Kerr angle

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. 

Fig. 14. Polar Kerr angle of Ni in dependence of the strength of s-o interaction (left panel) and exchange splitting (right panel) [35]. The dashed curves give the Kerr rotations evaluated with either the s-o or the exchange coupling scaled by a factor of 0.5, and the dashed-dotted curves those of scaling by a factor of 2.0. The full curves (equivalent in both panels) give the Kerr rotations without any scaling.

Koopmans, B., Koerkamp, M., Rasing, T., and Berg, H. V. D. (1995). Observation of large Kerr angles in the nonlinear optical response from magnetic multilayers. 

Dipole Homents and Kerr Effect. - The structures of two conformers of ethyldifluorophosphane have been determined using a combination of dipole moments and microwave spectroscopy.227 Dipole moments have been used to study the different tuist angles of allenic phosphonates (81),228 and also to deduce the stereochemistry of 1,3,2,5-dioxaboraphosphorinane.22 ... 

Dipole moment studies and molar Kerr constants, in C6Hi2 at 25 °C, have proved of much use in adducing the conformations of acylpyridines (73JCS(P2)l46l)..4-Formylpyridine is planar, but the acetyl group appears to be twisted about 25° from the plane of the pyridine ring in 4-acetylpyridine. The conformation of 4-benzoylpyridine must be defined by two angles 6 and 4> as in (262). The preferred conformation is calculated to be 6 = = 25°, consistent with the result for 4-acetylpyridine. 

In a-pyridyl (32), Kerr constants (66JCS(B)420) support a structure, confirmed by X-ray analysis, with a dihedral angle of 80-83° between the two C=0 planes, and each fragment adopting an N,0-trans orientation. 

In the case of xanthene (8), the moment (1.14 D) is in agreement with the value of 1.15 D for diphenyl ether. On the basis of the Kerr effect, it was postulated that in solution the preferred conformation of xanthene is a folded arrangement in which the dihedral angle between the two aromatic planes is 160 6° <69JCS(B)980). However, the zero moment observed for 2,7-dibromoxanthene is considered to be supportive evidence for a planar xanthene molecule, arising from the equal but opposite directional properties of the resultant moment (1.5 D) of the two C—Br bonds and the moment of xanthene (72MI22205). It should be noted that the latter work is based on a moment of 1.43 D for xanthene, which is substantially higher than other reported values. 

In the solid state, the phenyl nuclei of biphenyl are coplanar (Dhar, 1932 Kitaigorodsky, 1946 Rizvi and Trotter, 1961). Bastiansen (1949) reports that the angle between the rings is 45° in the gas phase as determined by electron diffraction. The conformation of biphenyl in solution is not established (Wheland, 1955). It has been argued to be coplanar on the basis of the Kerr constant (Chau et al., 1959). Recent observations of the electronic spectrum of biphenyl and certain derivatives in the solid, liquid, and vapor states were interpreted as indicative of a 20° deviation from coplanarity in solution (Suzuki, 1959). 

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