Quadratic magneto-optical Kerr effect in Co2MnSi

Abstract

Quadratic magneto-optical Kerr effects (QMOKE) are investigated in epitaxial Co 2 MnSi thin films as a function of the post-deposition annealing temperature. We determine the amplitude of the QMOKE signal for different annealing temperatures, which provide various degrees of L2 1 crystal ordering, as manifested by X-ray diffraction. We observe that QMOKE is significantly present only when the L2 1 ordering phase is also present, and that the QMOKE signal increases with the higher degree of L2 1 ordering. Additionally, we notice that the linear magneto-optical Kerr effect (LMOKE) decreases with higher annealing temperature. A comparison of the linear and quadratic MOKE contributions shows the amplitudes are of similar magnitude. From these results, we conclude that the presence of QMOKE is linked to the higher degree of L2 1 ordering in Co 2 MnSi.

Co2FeAl thin films grown on MgO substrates: Correlation between static, dynamic, and structural properties

“…As the thickness decreases the amplitudes and the offset decrease, suggesting that the chemical order progressively changes from the B2 to the A2 phase, as discussed above. Moreover, the amplitudes and offset values of CFA are comparable to those measured for Co 2 MnSi, which presents the L2 1 phase [28]. The TBIIST results are discussed in the following section, in order to allow for a comparison with the data derived from the FMR study of the dynamic properties.…”

Quantitative study of the quadratic magneto-optical Kerr effects in Fe films

“…1(b). To quantify the values of LT Φ and TT Φ , the measured ( ) [4][5][6]15], the QMOKE contributions were separated by the eight-field method, which assumes the magnetizations lie along the field directions, i.e. m H φ φ = ; this assumption could be questionable if the external field is not strong enough compared with the magnetic anisotropy.…”

“…Most applications describe the magnetization with the normalized Kerr angle based on the first-order linear magneto-optical Kerr effect (LMOKE), neglecting the higher-order quadratic magneto-optical Kerr effect (QMOKE). However, the QMOKE analysis is important in the following considerations: (i) for materials with a huge QMOKE [4][5][6], this higher-order contribution must be considered to quantitatively calibrate the magnetization measurements; (ii) because the quadratic magneto-optical (MO) coupling is caused by second-order spin-orbit coupling terms [4], the MO coupling parameters related to the QMOKE can be used as a probe for fundamental electronic interactions in ferromagnetic materials; and (iii) optical effects quadratic in magnetization have recently been determined to be important, including magnetization-dependent second-harmonic generation [7], the quadratic X-ray magneto-optical effect [8], and the closely related X-ray Voigt effect [9]. A systematic study of the QMOKE therefore can provide a good reference for the study of other related effects.…”

Ultrafast magnetization dynamics in Co-based Heusler compounds with tuned chemical ordering

“…We further observe that the QMOKE signal of the films strongly increases with annealing temperature (see figure 3(c)), which is also linked to the appearance of the L2 1 phase. In fact, according to [59,60], with higher disorder the optical transitions responsible for the QMOKE are broadened and no effect can be observed, while for higher crystal order the well defined symmetry and spin-orbit coupling can lead to a large QMOKE signal.…”