Inelastic neutron scattering study of magneto-structural correlations in NdAlpGa2-psystems

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Abstract
Inelastic neutron scattering has been employed to study the crystalline electric field (CEF) interaction in the compounds NdAlpGa2-p (p=0, 0.5, 1, 1.25, 1.75) which crystallise in different structural phases depending on the aluminium concentration p. The CEF parameters have been determined from the observed energy spectra. In the hexagonal phases the CEF parameters appear to be strongly correlated by geometrical coordination. The CEF parameters correctly predict the easy axis of magnetisation and reasonably explain the observed values of the zero-field magnetisation. The exchange parameters of NdAlGa have been derived from the magnetic structural data up to the fourth-nearest neighbour neodymium shell; their radial dependence turns out to be in excellent agreement with the predictions of the Ruderman-Kittel-Kasuya-Yosida model. The CEF and exchange parameters have been used to calculate the magnetic phase diagram of NdAlGa under uniaxial pressure which is found to exhibit a Lifshitz point.