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EQUATE/NCMN Seminar w/ Abdelghani Laraoui

Studying Nanoscale Magnetic Phenomena in Magnetic Thin Films Using Diamond Magnetic Microscopy

4:00 pm – 5:00 pm
Jorgensen Hall Room: 110
Target Audiences:
Magnetic microscopy based on diamond nitrogen vacancy (NV) quantum sensors has become a versatile tool to detect magnetic fields in magnetic materials with a unique combination of spatial resolution and magnetic sensitivity [1-4]. In this seminar, I will present two examples of using NV magnetic microscopy in both confocal microscopy (CFM) and scanning probe microscopy (SPM) geometries to study nanoscale magnetic phenomena in different materials.
First, I will discuss recent NV-CFM measurements of spin-wave transport in ferrimagnetic insulator thulium iron garnet (TmIG) thin films. Spin waves (SWs) are dynamic magnetic excitations of magnetically ordered systems. They can be generated by injecting current or microwave and are being explored for magnon spintronics, low-energy logical operations, and as quantum buses. NV magnetometry allows probing of SWs at the sub-micrometer scale, seen by the amplification of the local microwave magnetic field due to the coupling of NV spins with the stray-field produced by the SWs. By monitoring the NV optically detected magnetic resonance contrast, we map SWs in TmIG thin films (thickness of 34 nm) and measure their amplitude, decay length (~ 50 mm), and SW wavelength in the range of 0.6 - 2 mm that depends strongly on the amplitude of the applied magnetic field [5].
Then, I will discuss NV-SPM measurements of skyrmions in CoxPt1-x gradient single-crystal films (thickness 10 -30 nm), where stoichiometric coefficient x is engineered to vary continuously from the top surface to the bottom interface. Skyrmions are topological spin textures in magnetic systems where strong spin orbit coupling and broken inversion symmetry lead to Dzyaloshinskii-Moriya interaction (DMI). We visualize different topological spin textures (skyrmions, anti-skyrmions) using NV magnetometry in combination with magnetic force microscopy and micromagnetic simulations. Furthermore, I will discuss the effect of CoxPt1-x thickness, DMI sign, and applied magnetic field on their size and chirality [6].

[1] I. Fescenko, A. Laraoui, et al., Phys. Rev. App. 11, 034029 (2019). [2] A. Laraoui and K. Ambal, Appl. Phys. Lett. 121, 060502 (2022). [3] A. Erickson, A. Laraoui, et al., RSC Adv. 13, 178 (2023). [4] S. Lamichhane, A. Laraoui, et al., ACS Nano 17, 9, 8694 (2023). [5] R. Timalsina, A. Laraoui, et al., Adv. Mat., under submission (2023). [6] A. Erickson, A. Laraoui, et al., Nat. Nano., under preparation (2023).

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