Abstract
In conventional Kerr and Faraday microscopy, the sample is illuminated with plane-polarized light, and a magnetic domain contrast is generated by an analyzer making use of the Kerr or Faraday rotation. Here, we demonstrate possibilities of analyzer-free magneto-optical microscopy based on magnetization-dependent intensity modulations of the light. (i) The transverse Kerr effect can be applied for in-plane magnetized material, as demonstrated for an FeSi sheet. (ii) Illuminating that sample with circularly polarized light leads to a domain contrast with a different symmetry from the conventional Kerr contrast. (iii) Circular polarization can also be used for perpendicularly magnetized material, as demonstrated for garnet and ultrathin CoFeB films. (iv) Plane-polarized light at a specific angle can be employed for both in-plane and perpendicular media. (v) Perpendicular light incidence leads to a domain contrast on in-plane materials that is quadratic in the magnetization and to a domain boundary contrast. (vi) Domain contrast can even be obtained without a polarizer. In cases (ii) and (iii), the contrast is generated by magnetic circular dichroism (i.e., differential absorption of left- and right-circularly polarized light induced by magnetization components along the direction of light propagation), while magnetic linear dichroism (differential absorption of linearly polarized light induced by magnetization components transverse to propagation) is responsible for the contrast in case (v). The domain–boundary contrast is due to the magneto-optical gradient effect. A domain–boundary contrast can also arise by interference of phase-shifted magneto-optical amplitudes. An explanation of these contrast phenomena is provided in terms of Maxwell–Fresnel theory.
Highlights
Numerous applications of the magneto-optical (MO) Kerr effect (MOKE) are well established, including optical magnetometry[1] and magnetic domain imaging in wide-field[2] polarization microscopes[3,4,5] and by laser-scanning microscopy.[6]
In conventional Kerr and Faraday microscopy, the sample is illuminated with plane-polarized light, and a magnetic domain contrast is generated by an analyzer making use of the Kerr or Faraday rotation
We demonstrate possibilities of analyzer-free magneto-optical microscopy based on magnetization-dependent intensity modulations of the light. (i) The transverse Kerr effect can be applied for in-plane magnetized material, as demonstrated for an FeSi sheet. (ii) Illuminating that sample with circularly polarized light leads to a domain contrast with a different symmetry from the conventional Kerr contrast. (iii) Circular polarization can be used for perpendicularly magnetized material, as demonstrated for garnet and ultrathin CoFeB films. (iv) Plane-polarized light at a specific angle can be employed for both in-plane and perpendicular media. (v) Perpendicular light incidence leads to a domain contrast on in-plane materials that is quadratic in the magnetization and to a domain boundary contrast. (vi) Domain contrast can even be obtained without a polarizer
Summary
Numerous applications of the magneto-optical (MO) Kerr effect (MOKE) are well established, including optical magnetometry[1] and magnetic domain imaging in wide-field[2] polarization microscopes[3,4,5] and by laser-scanning microscopy.[6]. Rotation-based Kerr, Faraday, and Voigt microscopy have been (almost) exclusively employed for domain imaging in the visible frequency regime.[3,4,5] A recent investigation[18] on ultrathin magnetic films showed that antireflection coatings could significantly enhance the MO rotation and further found that a MO contrast could even be detected by illuminating the sample with left- and rightcircularly polarized (LCP and RCP) light rather than by planepolarized light, making use of the MCD effect The latter contrast was enhanced by the extreme antireflection coating used in that work, but it indicates the possibility of magnetic domain imaging without the need for an analyzer, which would not have any effect on a circularly polarized wave anyway. We refer to largely forgotten, 60-year-old research that already pointed out the possibility of magneto-optical imaging without the need of a polarizer and analyzer but, based on dark-field optical microscopy.[26]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
