| Summary: | The Kerr rotation and Kerr ellipticity of thin films can be measured using an AC magneto-optic Kerr effect (AC-MOKE) system. The longitudinal MOKE measurements were taken for a series of Co2MnSixAl1-x thin films with values of x= 0.00, 0.25, 0.50, 0.75, 1.00. The films were fabricated using ultra high vacuum, pulsed laser deposition (PLD) techniques. The PLD targets were made using conventional arc-melting techniques. Using a Jones matrix analysis, it was shown that the Kerr rotation and Kerr ellipticity can be measured separately using two optical setups by taking advantage of a photoelastic modulator and lock-in techniques.
Co2MnAl and Co2MnSi are both in a class of materials known as Heusler alloys and are predicted to have a high degree of spin polarization. The crystal structure was confirmed as the L21 using powder x-ray diffraction. The lattice constants were shown to be 5.61Å and 5.77 Å for Co2MnSi andCo2MnAl, respectively. For each film, the DC-MOKE, AC-Kerr rotation, and AC- Kerr ellipticity were measured. The DC-MOKE loops were used to estimate the total Kerr rotation. There was no noticeable trend in the values of the total Kerr rotation as calculated using a technique based on Malus law. The Kerr rotation showed a decreasing trend with concentration (x). The sample with x=0.50 was calculated to be the same as the one with x=0.00 value. The Kerr ellipticity also decreased as x was increased. There have been no reports in the literature on direct measurements of the Kerr rotation or ellipticity for Co2MnSixAl1-x for any values of x. The measurements gave values that were comparable to reported calculations and measured values of similar Heusler alloys.
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