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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,387 records · Page 77
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Strong Coupling between Magnons and Microwave Photons in On-Chip Ferromagnet-Superconductor Thin-Film Devices

We show superconducting resonator. A coupling strength of 0.152 GHz and a cooperativity of 68 are found for a 30-nm-thick Permalloy stripe. The coupling strength is tunable by rotating the biasing magnetic field or changing the volume of Permalloy. We also observe an enhancement of magnon-photon coupling in the nonlinear regime of the superconducting resonator, which is attributed to the nucleation of dynamic flux vortices. Our results demonstrate a critical step towards future integrated hybrid systems for quantum magnonics and on-chip coherent information transfer.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Bloch Chirality Induced by an Interlayer Dzyaloshinskii-Moriya Interaction in Ferromagnetic Multilayers

Chiral spin textures stabilized by the interfacial Dzyaloshinkii-Moriya interaction, such as skyrmions and homochiral domain walls, have been shown to exhibit qualities that make them attractive for their incorporation in a variety of spintronic devices. However, for thicker multilayer films, mixed textures occur in which an achiral Bloch component coexists with a chiral Néel component of the domain wall to reduce the demagnetization field at the film surface. We show that an interlayer Dzyaloshinkii-Moriya interaction can break the degeneracy between Bloch chiralities. We further find large population asymmetries and chiral branching in the Bloch component of the domain walls in well-ordered Co/Pd multilayers. This asymmetry is a result of the combined effect of the demagnetization field and an interlayer Dzyaloshinkii-Moriya interaction, and is strongly related to film thickness and structural ordering. This work paves the way toward the utilization of this effect toward controlling Bloch chirality in magnetic multilayers.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Collective Ferromagnetism of Artificial Square Spin Ice

In this work, we study the temperature and magnetic field dependence of the total magnetic moment of large-area permalloy artificial square spin ice arrays. The temperature dependence and hysteresis behavior are consistent with the coherent magnetization reversal expected in the Stoner-Wohlfarth model, with clear deviations due to interisland interactions at small lattice spacing. Through micromagnetic simulations, we explore this behavior and demonstrate that the deviations result from increasingly complex magnetization reversal at small lattice spacing, induced by interisland interactions, and depending critically on details of the island shapes. These results establish new means to tune the physical properties of artificial spin ice structures and other interacting nanomagnet systems, such as patterned magnetic media.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Magnetic properties of single crystalline itinerant ferromagnet AlFe 2 B 2

Here, single crystals of AlFe 2 B 2 have been grown using the self-flux growth method, and then we measured the structural properties, temperature- and field-dependent magnetization, and temperature-dependent electrical resistivity at ambient as well as high pressure. The Curie temperature of AlFe 2 B 2 is determined to be 274 K. The measured saturation magnetization and the effective moment for the paramagnetic Fe ion indicate the itinerant nature of the magnetism with a Rhode-Wohlfarth ratio M C /M sat ≈ 1.14. Temperature-dependent resistivity measurements under hydrostatic pressure show that transition temperature T C is suppressed down to 255 K for p = 2.24 GPa pressure with a suppression rate of ~–8.9 K/GPa. The anisotropy fields and magnetocrystalline anisotropy constants are in reasonable agreement with density functional theory calculations.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Programmable bias field observed in graded ferromagnetic semiconductor films with broken symmetry

We report on the observation of a field-induced magnetic bias effect in a Ga 0.94 Mn 0.06 As 1-y P y thin film with digitally graded phosphorus content. Although phosphorus concentration in the sample is changed in steps from y approximate to 0.03 to y approximate to 0.28, the magnetometry and magnetotransport data display a coherent magnetic response typical for single-layer in-plane magnetized films with cubic and weak [110] uniaxial anisotropy. Unexpectedly, low-temperature planar Hall resistance loops exhibit remarkable asymmetry tunable by application of strong in-plane initial magnetic field H Ini . We discuss this unusual memory effect, resembling the magnetization asymmetry in the exchange biased magnetic bilayers, in terms of a unidirectional bias field H b induced by H Ini . We show that such bias field defines the delayed or accelerated nucleation of domains with chiral domain walls performing the magnetization reversal.

36 MATERIALS SCIENCE↗