Developments in surface magneto-optical Kerr effect setup for ultrahigh vacuum analysis of magnetic ultrathin films

Abstract

We describe a surface magneto-optical Kerr effect ͑SMOKE͒ setup designed to study the magnetic properties of ultrathin films in ultrahigh vacuum ͑UHV͒. As in earlier systems, a crossed-poles electromagnet is used, which allows measurements in the longitudinal or polar configurations to be carried out without displacing the sample or changing the optical path. The poles are mounted in-vacuum, while the coils and yoke are mounted externally to obtain a higher magnetic field ͑ϳ2.8 kOe͒. The width of the gap between the poles can be adjusted depending on the size of the sample. The performance of the instrument is demonstrated by measurements of the paramagnetic-ferromagnetic phase transition in a 2 ML Fe film grown on the Mo͑110͒ surface. Epitaxial ultrathin films exhibit magnetic properties due to the reduced dimensionality, the presence of the mismatchinduced strain and the interaction with the substrate. There is also a strong correlation between the film morphology and properties such as the Curie temperature T c and the easy axis of magnetization. The surface magneto-optical Kerr effect ͑SMOKE͒ is a powerful method for probing the magnetic properties of these ultrathin film systems.

Analytic description and optimization of magneto-optical Kerr setups with photoelastic modulation

“…To detect changes in the polarization of a linearly polarized incident beam after reflection on the magnetic sample, some schemes rely on a simple polarizer followed by a photodetector. 10, [25][26][27] Others exploit polarizing beamsplitters to separate the reflected polarization components and subtract them. 28,29 Many experimental setups also include a modulator and a lock-in amplifier to improve the SNR, 24,30,31 which is essential because Kerr effects are typically very small.…”

A UHV MOKE magnetometer complementing XMCD-PEEM at the Elettra Synchrotron

“…Microscopic imaging applications using the Kerr effect have also been a prolific approach in magnetism research, with micrometre lateral resolution due to the diffraction limit at visible wavelengths (Freeman et al, 1998;Ishibashi et al, 2006;Srivastava et al, 2018). Most notably, surface MOKE enables the sensitivity to a single atomic layer to be reached, which makes it highly suitable for the study of ultra-thin magnetic films (Bader et al, 1986;Qiu & Bader, 2000;Usov et al, 2005). Ultra-high vacuum (UHV) operation is also feasible, although hampered by space constraints and the difficulty of operating strong electromagnets in a vacuum.…”

Scanning heterodyne Kerr-effect microscope for imaging of magnetic tracks

“…Traditionally, either the homodyne bichannel scheme was being used to investigate the Kerr effect 7,8,[18][19][20] or the method of direct detection of weak orthogonally polarized component. 1,13,[21][22][23] Recently a new technique based on heterodyning of cross-polarized components of Zeeman laser was introduced. 24 Advantages of this technique over both the homodyne and direct detection techniques include higher sensitivity and lower noise in the output signal.…”