The magnetic susceptibilities of the monophosphides of V, Cr, Fe, and Co have been measured from 4.2°K to room temperature. They were all found to be weakly paramagnetic. The previously reported metamagnetic transition in the MnP was confirmed, whereas none of the other compounds exhibited a magnetic transition. The relative magnitudes of the susceptibilities are shown to be consistent with a band structure proposed by Goodenough in which Mott's suggestion of a critical distance for localized or itinerant electron states is used. The uniqueness of magnetism in MnP is shown to result from the intersection of the Fermi level with a localized electron state before exchange splitting occurs. The nuclear magnetic resonance frequencies of P 31 and Co 69 were also measured and indicated some overlapping of the d band with the conduction band.
The growth and magnetic properties of GdIG films grown by chemical vapor deposition on YIG and GdGaG substrates is described. Various aspects of the deposition technique including the design of a concentric tube reactor, hydrodynamics of the gas flow, substrates, and deposition parameters are discussed in detail. GdIG films have been grown at rates as high as 16 μ/h. They are epitaxial and are of the same orientation as the substrate. The films are strained because of mismatch between the film and substrate. A Faraday effect hysteresigraph has been used to measure the coercive force and the compensation temperature. The remanence has been measured as a function of temperature from −40° to 60°C and has been correlated with strains in the film. Diffusion has been observed between the film and substrate. This can be minimized by increased growth rates and by preheating substrates.
The conventional dynamical equations of wall motion are modified by a phenomenological nonlinear damping factor to describe the nonlinearity and velocity saturation observed in some bubble materials. We show that under certain restrictive but common conditions the solution of the resultant nonlinear differential equation can be obtained from the conventional linear solution by the simple transformation t → t ± x/v, where v is the saturation velocity. The conditions for this solution are (a) that the inertial terms are negligible and (b) that the motion is such that the velocity does not change sign. Solutions of the modified dynamical equation are compared with measurements of step-function wall response and of bubble collapse in Y2.4Eu0.6Fe3.8Ga1.2O12, and it is shown that the measurements are consistently and adequately described by the nonlinear dynamical equation. The nonlinear damping also modifies the equation describing bubble velocity in gradient fields, and it is shown that the modified equation is consistent with propagation data.
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