Engineering The Polar Magneto-Optical Kerr Effect In Strongly Strained L1(0)-Mnal Films

We report the engineering of the polar magnetooptical (MO) Kerr effect in perpendicularly magnetized L1(0)-MnAl epitaxial films with remarkably tuned magnetization, strain, and structural disorder by varying substrate temperature (T-s) during molecular-beam epitaxy growth. The Kerr rotation was enhanced by a factor of up to 5 with T-s increasing from 150 to 350 degrees C as a direct consequence of the improvement of the magnetization. A similar remarkable tuning effect was also observed on the Kerr ellipticity and the magnitude of the complex Kerr angle, while the phase of the complex Kerr angle appears to be independent of the magnetization. The combination of the good semiconductor compatibility, the moderate coercivity of 0.3-8.2 kOe, the tunable polar MO Kerr effect of up to similar to 0.034 degrees, and giant spin precession frequencies of up to similar to 180 GHz makes L1(0)-MnAl films a very interesting MO material. Our results give insights into both the microscopic mechanisms of the MO Kerr effect in L1(0)-MnAl alloys and their scientific and technological application potential in the emerging spintronics and ultrafast MO modulators.