Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “MAGNETIC FILM”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Magnetic order of tetragonal CuO ultrathin films

Here, we present a detailed low-energy muon spin rotation and x-ray magnetic circular dichroism (XMCD) investigation of the magnetic structure in ultrathin tetragonal (T)-CuO films. The measured muon-spin polarization decay indicates an antiferromagnetic (AFM) order with a transition temperature higher than 200 K. The XMCD signal obtained around the CuL 2,3 edges indicates the presence of pinned Cu 2+ moments that are parallel to the sample surface, and additionally, isotropic paramagnetic moments. The pinning of some of the Cu moments is caused by an AFM ordering consisting of moments that lie most likely in plane of the film. Moreover, pinned moments show a larger orbital magnetic moment contribution with an approximate ratio of m orb /m spin =1.5, indicating that these spins are located at sites with reduced symmetry. Some fractions of the pinned moments remain pinned from an AFM background even at 360 K, indicating that T N >360K. We propose a simple model that explains these experimental findings, showing that the magnetic order of the T-CuO ultrathin films differs from the theoretical predictions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Magnetic Damping in Polycrystalline Thin-Film Fe-V Alloys

Here, we report on the magnetic damping properties of polycrystalline Fe-V alloy thin films that are deposited at room temperature. By varying the concentration of V in the alloy, the saturation magnetization can be adjusted from that of Fe to near zero.We show that exceptionally low values of the damping parameter can be maintained over the majority of this range, with a minimum damping at approximately 15%–20% V concentration. Such a minimum is qualitatively reproduced with ab initio calculations of the damping parameter, although at a concentration closer to 10% V. The measured intrinsic damping has a minimum value of (1.53±0.08)×10 –3 , which is approximately a factor of 3 higher than our calculated value of 0.48×10 –3 . From first-principles theory, we outline the factors that are mainly responsible for the trend of the damping parameter in these alloys. In particular, the band structure and resulting damping mechanism is shown to change at V concentrations greater than approximately 35% V content.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Probing Ice-Rule-Breaking Transition in Dy 2 Ti 2 O 7 Thin Film by Proximitized Transport and Magnetic Torque

While the spin-ice state of bulk pyrochlores such as Dy 2⁢ Ti 2 ⁢O 7 and Ho 2⁢ Ti 2 ⁢O 7 has been extensively studied in the past several decades due to its unique degenerate ground state and emergent monopole excitation, whether it survives in the thin-film form remains a mystery. The limited volume of the thin-film sample makes it challenging to study the intrinsic magnetic properties. Here, we synthesized 18-nm-thick Dy 2⁢ Ti 2 ⁢O 7 thin film on yttria-stabilized zirconia with 9.5 mol% Y 2 ⁢O 3 substrate and capped it by a thin conductive Bi 2 ⁢Ir 2 ⁢O 7 layer and performed the proximitized magnetoresistance measurements. Our Letter found that the ice-rule-breaking phase transition survives but with a modified effective nearest-neighbor interaction (𝐽 eff =1.054 K) and distorted Ising spin axes (𝜀 = +0.051) compared to the bulk crystal. Furthermore, the results are supported by the simultaneously measured capacitive torque magnetometry. Our Letter demonstrates that proximitized transport is an effective tool for thin films of insulating frustrated magnets.

Magnetic interactions↗
NASA NTRS1974

Investigation of the growth of garnet films by liquid phase epitaxy

Liquid phase expitaxy was investigated to determine its applicability to fabricating magnetic rare earth garnet films for spacecraft data recording systems. Two mixed garnet systems were investigated in detail: (1) Gd-Y and (2) Eu-Yb-Y. All films were deposited on Gd3Ga5012 substrates. The uniaxial anisotropy of the Gd-Y garnets is primarily stress-induced. These garnets are characterized by high-domain wall mobility, low coercivity and modest anisotropy. Characteristic length was found to be relatively sensitive to temperature. The Eu-Yb-Y garnets exhibit acceptable mobilities, good temperature stability and reasonable quality factors. The uniaxial anisotropy of these garnets is primarily growth-induced. The system is well suited for compositional "tailoring" to optimize specific desirable properties. Liquid phase epitaxy can be used to deposit Gd3Ga5012 spacing layers on magnetic garnet films and this arrangement possesses certain advantages over more conventional magnetic filmspacing layer combinations. However, it cannot be used if the magnetic film is to be ion implanted.

Moody, J. W.↗
DOE OSTI2020

Asymmetric crossing of the attractive and repulsive magnetic potential by Abrikosov vortices

Here, we present studies of Abrikosov vortex motion across the magnetically charged edges of long thin ferromagnetic stripes placed above or under a thin superconducting film. The magnetic charges at the stripe edges form attractive or repulsive potential wells for vortices. Using a relatively small in-plane magnetic field to polarize the stripe edges and normal-to-plane magnetic field to induce up or down polarized vortices, we tune the attractive or repulsive stripe-vortex interactions. Imaging of the vortex dynamics reveals that the repulsive magnetic potential U m + acts as a robust vortex pinning barrier, while the attractive U m - has practically no effect on the vortex motion irrespective of the position of the stripes located above or underneath the superconducting film. We analyze the observed asymmetry using equations of the overdamped vortex motion. The formal analytical solution yields an asymmetry, but the numerical modeling with and without noise terms does not confirm it. Instead, we find that the asymmetry is caused by the creation of spontaneous vortices at the maxima of U m , which depends on the edge polarity and suppress U m - . Furthermore, our experiment and time-dependent Ginzburg-Landau simulations demonstrate that magnetic pinning dominates over vortex pinning due to corrugations of the superconducting layer deposited on top of the ferromagnetic stripes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Magnetic ac susceptibility of superconducting Ta films for quantum computing

Recently, breakthroughs were reported in the long coherence time (>0.5 ms) transmon qubit using tantalum films (Ta). Identifying the loss mechanism in Ta films will help further improve the performance of Ta-based superconducting qubits. We report a study of superconducting properties in two sets of Ta films grown on c-cut and a-cut sapphires respectively using contact transport and noncontact magnetic ac susceptibility measurements. Although the resistive transition appears to be similar in both films, we found strikingly different responses in their complex magnetic susceptibilities χ' + iχ'$^{'}$ .χ'$^{'}$ in the c-cut films exhibits a sharp peak at superconducting transition Tc and becomes featureless below Tc indicating a strongly coupled superconducting state. In contrast, χ'$^{'}$ \ in the a-cut films exhibits a broad peak near Tc and a second peak appears below Tc, indicating granular superconductivity behavior. This second peak χ'$^{'}$ in is associated with the hysteresis loss at weak-link-type grain boundaries, which is believed to be a leading source of decoherence in the a-cut Ta films. The derived magnetic loss tangent in the a-cut films is about one order of magnitude higher than in the c-cut films. This study demonstrates that ac susceptibility is an excellent probe for characterizing bulk superconducting properties of the constituent superconducting materials used in qubits.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

Long-range magnetic order and relaxor ferroelectricity in a hexagonal high-entropy ferrite

Multiferroics that combine ferroelectricity and magnetic order are attractive for electronic and spintronic technologies, yet chemical disorder that promotes relaxor ferroelectricity usually suppresses long-range magnetic order. Here, we report entropy-stabilized relaxor multiferroicity in epitaxial hexagonal (Tb0.2Dy0.2Ho0.2Lu0.2Yb0.2)FeO3 thin films. Structural, magnetic, dielectric, and synchrotron spectroscopic measurements show the coexistence of relaxor ferroelectricity and long-range ferromagnetic order. We find that improper ferroelectricity remains robust against A-site configurational disorder, while the Fe sublattice preserves magnetic exchange. This separation of the microscopic origins of the polar and magnetic responses enables chemically disordered multiferroicity. Our results establish entropy engineering in hexagonal ferrites as a route toward multifunctional oxide thin films and provide a general design strategy for high-entropy multiferroics.

Miertschin, Duncan [Baylor University]↗
DOE OSTI2022

Manipulating the metal-to-insulator transition and magnetic properties in manganite thin films via epitaxial strain

Strain engineering of epitaxial transition metal oxide heterostructures offers an intriguing opportunity to control electronic structures by modifying the interplay between spin, charge, orbital, and lattice degrees of freedom. Here, we demonstrate that the electronic structure, magnetic and transport properties of La 0.9 Ba 0.1 MnO 3 thin films can be effectively controlled by epitaxial strain. Spectroscopic studies and first-principles calculations reveal that the orbital occupancy in Mn eg orbitals can be switched from the d 3z 2 -r 2 orbital to the d x 2 -y 2 orbital by varying the strain from compressive to tensile. Further, the change of orbital occupancy associated with Mn 3d-O 2p hybridization leads to dramatic modulation of the magnetic and electronic properties of strained La 0.9 Ba 0.1 MnO 3 thin films. Under moderate tensile strain, an emergent ferromagnetic insulating state with an enhanced ferromagnetic Curie temperature of 215 K is achieved. These findings not only deepen our understanding of electronic structures, magnetic and transport properties in the La 0.9 Ba 0.1 MnO 3 system, but also demonstrate the use of epitaxial strain as an effective knob to tune the electronic structures and related physical properties for potential spintronic device applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1987

Magnetic Liquids

Ferrofluidics Corporation's recent innovation is a spindle for rotating computer discs that supports the disc's rotating shaft on a film of magnetic fluid instead of conventional ball bearings. According to its developers, the spindle offers greatly increased rotational stability, meaning substantially reduced vibration and mechanical noise, and non- repeatable runout. This allows disc drives to store two to 10 times more information.

Source record↗
DOE OSTI2025

Magnetically dependent photovoltages in permalloy films and gratings

Significant photoinduced voltages observed in permalloy structures consist of two contributions with different origins, which depend on illumination conditions, structure geometry and magnetic field in distinct ways. The first component is the plasmon drag effect voltage closely associated with plasmon propagation. The second contribution is magnetically dependent and can be related to photoinduced gradients in the sample temperature and spin polarization. Possible mechanisms of the effect are discussed

36 MATERIALS SCIENCE↗
DOE OSTI2023

Electrical, optical, and magnetic properties of amorphous yttrium iron oxide thin films and consequences for non-local resistance measurements

We present magnetic characterization, charge resistivity, and optical photoluminescence measurements on amorphous yttrium iron oxide thin films ( ⁠a-Y–Fe–O), with supporting comparisons to amorphous germanium (⁠ a-Ge) films. We measured magnetic properties with both SQUID magnetometry and polarized neutron reflectometry. These results not only confirm that a-Y–Fe–O is a disordered magnetic material with strong predominantly antiferromagnetic exchange interactions and a high degree of frustration, but also that it is best understood electrically as a disordered semiconductor. As with amorphous germanium, a-Y–Fe–O obeys expectations for variable-range hopping through localized electron states over a wide range of temperature. We also clarify the consequences of charge transport through such a semiconducting medium for non-local voltage measurements intended to probe spin transport in nominally insulating magnetic materials. We further compare non-local resistance measurements made with “quasi-dc” automated current reversal to ac measurements made with a lock-in amplifier. These show that the “quasi-dc” measurement has an effective ac current excitation with frequency up to approximately 22 Hz, and that this effective ac excitation can cause artifacts in these measurements including incorrect sign of the non-local resistance. Here, this comprehensive investigation of non-local resistance measurements in a-Y–Fe–O shows no evidence of spin transport on micrometer length scales, which is contrary to our original work, and in line with more recent investigations by other groups.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Moving Pearl Vortices in Thin-Film Superconductors

The magnetic field h z of a moving Pearl vortex in a superconducting thin-film in (x,y) plane is studied with the help of the time-dependent London equation. It is found that for a vortex at the origin moving in +x direction, h z (x,y) is suppressed in front of the vortex, x>0, and enhanced behind (x<0). The distribution asymmetry is proportional to the velocity and to the conductivity of normal quasiparticles. The vortex self-energy and the interaction of two moving vortices are evaluated.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Switching between Magnetic Bloch and Néel Domain Walls with Anisotropy Modulations

It has been shown previously that the presence of a Dzyaloshinskii-Moriya interaction in perpendicularly magnetized thin films stabilizes N\'eel type domain walls. We demonstrate, using micromagnetic simulations and analytical modeling, that the presence of a uniaxial in-plane magnetic anisotropy can also lead to the formation of N\'eel walls in the absence of a Dzyaloshinskii-Moriya interaction. It is possible to abruptly switch between Bloch and N\'eel walls via a small modulation of both the in-plane, but also the perpendicular magnetic anisotropy. This opens up a route towards electric field control of the domain wall type with small applied voltages through electric field controlled anisotropies.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Atomic layer molecular beam epitaxy of kagome magnet RMn6Sn6 (R = Er, Tb) thin films

Kagome lattices have garnered substantial interest because their band structure consists of topological flat bands and Dirac cones. The RMn6Sn6 (R = rare earth) compounds are particularly interesting because of the existence of the large intrinsic anomalous Hall effect (AHE), which originates from the gapped Dirac cones near the Fermi level. This makes RMn6Sn6 an outstanding candidate for realizing the high-temperature quantum AHE. The growth of RMn6Sn6 thin films is beneficial for both fundamental research and potential applications. However, most of the studies on RMn6Sn6 have focused on bulk crystals, and the synthesis of RMn6Sn6 thin films has not been reported so far. Here, we report the atomic layer molecular beam epitaxy growth, structural and magnetic characterizations, and transport properties of ErMn6Sn6 and TbMn6Sn6 thin films. It is especially noteworthy that TbMn6Sn6 thin films have out-of-plane magnetic anisotropy, which is important for realizing the quantum AHE. Our work paves the avenue toward the control of the AHE using devices patterned from RMn6Sn6 thin films.

Materials Science↗
DOE OSTI2020

Recent Progress on Topological Structures in Ferroic Thin Films and Heterostructures

Topological spin/polarization structures in ferroic materials continue to draw great attention as a result of their fascinating physical behaviors and promising applications in the field of high-density nonvolatile memories as well as future energy-efficient nanoelectronic and spintronic devices. Such developments have been made, in part, based on recent advances in theoretical calculations, the synthesis of high-quality thin films, and the characterization of their emergent phenomena and exotic phases. Herein, progress over the last decade in the study of topological structures in ferroic thin films and heterostructures is explored, including the observation of topological structures and control of their structures and emergent physical phenomena through epitaxial strain, layer thickness, electric, magnetic fields, etc. First, the evolution of topological spin structures (e.g., magnetic skyrmions) and associated functionalities (e.g., topological Hall effect) in magnetic thin films and heterostructures is discussed. Then, the exotic polar topologies (e.g., domain walls, closure domains, polar vortices, bubble domains, and polar skyrmions) and their emergent physical properties in ferroelectric oxide films and heterostructures are explored. Lastly, a brief overview and prospectus of how the field may evolve in the coming years is provided.

36 MATERIALS SCIENCE↗