Towards a table-top microscope for nanoscale magnetic imaging using picosecond thermal gradients

Bartell, Jason; Ngai, Darryl; Leng, Zhaoqi; Fuchs, Gregory D.

doi:10.1038/ncomms9460

Cited by 27 publications

(69 citation statements)

References 30 publications

(36 reference statements)

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“…A microwave source is synchronized with a fast-pulsed light source, and the light measures or images the magnetization via a magneto-optical effect such as Kerr rotation or x-ray magnetic circular dichroism [22–32]. An interesting variation on the stroboscopic method is an electrical measurement of the Nernst voltage under microwave excitation and pulsed laser heating [33–35]. Previously, we reported a phase-sensitive, magneto-optical FMR detection method using a stroboscopic method with light modulated at the resonance frequency [36].…”

Section: Introductionmentioning

confidence: 99%

Phase-resolved ferromagnetic resonance using a heterodyne detection method

2016

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This paper describes a phase-resolved ferromagnetic resonance (FMR) measurement using a heterodyne method. Spin precession is driven by microwave fields and detected by 1550 nm laser light that is modulated at a frequency slightly shifted with respected to the FMR driving frequency. The evolving phase difference between the spin precession and the modulated light produces a slowly oscillating Kerr rotation signal with a phase equal to the precession phase plus a phase due to the path length difference between the excitation microwave signal and the optical signal. We estimate the accuracy of the precession phase measurement to be 0.1 rad. This heterodyne FMR detection method eliminates the need for field modulation and allows a stronger detection signal at higher intermediate frequency where the 1/f noise floor is reduced.

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Section: Introductionmentioning

confidence: 99%

Phase-resolved ferromagnetic resonance using a heterodyne detection method

2016

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“…To extend LSSE imaging into the time-domain, we use picosecond laser heating to stroboscopically sample magnetization. We have previously shown, in metallic ferromagnets, that picosecond heating can be used for stroboscopic magnetic microscopy using the timeresolved anomalous Nernst effect (TRANE) [25]. In TRANE microscopy, the temporal resolution is set by the excitation and decay of a thermal gradient within a single material that both absorbs the heat from the laser pulse and produces a TRANE voltage from internal spinorbit interactions [26,27].…”

Section: Main Textmentioning

confidence: 99%

“…Additional details are available in the SI, and see Ref. [25] for a lengthier discussion of the procedure. The comparison of the spatiotemporal profile of the calculation and the known temperature dependence of resistivity enable us to calibrate the spatiotemporal temperature rise due to laser heating.…”

Section: Main Textmentioning

confidence: 99%

“…This relation is used to fit the FMR spectra to extract the amplitude, phase, linewidth, and resonant field. For more details on fitting see refs [25,38]. To demonstrate that the TRLSSE microscope is a phase-sensitive stroboscope, we rotated the phase of the microwave current by 180° and remeasure FMR.…”

Section: Main Textmentioning

confidence: 99%

“…Next, we quantify the sensitivity of TRLSSE microscopy for our ultra-thin YIG/Pt samples. It is important to note that the sensitivity is sample dependent through both sample geometry and the impedance match with the detection circuit [25].…”

Section: Main Textmentioning

confidence: 99%

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Imaging Magnetization Structure and Dynamics in Ultrathin Y3Fe5O12/Pt Bilayers with High Sensitivity Using the Time-Reso

et al. 2017

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8We demonstrate an instrument for time-resolved magnetic imaging that is highly sensitive to the 9 in-plane magnetization state and dynamics of thin-film bilayers of yttrium iron garnet 10 (Y 3 Fe 5 O 12, YIG)/Pt: the time-resolved longitudinal spin Seebeck (TRLSSE) effect microscope. 11We detect the local, in-plane magnetic orientation within the YIG by focusing a picosecond laser 12 to generate thermally-driven spin current from the YIG into the Pt by the spin Seebeck effect, 13 and then use the inverse spin Hall effect in the Pt to transduce this spin current to an output 14 voltage. To establish the time resolution of TRLSSE, we show that pulsed optical heating of 15 patterned YIG (20 nm)/Pt(6 nm)/Ru (2 nm) wires generates a magnetization-dependent voltage 16 pulse of less than 100 ps. We demonstrate TRLSSE microscopy to image both static magnetic 17 structure and gigahertz-frequency magnetic resonance dynamics with sub-micron spatial 18 resolution and a sensitivity to magnetic orientation below 0.3 deg/ in ultrathin YIG. 19 20 2

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Local Photothermal Control of Phase Transitions for On‐Demand Room‐Temperature Rewritable Magnetic Patterning

et al. 2020

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The ability to make controlled patterns of magnetic structures within a nonmagnetic background is essential for several types of existing and proposed technologies. Such patterns provide the foundation of magnetic memory and logic devices 1 , allow the creation of artificial spinice lattices 2,3 and enable the study of magnon propagation 4 . Here, we report a novel approach for magnetic patterning that allows repeated creation and erasure of arbitrary shapes of thin-film ferromagnetic structures. This strategy is enabled by epitaxial Fe 0.52 Rh 0.48 thin films designed so that both ferromagnetic and antiferromagnetic phases are bistable at room temperature. Starting with the film in a uniform antiferromagnetic state, we demonstrate the ability to write arbitrary patterns of the ferromagnetic phase by local heating with a focused laser. If desired, the results can then be erased by cooling with a thermoelectric cooler and the material repeatedly repatterned.Intermetallic Fe 1-x Rh x (B2, P m3m) exhibits a hysteretic antiferromagnetic/ferromagnetic transformation which has been harnessed to produce composite multiferroics exhibiting record-breaking magnetoelectric coupling coefficients 5 , magnetocaloric refrigerators with competitive cooling capabilities 6 and novel memories based on antiferromagnetic order 7 . In this study, we design epitaxial Fe 1-x Rh x films so that both ferromagnetic and antiferromagnetic states are simultaneously bistable at room temperature. We engineer the width of the thermal hysteresis to be sufficiently narrow to enable efficient controllability, but also wide enough to robustly withstand thermal perturbations. Moderate heating by a focused laser is used to locally drive antiferromagnetic regions controllably to the ferromagnetic phase, demonstrating the patterning of arbitrary magnetic features on the submicron scale. These findings present opportunities for writing and erasing high-fidelity magnetically active nanostructures that are of interest for magnonic crystals 8 , artificial spin-ice lattices 9 and memory 10 and logic devices 11 . FIG. 1.Fully-dense phase-pure untwinned epitaxial B2 Fe0.52Rh0.48/MgO(001) layers grown via molecular-beam epitaxy. a, RBS spectrum; labeled iron and rhodium spectral features correspond to a magnetically bistable rhodium fraction of 0.48. b, BF-TEM image of the entire film cross section together with c, a corresponding SAED pattern. Note the weaker film and more intense substrate reflections. d, XRD θ-2θ scan; film (violet) and substrate (orange) reflections are indexed. e, XRD ω-rocking scan about the 001 film peak.Fe 1-x Rh x films are grown epitaxially on singlecrystalline (001)-oriented MgO substrates using molecular-beam epitaxy. The fraction x of rhodium in the film is carefully tuned to 0.48, where the hysteretic antiferromagnet/ferromagnet phase transitions are centered near room temperature. Film compositions are confirmed via Rutherford backscattering spectrometry (RBS) measurements (Fig. 1a) using the areal ratio of corresponding iron and...

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Towards a table-top microscope for nanoscale magnetic imaging using picosecond thermal gradients

Cited by 27 publications

References 30 publications

Phase-resolved ferromagnetic resonance using a heterodyne detection method

Phase-resolved ferromagnetic resonance using a heterodyne detection method

Imaging Magnetization Structure and Dynamics in Ultrathin Y3Fe5O12/Pt Bilayers with High Sensitivity Using the Time-Reso

Local Photothermal Control of Phase Transitions for On‐Demand Room‐Temperature Rewritable Magnetic Patterning

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