Regensburg 2022 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 22: Thin Films: Magnetic Coupling Phenomena / Exchange Bias / Magnetic Anisotropy

MA 22.3: Vortrag

Mittwoch, 7. September 2022, 10:00–10:15, H47

Experimental tests of the accuracy of the reflection matrix description in linear magneto-optics — •Carmen Martín Valderrama, Mikel Quintana, and Andreas Berger — CIC nanoGUNE BRTA, E-20018 Donostia-San Sebastián, Spain

Magneto-Optical (MO) Kerr Effect (MOKE) techniques are frequently utilized to monitor magnetization M reversal, and even its vector information, in a non-destructive way [1]. The assumption is hereby that the Jones-formalism reflection matrix R, including 1^st order MOKE, is given as R= r_sα(m_x)+γ(m_z)
−α(m_x)+γ(m_z)r_p+β(m_y)
, with m_x,y,z being the M components in Cartesian coordinates, r_s and r_p as Fresnel coefficients and α, β and γ being MOKE coefficients for longitudinal, transverse and polar effects. Recently, however, there have been reports of linear MOKE that is independent of a sample’s magnetization [2]. Thus, it is important to verify the above R expression experimentally, which to our knowledge has not been done rigorously. For this, we utilized a sample with uniform M, which can be precisely rotated by an applied field, thus systematically varying the MOKE coefficients, while monitoring all of them simultaneously by means of General MO Ellipsometry. For the pure in-plane magnetization case, for instance, the α vs. β relation will lead to an ellipse equation, α² / α₀² + β² / β₀² = 1, if R is correct. We have confirmed this behavior experimentally with a very high degree of precision. However, we also discovered deviations from it in cases where samples exhibit MO anisotropy. [1] Appl. Phys. Lett. 71, 965 (1997), [2] Phys. Rev. B 102, 140408(R) (2020)