Ellipsometric Characterization for Multilayers Containing Magneto-Optic TbFeCo Films

1987 ◽  
Vol 103 ◽  
Author(s):  
M. Ruane ◽  
A. Jain
Keyword(s):  
Optical Activity ◽  
Optical Signal ◽  
Optically Active ◽  
Index Of Refraction ◽  
Dielectric Tensor ◽  
Angle Of Incidence ◽  
Multilayered Structures ◽  
Kerr Rotation ◽  
Ellipsometric Characterization ◽  
Sputter Deposited

ABSTRACTMultilayered structures containing sputter-deposited films of amorphous TbFeCo can exhibit magneto-optical Kerr rotation and are leading candidates for erasable optical storage media. Ellipsometric characterization of optically active multilayered media is desirable during media development, testing and production, but traditional ellipsometry does not account for the presence of optical activity. A novel ellipsometer is described that can characterize both the dielectric overcoat and the optically active layers. Reflectivity measurements are collected for different incident angles and polarizations using a differential detector while the magnetic reversibility of the active film layer is exploited to enhance the magneto-optical signal from the TbFeCo. A multilayer film model is used to process observations and estimate media characteristics. The model explicitly accounts for the optical activity of the TbFeCo layer, and is parameterized in terms of the index of refraction and thickness of the overcoat, and the real and imaginary parts of the elements of the dielectric tensor of the active layer.A series of TbFeCo films with varying composition, rf-sputter deposited on quartz substrates with Al2O3 dielectric protective overcoats, is characterized. Both Tb-rich and Fe-rich samples were deposited, with room temperature coercivities ranging from 1.6kOe to about 4kOe, and film-side Kerr rotations between 21 minutes and 28 minutes. Reflectivity data versus angle of incidence, and estimated dielectric tensor elements for the TbFeCo layers are presented. A standard figure of merit, based on the off-diagonal tensor elements, is used to compare competing media in terms of their optimal performance in a multilayered structure.

High-resolution TEM of Cr-Gd and Co-Gd multilayers

1992 ◽  
Vol 50 (1) ◽  
pp. 200-201
Author(s):  
Gerardo A. Bertero
Keyword(s):  
Heat Of Mixing ◽  
Magnetic Media ◽  
Multilayered Structures ◽  
Kerr Rotation ◽  
High Resolution Tem ◽  
Large Heat ◽  
Optical Applications ◽  
Sputter Deposited ◽  
Magneto Optic

Thin film multilayered structures have assumed significant technological importance. In particular, several have proven adequate for magneto-optic recording applications in which vertical magnetization, large coercivities and a large Kerr rotation effect are needed. In this regard, Co-Gd and Cr-Gd, among others, are candidate systems and specifically Gd-Co has already been used with some success.In the present work, HRTEM was performed on sputter-deposited Cr-Gd and Co-Gd multilayers. These two systems are expected to show contrasting behavior which may affect the long term magneto-optic performance of the multilayer. Cr and Gd are almost totally immiscible, suggesting a large positive heat of mixing. Conversely, Co and Gd form a large number of intermetallic phases and show a deep eutectic at 60 at.% Gd indicating a negative, and possibly large, heat of mixing. Thus, a tendency for intermixing and solid state amorphization is expected for the Co-Gd system and not so for Cr-Gd. These considerations may be of importance since thermal stability is required for magneto-optical applications where the magnetic media is subjected to local thermal cycling during the magnetic writing process.

Dielectric Tensor Characterization for Overcoated Amorphous TbFe Alloys

1986 ◽  
Vol 80 ◽  
Author(s):  
M. Ruane ◽  
A. Jain ◽  
R. Rosenvold ◽  
M. Mansuripur
Keyword(s):  
Protective Layer ◽  
Estimation Algorithm ◽  
Optical Signal ◽  
Dielectric Tensor ◽  
Amorphous Thin Films ◽  
Sputter Deposited ◽  
Reflectivity Data ◽  
Quartz Substrates ◽  
Optical Behavior ◽  
Made In

AbstractAmorphous thin films of TbFe. sputter-deposited on quartz substrates with compositions supporting polar Kerr magneto-optical behavior, and overcoated with a transparent protective layer, are studied to determine their dielectric tensor elements. Refleetivity measurements over a range of angles of incidence are made in an apparatus that corrects for the overcoat layer and exploits magnetization reversal to enhance the measurement of r⊥, the complex reflectivity associated with the magneto-optical signal. Conventional Fresnel reflectivities are also found. The theoretical model for reflectivities from a thick film magneto-optical medium at oblique incidenci is developed and used within a Levenberg-Marquardt nonlinear estimation algorithm to estimate sequentially the dielectric tensor elements, considering their widely varying magnitudes and sensitivities to errors in reflectivity data. The interpretation of the dielectric elements in terms of magneto-optical performance and structural perpendicular anisotropy is discussed.

X. On the action of the second surfaces of transparent plates upon light

1830 ◽  
Vol 120 ◽  
pp. 145-152 ◽  
Keyword(s):  
Index Of Refraction ◽  
Angle Of Incidence ◽  
Remarkable Result ◽  
The Law ◽  
Polarization Of Light

In a paper on the Polarization of Light by Reflexion, published in the Philosophical Transactions for 1815, I showed that the Law of the Tangents was rigorously true for the second surfaces of transparent bodies, provided that the sine of the angle of incidence was less than the reciprocal of the index of refraction. The action of the second surfaces of plates at angles of incidence different from the maximum polarizing angle, was studied by M. Arago, who conducted his experiments in the following manner. “With respect to this phænomenon,” says M. Arago, “a remarkable result of experiment may here be noticed; that is, that in every possible inclination A = A'.

On the syntheses and the optical properties of optically active 2-pyrazoline compounds

1979 ◽  
Vol 57 (3) ◽  
pp. 360-366 ◽  
Author(s):  
Makoto Mukai ◽  
Takashi Miura ◽  
Masahiro Nanbu ◽  
Toshinobu Yoneda ◽  
Yohji Shindo
Keyword(s):  
Optical Properties ◽  
Optical Activity ◽  
Optically Active ◽  
Spectroscopic Techniques ◽  
Considerable Influence ◽  
Pyrazoline Ring

Optically active 2-pyrazolines were synthesized and their optical properties were studied using various spectroscopic techniques to investigate the effects of substituents at the 3 and 5 positions of the 2-pyrazoline ring on their optical activity. It was found that in the case of 5-substituted-1,3-diphenyl-2-pyrazoline derivatives, the substituent at the 5 position has considerable influence on the optical activity, whereas in 3-substituted-1,5-diphenyl-2-pyrazoline derivatives, the substituent at the 3 position has no such influence.

scholarly journals Enhanced gyrotropic birefringence and natural optical activity on electromagnon resonance in a helimagnet

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
S. Iguchi ◽  
R. Masuda ◽  
S. Seki ◽  
Y. Tokura ◽  
Y. Takahashi
Keyword(s):  
Symmetry Breaking ◽  
Spontaneous Symmetry Breaking ◽  
Optical Activity ◽  
Optical Rotation ◽  
Magnetoelectric Coupling ◽  
Optically Active ◽  
Crystalline Solid ◽  
Spin Order ◽  
Active Devices ◽  
Principal Axes

AbstractSpontaneous symmetry breaking in crystalline solid often produces exotic nonreciprocal phenomena. As one such example, the unconventional optical rotation with nonreciprocity, which is termed gyrotropic birefringence, is expected to emerge from the magnetoelectric coupling. However, the fundamental nature of gyrotropic birefringence remains to be examined. Here w`e demonstrate the gyrotropic birefringence enhanced by the dynamical magnetoelectric coupling on the electrically active magnon resonance, i.e. electromagnon, in a multiferroic helimagnet. The helical spin order having both polarity and chirality is found to cause the giant gyrotropic birefringence in addition to the conventional gyrotropy, i.e. natural optical activity. It is demonstrated that the optical rotation of gyrotropic birefringence can be viewed as the nonreciprocal rotation of the optical principal axes, while the crystallographic and magnetic anisotropies are intact. The independent control of the nonreciprocal linear (gyrotropic birefringence) and circular (natural optical activity) birefringence/dichroism paves a way for the optically active devices.

Optical activity and enantiomorphism

2004 ◽  
Author(s):  
Robert E. Newnham
Keyword(s):  
Optical Activity ◽  
Polarized Light ◽  
Polarization Vector ◽  
Optically Active ◽  
Crystal Thickness ◽  
Helical Structures ◽  
Active Materials ◽  
Circularly Polarized ◽  
Space Groups ◽  
Polarized Waves

When plane-polarized light enters a crystal it divides into right- and lefthanded circularly polarized waves. If the crystal possesses handedness, the two waves travel with different speeds, and are soon out of phase. On leaving the crystal, the circularly polarized waves recombine to form a plane polarized wave, but with the plane of polarization rotated through an angle αt. The crystal thickness t is in mm, and α is the optical activity coefficient expressed in degrees/mm. The polarization vector of the combined wave can be visualized as a helix, turning α ◦/mm path length in the optically-active medium. Because of the low symmetry of a helix, optical activity is not observed in many high symmetry crystals. Point groups possessing a center of symmetry are inactive. In relating α to crystal chemistry it is convenient to divide optically-active materials into two categories: Those which retain optical activity in liquid form, and those which do not. It has long been known that optically-active solutions crystallize to give optically-active solids. This follows from the fact that molecules lacking mirror or inversion symmetry can never crystallize in a pattern containing such symmetry elements. Thus one way of obtaining optically-active materials is to begin with optically-active molecules, as in Rochelle salt, tartaric acid and cane sugar. Few of these crystals are very stable, however, and the optical activity coefficients are usually small, typically 2◦/mm. The same is true of many inorganic solids, though they are seldom optically active in the liquid state. For NaClO3 and MgSO4·7H2O, α is about 3◦/mm. Quartz and selenium, however, have coefficients an order of magnitude larger, showing the importance of helical structures to optical activity. Both compounds crystallize as right- and left-handed forms in space groups P312 and P322, with helices spiraling around the trigonal screw axes. Quartz contains nearly regular SiO4 tetrahedra with Si–O distances of 1.61 Å. Levorotatory quartz belongs to space group P312 and contains right-handed helices; enantiomorphic dextrorotatory quartz crystallizes in P322. Trigonal selenium also contains helical chains.

Methacrylic polymers bearing side-chain permanent dipole azobenzene chromophores spaced from the main chain by chiral moieties, 3 a Synthesis and chiroptical properties of the homopolymer of (R)-3-methacryloyloxy-1-(4’-nitro-4-azobenzene)- pyrrolidine and of copolymers with the enantiomeric monomer (S)-3-methacryloyloxy-1-(4’-nitro-4-azobenzene)- pyrrolidine

e-Polymers ◽  
2003 ◽  
Vol 3 (1) ◽  
Author(s):  
Luigi Angiolini ◽  
Loris Giorgini ◽  
Elisabetta Salatelli
Keyword(s):  
Radical Polymerization ◽  
Optical Activity ◽  
Main Chain ◽  
Optically Active ◽  
Side Chain ◽  
Chiroptical Properties

Abstract The optically active photochromic homopolymer deriving from radical polymerization of the monomer (R)-3-methacryloyloxy-1-(4’-nitro-4-azobenzene)- pyrrolidine, containing a chiral group of one prevailing configuration interposed between the methacrylic moiety and the photochromic azoaromatic chromophore, has been synthesized and characterized. Copolymers with the enantiomeric monomer (S)-3-methacryloyloxy-1-(4’-nitro-4-azobenzene)pyrrolidine have also been prepared in order to evaluate the effect on the overall optical activity of side chain chiral groups of opposite configuration in various ratios. The spectroscopic and chiroptical properties in solution of the polymeric derivatives have been assessed.

Dynamic optical activity induction in the N-alkyl-N′-trityl ureas and thioureas

2019 ◽  
Vol 17 (33) ◽  
pp. 7782-7793 ◽  
Author(s):  
Natalia Prusinowska ◽  
Agnieszka Czapik ◽  
Martika Wojciechowska ◽  
Marcin Kwit
Keyword(s):  
Hydrogen Bonding ◽  
Optical Activity ◽  
Optically Active ◽  
Thiourea Derivatives ◽  
Hydrogen Bonding Network ◽  
Activity Induction

Stereodynamic trityl group, utilized as a reporter of chirality, hampers hydrogen bonding network in optically active urea and thiourea derivatives.

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