Polar Kerr effect

Fig. 8. Principle of the magnetooptical read-out of domain patterns by the polar Kerr effect. The polarisation plane of the incoming laser beam is rotated clock- or counterclockwise according to the orientation (up or down) of the magnetic moments.

From the write and read process sketched so far, some requirements for MO media can be derived (/) a high perpendicular, uniaxial magnetic anisotropy K in order to enable readout with the polar Kerr effect (2) a magnetoopticady active layer with a sufficient figure of merit R 0- where R is the reflectivity and the Kerr angle (T) a Curie temperature between 400 and 600 K, the lower limit to enable stable domains at room temperature and the upper limit because of the limited laser power for writing. 

Figure 38. XRD pattem(a) and hysteresis loop(b) of FePt C double-layered media. Loop measured by polar-Kerr Effect at room temperature.

Fig. 1. Schematic representation of the three different types of Kerr effect configurations (a) Polar Kerr effect, (b) Longitudinal Kerr effect, (c) Equatorial Kerr effect.

Voloshinskaya and Fedorov (1973) measured the equatorial Kerr effect and the polar Kerr effect in Fe-V alloys. Results of the Kerr rotation measurements are shown in fig. 12. It can be seen that increasing the V concentration strongly reduces the absolute value of the Kerr rotation. This is the case in particular in the region of the first minimum at 1.2 eV ( 1 (im). Unfortunately, the authors did not perform measurements on pure Fe metal themselves. Included in the figure are results of Afanas yeva and Kirillova et al. (1967) and Krinchik and Artem ev (1968) obtained... 

The complex polar Kerr effect consists of both the rotation of polarization plane and the appearance of the ellipticity if a linearly polarized light reflects from a sample surface and the sample is magnetized normally to this surface (Figure 7.6a). If the light falls from the vacuum perpendicularly on the sample... 

MO Kerr effects are used to observe the domain structure of opaque materials. If the magnetization vector is perpendicular to the sample plane, then the polar Kerr effect is utilized. If the magnetization lies in the sample plane, then structure images can be obtained either in the longitudinal geometry with polarizers or in the transverse geometry without polarizers. 

The effect of M on the reflected light intensity is known as the Kerr effect. The polar Kerr effect refers to a situation in which the sample has a component of M normal to the surface and normal incidence illumination is used. The longitudinal Kerr effect is used when M is parallel to the surface and the illumination is oblique. 

In the case of the polar Kerr effect (case a in fig. 57) the amplitude r of the reflected light is given by... 

C. Liu, E.R. Moog, S.D. Bader, Polar Kerr-effect observation of perpendicular surface anisotropy for ultrathin fee Fe grown on Cu(lOO). Phys. Rev. Lett. (23), 2422-2425... 

Amongst the RBO3 compounds containing a transition metal B ion most of the optical work has been done on the orthoferrites. In typical examples of this type optical studies have been made on ErFeOs (Wood et al., 1969) and TmFe03 (Malozemoff, 1971). In addition to the absorption lines due to the rare earth ions, broad bands related to the crystal field absorption of the Fe ion are present. Another optical property studied for the orthoferrites is the polar Kerr effect... 

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