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Search Publications by: Robert D. McMichael (Fed)

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Displaying 1 - 25 of 160

Simplified algorithms for adaptive experiment design in parameter estimation

November 1, 2022
Author(s)
Robert D. McMichael, Sean Blakley
In experiments to estimate parameters of a parametric model, Bayesian experiment design allows measurement settings to be chosen based on utility, i.e. the predicted improvement of parameter distributions due to modeled measurement results. In this paper

Robust spin relaxometry with fast adaptive Bayesian estimation

June 15, 2022
Author(s)
Michael Caouette-Mansour, Adrian Solyom, Brandon Ruffolo, Robert D. McMichael, Jack Childress (Sankey), Lilian Childress
Spin relaxometry with nitrogen-vacancy (NV) centers in diamond offers a spectrally selective, atomically localized, and calibrated measurement of microwave-frequency magnetic noise, presenting a versatile probe for condensed matter and biological systems

Advances in Magnetometry Through Miniaturization

October 12, 2021
Author(s)
A Edelstein, J Burnette, Greg Fischer, S F. Cheng, William F. Egelhoff Jr., Robert McMichael, E Nowak
Recent innovations may lead to magnetic sensors that are smaller, more sensitive and/or cost less than current magnetometers. Examples of this are the chip scale atomic magnetometer, magnetic tunnel junctions with MgO barriers, and a device for minimizing

Annealing Temperature Dependences of Magnetization Reversal in Exchange Biased Bilayers

October 12, 2021
Author(s)
C G. Lee, V S. Gornakov, B H. Koo, K S. Shin, Robert McMichael, Andrew P. Chen, William F. Egelhoff Jr.
The thermal stability of the hysteretic properties and domain structures of exchange-coupled Co-Fe/Ir-Mn and Ni-Fe/Ir-Mn bilayers was studied. Using the magneto-optical indicator film technique, X-ray diffractometry, and VSM, we have revealed that the

Artifacts That Could Be Misinterpreted as Ballistic Magnetoresistance

October 12, 2021
Author(s)
William F. Egelhoff Jr., L Gan, Erik B. Svedberg, Cedric J. Powell, Alexander J. Shapiro, Robert McMichael, J Mallett, Thomas P. Moffat, Mark D. Stiles
Theoretical physics suggests that very large magnetoresistance (MR) values might be found in certain magnetic nanocontacts if a magnetic domain wall could be localized in them with a length scale that would allow conduction electrons to transit the wall

Challenges for Sub-PicoTesla Magnetic-Tunnel-Junction Sensors

October 12, 2021
Author(s)
Robert McMichael, Philip Pong, John Unguris, William F. Egelhoff Jr., A Edelstein, E Nowak, Sean R. Parkin
The extension of small, inexpensive, low-power magnetic sensors into the sub-picoTesla regime, which is currently dominated by fluxgates and SQUIDS, would be a paradigm shift for the field of magnetic sensors. The necessary elements for sub-picoTesla MTJ

Composition-based Reduction of Damping in Fe1-xVx (50nm) Thin Films

October 12, 2021
Author(s)
L Cheng, H Song, J O. Rantschler, Robert McMichael, William E. Bailey
The reduction of GHz damping a is a critical and unaddressed need in ferromagnetic materials development. Smith has predicted that the signal-to-noise ratios of nanoscale / Ghz spin electronic sensors will be inversely dependent on the free magnetic layer

Ferromagnetic Resonance Line Width in Inhomogeneous Thin Films

October 12, 2021
Author(s)
Robert McMichael, A B. Kunz, D J. Twisselmann
The dynamic properties of magnetic materials are important for magnetic data storage. The primary measurement technique for understanding magnetization damping is ferromagnetic resonance line width. Because materials inhomogeneities increase experimental

The Suppression of Orange-Peel Coupling in Magnetic Tunnel Junctions by Pre-Oxidation

October 12, 2021
Author(s)
William F. Egelhoff Jr., Robert McMichael, Cindi L. Dennis, Mark D. Stiles, Alexander J. Shapiro, Brian B. Maranville, Cedric J. Powell
We have have found that pre-oxidation of the bottom Co electrode in magnetic tunnel junctions (MTJs) very effectively suppresses orange-peel coupling. The result is a free layer that is much softer. Work by others has demonstrated that pre-oxidation is

Thin Film Edge Property Measurements by Edge Saturation

October 12, 2021
Author(s)
Brian B. Maranville, Robert McMichael, Cindi L. Dennis, C A. Ross, J Cheng
Two techniques are described for characterizing the magnetic properties of the edges in long, straight magnetic stripes, using vector magnetometry. The critical transverse field at which the edge magnetization saturates is determined by measuring

Sequential Bayesian experiment design for adaptive Ramsey sequence measurements.

October 11, 2021
Author(s)
Robert D. McMichael, Sergey Dushenko, Sean Blakley
The Ramsey sequence is a canonical example of a quantum phase determination for a spin qubit, but when readout fidelity is low, as with NV centers, measurement efficiency can be increased by focusing measurement resources on the most productive settings

optbayesexpt: Sequential Bayesian Experiment Design for Adaptive Measurements

February 3, 2021
Author(s)
Robert McMichael, Sean M. Blakley, Sergey Dushenko
Optbayesexpt is a free, open-source python package that provides adaptive algorithms for efficient estimation/measurement of parameters in a model function. Parameter estimation is the type of measurement one would conventionally tackle with a sequence of

Comparison of measured and simulated spin-wave mode spectra of magnetic nanostructures

January 6, 2021
Author(s)
Hans Nembach, Robert McMichael, Michael Schneider, Justin Shaw, Thomas J. Silva
Motivated by the importance of magnetization dynamics in nanomagnets for the development and optimization of magnetic devices and sensors, we measured and modeled spin wave spectra in patterned elliptical nanomagnets. Ferromagnetic resonance spectra for

Scalable microresonators for room-temperature detection of electron spin resonance from dilute, sub-nanoliter volume solids

October 28, 2020
Author(s)

Nandita S. Abhyankar, Amit K. Agrawal, Pragya R. Shrestha, Russell A. Maier, Robert D. McMichael, Jason P. Campbell, Veronika A. Szalai

Microresonators used for spin detection in volume-limited samples suffer from poor quality factors, which adversely affect sensitivity and ease of coupling to the microwave source. Here we adapt a metamaterial design with toroidal moment to confine

Quasi-two-dimensional magnon identification in antiferromagnetic FePS3 via magneto-Raman spectroscopy

February 18, 2020
Author(s)
Amber D. McCreary, Jeffrey R. Simpson, Thuc T. Mai, Robert D. McMichael, Jason E. Douglas, Nicholas P. Butch, Cindi L. Dennis, Rolando Valdes Aguilar, Angela R. Hight Walker
Recently it was discovered that van der Waals-bonded magnets retain long range magnetic ordering even down to a monolayer thickness, opening many avenues in fundamental physics and potential applications of these fascinating materials. One example is FePS3

Optimal Bayesian Experimental Design

September 4, 2019
Author(s)
Robert D. McMichael
This manual describes an implementation of optimal Bayesian experimental design methods. These methods address routine measurements where data are fit to experimental models in order to obtain model parameters. The twin benefits of these methods are

Spin-torque excitation of perpendicular standing spin waves in coupled YIG/Co heterostructures

March 23, 2018
Author(s)
Stefan Klinger, Vivek P. Amin, Stephan Gepraegs, Kathrin Ganzhorn, Hannes Maier-Flaig, Matthias Althammer, Hans Huebl, Rudolf Gross, Robert McMichael, Mark D. Stiles, Sebastian Goennenwein, Mathias Weiler
We investigate yttrium iron garnet (YIG)/cobalt (Co) heterostructures using broadband ferromagnetic resonance (FMR). We observe an efficient excitation of perpendicular standing spin waves (PSSWs) in the YIG layer when the resonance frequencies of the YIG

Spin-wave propagation in cubic anisotropy materials

June 30, 2017
Author(s)
Koji Sekiguchi, Seo-Won Lee, Hiroaki Sukegawa, Nana Sato, Se-Hyeok Oh, Robert McMichael, Kyung-Jin Lee
The information carrier of modern technologies is the electron charge whose transport inevitably generates Joule heating. Spin-wave, the collective precessional motion of electron spins, does not involve moving charges and thus alleviates Joule heating [1

Using Terahertz Waves to Identify the Presence of Goethite via Antiferromagnetic Resonance

April 24, 2017
Author(s)
Edward J. Garboczi, David F. Plusquellic, Robert D. McMichael, Virgil Provenzano, Paul E. Stutzman, Jack T. Surek, Shin G. Chou, Shuangzhen Wang
Virtually every corrosion detection method reports only the presence of a material phase denoting probable corrosion, not its spectral signature. A signature specific to the type of iron oxide corrosion would not only confirm the presence of corrosion but

Enhanced ferromagnetic resonance linewidth of the free layer in perpendicular magnetic tunnel junctions

March 3, 2017
Author(s)
Daniel B. Gopman, Cindi L. Dennis, Robert D. McMichael, Xiaojie Hao, Zihui Wang, Xiaobin Wang, Huadong Gan, Yuchen Zhou, Jian Zhang, Yiming Huai
We report the frequency dependence of the ferromagnetic resonance linewidth of the free layer in magnetic tunnel junctions with all perpendicular-to-the-plane magnetized layers. While the magnetic-fi eld-swept linewidth nominally shows a linear growth with

Spin wave localization in tangentially magnetized films

June 28, 2016
Author(s)
Elena V. Tartakovskaya, Martha Pardavi-Horvath, Robert McMichael
We present an analytical description of localized spin wave modes that form in a parabolic field minimum in a thin ferromagnetic film. Mode profiles proportional to Hermite functions are eigen-functions of the applied field and exchange parts of the