A systematic study of quantum efficiencies and lifetimes has been carried out for the visible fluorescences of Pr3+ in single-crystal LaF3. An analysis of the results as a function of Pr3+ concentration is given in terms of a two-site model in which a Pr3+ ion can either be in an isolated site or in a site where it is coupled to other impurity ions. This model leads to ion—ion interaction ranges varying from ∼5 Å (nearest neighbor) to ∼12 Å depending on the fluorescent level studied. Throughout this range of interaction lengths, Dexter's model of electrostatic ion—ion interaction shows that the dominant contribution comes from the quadrupole—quadrupole term. Temperature effects in the interaction are consistent with the lack of exact resonance between the electronic levels. It appears that the lattice can readily absorb excess energy up to ∼1000 cm−1.
A set of samples doped with a second rare earth (Ce3+, Nd3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+) has demonstrated the existence of selection rules for ion—ion interaction in addition to energy-matching requirements. The system 0.5% Pr3+: x% Ce3+ has been studied in more detail.
Magnetic resonance technique may successfully be applied to determine some basic parameters such as g-factor, magnetization Ms or anisotropy energy constant Kui n t h i n m a g n e t i c f r l m s . T h e s e p a r a m e t e r s a r e o b t a i n e d f r o m a ferromagnetic resonance experiment when uniform precession of M$st a k e s place. From spin-wave resonance one may extract very valuable information on the exchange constant A or the surface conditions characterized by the surface anisotropy energy (or pinning parameters p). In fact, it is only spin-wave resonance or similar techniques which allow for measurements of A, p or the coupling constant Kc between ferromagnetic sublayers in multilayered structure. The magnetic phase diagram, temperature dependence of the spin-waves stiffness constant, and the anisotropy energy constant may also be listed as 1ess common examples of spin-wave resonance technique application for the investigation of thin films. This paper presents a theoretical approach to typical examples of experimental results and their interpretation from spin-wave resonance measurements.
A magneto-optic Kerr effect system for the measurement of magnetization in thin ferromagnetic layers based on a photoelastic modulator is described. The use of a quarter wave plate allows light with a variable polarization incident on the sample to be used. The polarization of the light as it passes through the system is treated algebraically using a matrix approach. A procedure for determining both the magneto-optic (MO) rotation presented by the sample and the traditional ellipsometric parameters is described, the consistency of the solutions being demonstrated by experiment. Typical MO rotation versus thickness curves for thin films of Permalloy (Ni79Fe21) deposited on glass for both the longitudinal and transverse field configurations are presented. These results demonstrate that the magnitude and sign (in the transverse case) of the MO rotation is strongly dependent on thickness for films thinner than 200 Å.
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