DCMPMS Seminars

Nanoscale real-space imaging of antiferromagnetic order using single point defect in Diamond

by Dr. Wasim Akhtar (Laboratoire Charles Coulomb, CNRS, Montpellier, France)

Tuesday, August 7, 2018 from to (Asia/Kolkata)
at AG80
Description
Point Defects in semiconductor have been deleterious, however very often such point defects occurring due to vacancy or unsaturated bonds in the crystal is accompanied by an electron spin. Such spin centers are the simplest two level quantum systems that can be manipulated using magnetic resonance techniques and are excellent candidate for Quantum-bits as well as for nanoscale magnetometry. In this talk I will discuss my current research which is based on identifying single point defect namely Nitrogen-Vacancy (NV) center in Diamond and exploiting its spin dependent photoluminescence for nanoscale magnetic field sensing and imaging, a topic of crucial importance from material science to mesoscopic physics and life sciences. A single NV center attached at the apex of the scanning AFM tip in combination with home-built confocal microscopy provides an atomic size, non-invasive, quantitative and vectorial magnetic field sensor [1]. The high magnetic-field sensitivity in combination with nanoscale spatial resolution of this magnetometer allowed us to image antiferromagnetic spin order in a magnetic thin film under ambient condition. We image the antiferromagnetic spin cycloid of a multiferroic BiFeO3 thin film and extract a period of ~70 nm, consistent with values determined previously by neutron diffraction technique. In addition, we take advantage of the magnetoelectric coupling present in BiFeO3 to manipulate the cycloid propagation direction by an electric field [2]. These results highlights that NV magnetometer has the uniqueness of being compatible with imaging and studying spin texture in antiferromagnetic thin films which are potential candidates for future spintronic/memory devices.

[1] L. Rondin et al., Rep. Prog. Phys. 77, 056503 (2014).
[2] I. Gross, W.Akhtar et al., Nature, 549, 252 (2017).