Experiment and theory of actinide intermetallic magnetism: a test case of NpCo2

A detailed neutron study using a single crystal has measured the individual magnetic moments on the Np and Co sites in the compound NpCo2. Furthermore, by studying the angular dependence of the magnetic amplitude, we are able to assign individual values to the spin and orbital moments. These are both large, and oppositely directed. A first-principle LMTO calculation including relativistic effects and both spin and orbital polarization is in excellent agreement with experiment, as far as the partial cancellation of the spin and orbital moments is concerned. This agreement has general implications for our understanding of the complex magnetic behaviour of actinide intermetallic compounds