Universal description of surface magnetism via magnetoelectric effects

Date

Jan 16, 2025

Time

1:00 PM - 3:00 PM

Speaker

Andrea Urru

Affiliation

Rutgers University

Series

TUD nanoSeminar

Language

en

Main Topic

Physik

Other Topics

Physik

Host

Arezoo Dianat

Description

Due to their reduced symmetry, surfaces often host physical phenomena that are absent in the
 corresponding bulk material. Of particular interest for spintronics applications is the case of
 surfaces showing a non-vanishing magnetic dipole per unit area, named “surface magnetization”
 [1-2], which can occur despite the corresponding bulk being a perfectly compensated
 antiferromagnet with zero net magnetization. Such surface magnetization underlies intriguing
 physical phenomena like interfacial magnetic coupling, and can be used as a readout method of
 antiferromagnetic domains [3-4].
 In this talk, I will first introduce a classification scheme based on whether the surface of interest is
 magnetically compensated or uncompensated if the bulk magnetic order is retained at the
 surface. Then, I will show how surface magnetization can be understood in terms of bulk
 magnetoelectric effects, whereby an applied electric field induces a net magnetization. The link
 between a bulk magnetoelectric response and surface magnetization is intuitively expected by the
 fact that the abrupt termination of a bulk to create a surface generates also an effective electric
 field at the surface. This bulk-to-boundary correspondence serves as the ground for a universal
 description of surface magnetization in antiferromagnets, which has been lacking thus far [5].
 Finally, I will use density functional calculations to illustrate that nominally compensated surfaces
 in Cr2 O3 and centrosymmetric FeF 2 develop a finite magnetization at the surface, in agreement
 with our predictions based on the corresponding bulk magnetoelectric response.
 [1] K. D. Belashchenko, Phys. Rev. Lett. 105, 147204 (2010)
 [2] M. S. Wornle et al., Phys. Rev. B 103, 094426 (2021)
 [3] N. Hedrich et al., Nat. Phys. 17, 574 (2021)
 [4] J. Nogues and I. K. Schuller, J. Magn. Magn. Mater. 192, 203 (1999).
 [5] S. F. Weber, A. Urru, S. Bhowal, C. Ederer, and N. A. Spaldin, Phys. Rev. X 14, 021033 (2024).

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Last modified: Nov 21, 2024, 7:40:28 AM