A high-resolution combined scanning laser and widefield polarizing microscope for imaging at temperatures from 4 K to 300 K

Abstract

Polarized light microscopy, as a contrast-enhancing technique for optically anisotropic materials, is a method well suited for the investigation of a wide variety of effects in solid-state physics, as for example birefringence in crystals or the magneto-optical Kerr effect (MOKE). We present a microscopy setup that combines a widefield microscope and a confocal scanning laser microscope with polarization-sensitive detectors. By using a high numerical aperture objective, a spatial resolution of about 240 nm at a wavelength of 405 nm is achieved. The sample is mounted on a 4 He continuous flow cryostat providing a temperature range between 4 K and 300 K, and electromagnets are used to apply magnetic fields of up to 800 mT with variable in-plane orientation and 20 mT with out-of-plane orientation. Typical applications of the polarizing microscope are the imaging of the in-plane and out-of-plane magnetization via the longitudinal and polar MOKE, imaging of magnetic flux structures in superconductors covered with a magneto-optical indicator film via Faraday effect or imaging of structural features, such as twin-walls in tetragonal SrTiO 3 . The scanning laser microscope furthermore offers the possibility to gain local information on electric transport properties of a sample by detecting the beam-induced voltage change across a current-biased sample. This combination of magnetic, structural and electric imaging capabilities makes the microscope a viable tool for research in the fields of oxide electronics, spintronics, magnetism and superconductivity.

Quantitative magneto-optical investigation of superconductor/ferromagnet hybrid structures

“…Let us start by introducing the experimental setup used for acquiring magneto-optical images. MOI is a magnetic field mapping microscopy technique based on the Faraday effect, where the direction of polarization of a light beam is rotated proportionally to the local magnetic field [1,2,26,30]. This effect is strongest in purposely designed indicator films, placed on top of the sample under study.…”

Imaging of Electrothermal Filament Formation in a Mott Insulator

“…We used an wide-field optical microscope [32] with the device mounted in a vacuum, in a continuous He gas-flow cryostat. The microscope has a spatial resolution of 0.5 µm.…”

A low-temperature Kerr effect microscope for the simultaneous magneto-optic and magneto-transport study of magnetic topological insulators

“…It is possible to further develop a Kerr microscope with combined scanning and wide-field configurations to utilise the virtues of both, and a good example can be found in Ref. [47].…”