Search for: All records

We present a magneto-optical Kerr effect (MOKE) spectrometer based on a modified Martin–Puplett interferometer, utilizing continuous wave sub-THz low-power radiation in a broad frequency range. This spectrometer is capable of measuring the frequency dependence of the MOKE response function, both the Kerr rotation and ellipticity, simultaneously, with accuracy limited by a sub-milliradian threshold, without the need for a reference measurement. The instrument’s versatility allows it to be coupled to a cryostat with optical windows, enabling studies of a variety of quantum materials such as unconventional superconductors, two-dimensional electron gas systems, quantum magnets, and other systems showing optical Hall response at sub-Kelvin temperatures and in high magnetic fields. We demonstrate the functionality of the MOKE spectrometer using an undoped InSb wafer as a test sample. 

Abstract We present Raman-scattering results for three materials, CeB 6 , TbInO 3 , and YbRu 2 Ge 2 , to illustrate the essential aspects of crystal-field (CF) excitations and quadrupolar fluctuations of 4 f -electron systems. For CF excitations, we illustrate how the 4 f orbits are split by spin-orbit coupling and CF potential by presenting spectra for inter- and intra-multiplet excitations over a large energy range. We discuss identification of the CF ground state and establishment of low-energy CF level scheme from the symmetry and energy of measured CF excitations. In addition, we demonstrate that the CF linewidth is a sensitive probe of electron correlation by virtue of self-energy effect. For quadrupolar fluctuations, we discuss both ferroquadrupolar (FQ) and antiferroquadrupolar (AFQ) cases. Long-wavelength quadrupolar fluctuations of the same symmetry as the FQ order parameter persists well above the transition temperature, from which the strength of electronic intersite quadrupolar interaction can be evaluated. The tendency towards AFQ ordering induces ferromagnetic correlation between neighboring 4 f -ion sites, leading to long-wavelength magnetic fluctuations.