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Magnetic anisotropies of molecular-beam-epitaxy-grown fcc Co͑110͒ films on Cu͑110͒ single-crystal substrates have been determined by using Brillouin light scattering and have been correlated with the structural properties determined by low-energy electron diffraction and scanning tunneling microscopy ͑STM͒. Three regimes of film growth and associated anisotropy behavior are identified: coherent growth in the Co film thickness regime of up to 13 Å, in-plane anisotropic strain relaxation between 13 and about 50 Å and in-plane isotropic strain relaxation above 50 Å. The structural origin of the transition between anisotropic and isotropic strain relaxation was studied using STM. In the regime of anisotropic strain relaxation long Co stripes with a preferential ͓110͔-orientation are observed, which in the isotropic strain relaxation regime are interrupted in the perpendicular in-plane direction to form isotropic islands. In the Co film thickness regime below 50 Å an unexpected suppression of the magnetocrystalline anisotropy contribution is observed. Symmetry reflections based on a crystal-field formalism and discussed within the context of band theory, which explicitly takes tetragonal misfit strains into account, reproduce the experimentally observed anomalies despite the fact that the thick Co films are quite rough. ͓S0163-1829͑98͒03810-7͔

We report on an unexpected suppression of the magnetocrystalline anisotropy contribution in epitaxial fcc Co͑110͒ films on Cu͑110͒ below a thickness of d c ϭ(50Ϯ10) Å. For film thicknesses larger than d c the measured anisotropy value agrees with published data. Measurements on films with reduced strain indicate a large strain dependence of d c . A model calculation based on a crystal-field formalism and discussed within the context of band theory, which explicitly takes tetragonal misfit strains into account, reproduces the experimentally observed anomalies. Our results indicate that the usually applied phenomenological description of anisotropies, assuming additive free energy terms for each anisotropy contribution, fails in this case.Progress in understanding the physical origins of magnetic anisotropies in thin magnetic films is largely determined by the accuracy and unambiguity of experimental data and by the success of a more sophisticated theoretical modeling. For uniaxial anisotropy contributions a close agreement between measurements and calculations has been achieved using both band structure calculations 1 and phenomenological models.2 For higher order anisotropies success has been poor. 3,4 This is in part due to the requirements in higher energy resolution, wherein standard theoretical approaches, such as total energy difference calculations based on band structure data, fail.3,4 On the experimental side these contributions are also harder to determine, in particular since they are often one or two orders of magnitude smaller compared to uniaxial contributions also present in thin films. Here we would like to point out that in particular for films of cubic crystallographic symmetry, the fourth-order cubic anisotropy is of key importance in understanding thin film magnetic anisotropy properties, since in the respective bulk materials this anisotropy contribution is of lowest order.In this paper we show that the transformation of the fourth-order, magnetocrystalline bulk anisotropy into uniaxial contributions in the thin film regime as a consequence of tetragonal misfit strains is a characteristic feature of thin film anisotropy. This is demonstrated experimentally for the system of Co͑110͒ films on single-crystalline Cu͑110͒ substrates. The ͑110͒ orientation allows us to differentiate between cubic and uniaxial anisotropy contributions due to different symmetry axes, even if these contributions differ by more than an order of magnitude. We present model calculations based on a crystal-field formalism with energies and parameters interpreted within the context of a band theory. We obtain a transformation of cubic anisotropy into in-plane and out-of-plane uniaxial contributions as a function of the uniaxial distortion of the unit cell due to misfit strain. Our theoretical results are in good agreement with our experimental findings.We have investigated the thickness dependence of all contributing anisotropies and the correlation of the set of determined anisotropy constants on strain and strain relaxat...

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Jager, K. W., Roberts, D. V., and Wilson, Andrew (1970).Brit. J. industr. Med.,27, 273-278. Neuromuscular function in pesticide workers. Electromyography (EMG) provides a sensitive, objective, and speedy method of detecting impairment of nerve and muscle function in pesticide workers who are apparently in good health. Exposure to two organophosphorus compounds (both were dimethyl phosphate esters) was associated with a high incidence (about 50%) of EMG signs of impaired nerve and muscle function. In workers exposed only to organochlorine compounds there was a much lower incidence (about 4%) of abnormal EMG. Exposure to these organophosphorus compounds was not associated with depression of blood cholinesterase activity even in those workers with typical EMG signs. It is concluded that measurement of blood cholinesterase activity does not provide a sensitive index of functional impairment of nerve and muscle.