at Rashba interfaces the THz-field amplitude can be controlled by the helicity of the light. The optical generation of electric photocurrents by these interfacial effects in the femtosecond regime will open up new opportunities in ultrafast spintronics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Measurements of long-wavelength spin waves for the magnetic field in the Damon-Eshbach, backward-volume and forward-volume geometries of an yttrium iron garnet film

In this paper, we report systematic measurements of the dispersion of long wavelength spin waves for a wide range of wave vectors for the magnetic field along the three principal directions defining the forward volume, backward volume and Damon-Eshbach modes of a 9.72 μm thick film of an yttrium iron garnet obtained using lithographically patterned, multi-element, spatially resonant, antennas. Overall good agreement is found between the experimental data for the backward volume and Damon-Eshbach modes and the magnetostatic theory of Damon and Eshbach. Also, good agreement is found between the experimental data for the forward volume mode and the theory of Damon and van de Vaart.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Coupled macrospins: Mode dynamics in symmetric and asymmetric vertices

We report the microwave response of symmetric and asymmetric threefold clusters with nearly contacting segments that can serve as the node in a Kagome artificial spin ice lattice. The structures are patterned on a coplanar waveguide and consist of elongated and nearly-contacting ellipses with uniform thickness. Branches of the ferromagnetic resonance spectra display mode softening that correlates well with the calculations, whereas agreement between the measured and simulated static magnetization is more qualitative.

36 MATERIALS SCIENCE↗
DOE OSTI2017

High-Frequency Dynamics Modulated by Collective Magnetization Reversal in Artificial Spin Ice

Spin-torque ferromagnetic resonance arises in heavy metal-ferromagnet heterostructures when an alternating charge current is passed through the bilayer stack. The methodology to detect the resonance is based on the anisotropic magnetoresistance, which is the change in the electrical resistance due to different orientations of the magnetization. In connected networks of ferromagnetic nanowires, known as artificial spin ice, the magnetoresistance is rather complex owing to the underlying collective behavior of the geometrically frustrated magnetic domain structure. Here, we demonstrate spin-torque ferromagnetic resonance investigations in a square artificial spin-ice system and correlate our observations to magneto-transport measurements. The experimental findings are described using a simulation approach that highlights the importance of the correlated dynamics response of the magnetic system. Here, our results open the possibility of designing reconfigurable microwave oscillators and magnetoresistive devices based on connected networks of nanomagnets.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Excitation of the three principal spin waves in yttrium iron garnet using a wavelength-specific multi-element antenna

We report systematic measurements of the dispersion of long wavelength spin waves for the magnetic field along the three principal directions (supporting the forward volume, backward volume and Damon-Eshbach modes) of a 3.05 um thick yttrium iron garnet film on a lattice-matched (111) gadolinium gallium garnet substrate obtained using a lithographically patterned, multi-element, 50 um spatially-resonant, antenna.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Terahertz emission from ultrafast spin and charge currents at a Rashba interface

Abstract: We demonstrate the efficient single-cycle THz emission from a Rashba interface, i.e., Ag/Bi, in a spintronic heterostructure. Different from the previously reported inversed spin Hall effect mechanism in bulk systems, the observed ultrafast spin-to-charge conversion in a 2D Rashba interface is due to the inversed Rashba-Edelstein effect.

Zhang, Qi↗
DOE OSTI2016

Insulating nanomagnets driven by spin torque

Magnetic insulators, such as yttrium iron garnet (Y 3 Fe 5 O 12 ), are ideal materials for ultra-low power spintronics applications due to their low energy dissipation and efficient spin current generation and transmission. Recently, it has been realized that spin dynamics can be driven very effectively in micrometer-sized Y 3 Fe 5 O 12 /Pt heterostructures by spin-Hall effects. We demonstrate here the excitation and detection of spin dynamics in Y 3 Fe 5 O 12 /Pt nanowires by spin-torque ferromagnetic resonance. The nanowires defined via electron-beam lithography are fabricated by conventional room temperature sputtering deposition on Gd 3 Ga 5 O 12 substrates and lift-off. We observe field-like and anti-damping-like torques acting on the magnetization precession, which are due to simultaneous excitation by Oersted fields and spin-Hall torques. The Y 3 Fe 5 O 12 /Pt nanowires are thoroughly examined over a wide frequency and power range. We observe a large change in the resonance field at high microwave powers, which is attributed to a decreasing effective magnetization due to microwave absorption. By comparing different nanowire widths, the importance of geometrical confinements for magnetization dynamics becomes evident. In conclusion, our results are the first stepping stones toward the realization of integrated magnonic logic devices based on insulators, where nanomagnets play an essential role.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Perspective: Interface generation of spin-orbit torques

We present that most of the modern spintronics developments rely on the manipulation of magnetization states via electric currents, which started with the discovery of spin transfer torque effects 20 years ago. By now, it has been realized that spin-orbit coupling provides a particularly efficient pathway for generating spin torques from charge currents. At the same time, spin-orbit effects can be enhanced at interfaces, which opens up novel device concepts. Here, we discuss two examples of such interfacial spin-orbit torques, namely, systems with inherently two-dimensional materials and metallic bilayers with strong Rashba spin-orbit coupling at their interfaces. We show how ferromagnetic resonance excited by spin-orbit torques can provide information about the underlying mechanisms. In addition, this article provides a brief overview of recent developments with respect to interfacial spin-orbit torques and an outlook of still open questions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Spin Hall effects in metallic antiferromagnets – perspectives for future spin-orbitronics

We investigate angular dependent spin-orbit torques from the spin Hall effect in a metallic antiferromagnet using the spin-torque ferromagnetic resonance technique. The large spin Hall effect exists in PtMn, a prototypical CuAu-I-type metallic antiferromagnet. By applying epitaxial growth, we previously reported an appreciable difference in spin-orbit torques for c- and a-axis orientated samples, implying anisotropic effects in magnetically ordered materials. In this work we demonstrate through bipolar-magnetic-field experiments a small but noticeable asymmetric behavior in the spin-transfer-torque that appears as a hysteresis effect. We also suggest that metallic antiferromagnets may be good candidates for the investigation of various unidirectional effects related to novel spin-orbitronics phenomena.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Spin Vortex Resonance in Non-planar Ferromagnetic Dots

In planar structures, the vortex resonance frequency changes little as a function of an in-plane magnetic field as long as the vortex state persists. Altering the topography of the element leads to a vastly different dynamic response that arises due to the local vortex core confinement effect. In this work, we studied the magnetic excitations in non-planar ferromagnetic dots using a broadband microwave spectroscopy technique. Two distinct regimes of vortex gyration were detected depending on the vortex core position. The experimental results are in qualitative agreement with micromagnetic simulations.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Spin Hall effects in metallic antiferromagnets – perspectives for future spinorbitronics

We investigate angular dependent spin-orbit torques from the spin Hall effect in a metallic antiferromagnet using the spin-torque ferromagnetic resonance technique. The large spin Hall effect exists in PtMn, a prototypical CuAu-I-type metallic antiferromagnet. By applying epitaxial growth, we previously reported an appreciable difference in spin-orbit torques for c- and a-axis orientated samples, implying anisotropic effects in magnetically ordered materials. In this work we demonstrate through bipolar-magnetic-field experiments a small but noticeable asymmetric behavior in the spin-transfer-torque that appears as a hysteresis effect. We also suggest that metallic antiferromagnets may be good candidates for the investigation of various unidirectional effects related to novel spin-orbitronics phenomena.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Research update: Spin transfer torques in permalloy on monolayer MoS 2

We observe current induced spin transfertorque resonance in permalloy (Py) grown on monolayer MoS 2 . By passing rf current through the Py/MoS 2 bilayer, field-like and damping-like torques are induced which excite the ferromagnetic resonance of Py. The signals are detected via a homodyne voltage from anisotropic magnetoresistance of Py. In comparison to other bilayer systems with strong spin-orbit torques, the monolayer MoS 2 cannot provide bulk spin Hall effects and thus indicates the purely interfacial nature of the spin transfer torques. Furthermore, our results indicate the potential of two-dimensional transition-metal dichalcogenide for the use of interfacial spin-orbitronics applications.

36 MATERIALS SCIENCE↗
DOE OSTI2016

All-electrical detection of spin dynamics in magnetic antidot lattices by the inverse spin Hall effect

The understanding of spin dynamics in laterally confined structures on sub-micron length scales has become a significant aspect of the development of novel magnetic storage technologies. Numerous ferromagnetic resonance measurements, optical characterization by Kerr microscopy and Brillouin light scattering spectroscopy and x-ray studies were carried out to detect the dynamics in patterned magnetic antidot lattices. Here, we investigate Oersted-field driven spin dynamics in rectangular Ni80Fe20/Pt antidot lattices with different lattice parameters by electrical means. When the system is driven to resonance, a dc voltage across the length of the sample is detected that changes its sign upon field reversal, which is in agreement with a rectification mechanism based on the inverse spin Hall effect. Furthermore, we show that the voltage output scales linearly with the applied microwave drive in the investigated range of powers. Lastly, our findings have direct implications on the development of engineered magnonics applications and devices.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Driving and detecting ferromagnetic resonance in insulators with the spin Hall effect

We demonstrate the generation and detection of spin-torque ferromagnetic resonance in Pt/Y 3 Fe 5 O 12 (YIG) bilayers. A unique attribute of this system is that the spin Hall effect lies at the heart of both the generation and detection processes and no charge current is passing through the insulating magnetic layer. When the YIG undergoes resonance, a dc voltage is detected longitudinally along the Pt that can be described by two components. One is the mixing of the spin Hall magnetoresistance with the microwave current. The other results from spin pumping into the Pt being converted to a dc current through the inverse spin Hall effect. The voltage is measured with applied magnetic field directions that range in-plane to nearly perpendicular. In conclusion, we find that for magnetic fields that are mostly out-of-plane, an imaginary component of the spin mixing conductance is required to model our data.

36 MATERIALS SCIENCE↗