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Nanomagnetism using polarised soft X-rays

Date : Wednesday, November 14th, 2018 16:00 〜 Place : Meeting Room 1 (A636), 6th Floor, ISSP Lecturer : Dr.Sarnjeet S. Dhesi Affiliation : Diamond Light Source Committee Chair : Shik Shin (63380)
e-mail: shin@issp.u-tokyo.ac.jp

Nanomagnetism and spintronics are ubiquitous in our everyday lives so that manipulating magnetic order on ever smaller and faster scales has been a huge endeavour over the past few decades. With the advent of low-emittance third generation synchrotron sources, producing brilliant polarised x-rays, unprecedented site and element-selective insights have been gained into nanomagnetism. At the Diamond Light Source synchrotron, electron microscopy combined with polarised x-ray spectroscopies allows high-resolution imaging of strain and electrical effects on nanomagnetism. In this talk, recent results using PhotoEmission Electron Microscopy (PEEM) combined with X-Ray Absorption Spectroscopy (XAS), X-Ray Magnetic Linear Dichroism (XMLD) and X-Ray Magnetic Circular Dichroism (XMCD) will be presented.
Antiferromagnetic spintronics aims to exploit zero net magnetic moment materials as efficient generators, detectors and transmitters of spin current. PEEM, with magnetic contrast arising from XMLD, has been employed to directly image changes in the antiferromagnetic domain structure of CuMnAs [1] after electrical rotation of the magnetic moments. The XMLD-PEEM images are correlated with in situ Anisotropic Magnetoresistance transport measurements [2,3].
XMLD-PEEM imaging has also been used to directly visualise the antiferromagnetic domain structure of epitaxial (111)-oriented BiFeO3 (BFO) films. Angle-dependent XMLD-PEEM images are combined to reveal a sub-micron network of antiferromagnetic domains (see Figure 1) that are coherently coupled to monoclinic domains. The magnetoelastic coupling is found to stabilise the antiferromagnetic domain structure, providing a possible pathway towards strain-engineering multiferroic domains in (111)-oriented BFO films [4].
Finally, I will explore electrical switching of perpendicular magnetism in Ni films grown on BaTiO3 ferroelectric substrates. XMCD-PEEM maps of the in-plane and out-of-plane magnetization reveal a reversible transformation of the out-of-plane magnetization in the Ni films under voltage control [5].

[1] P. Wadley et al., Nat. Nanotechnol. 13, 362 (2018).
[2] M. J. Grzybowski et al., Phys. Rev. Lett. 118, 057701 (2017).
[3] P. Wadley et al., Science 351, 587 (2016).
[4] N. Waterfield-Price et al., Phys. Rev. Lett. 117, 117601 (2016).
[5] M. Ghidini et al., Adv. Mater. 27, 1460 (2015).

(Published on: Thursday November 1st, 2018)