Simultaneous phase separation and ferromagnetic transition in NdIn3−xCox

The crystal structures and magnetic properties of 3d transition metal Co dilute NdIn3−xCox alloys have been studied by means of X-ray diffraction and magnetic measurements. Co doping into NdIn3 causes the phase separation from cubic AuCu3-type to hexagonal CaIn2-type structure associated with a magnetic transition from paramagnetic to ferromagnetic. Rietveld's structural refinement confirms that two nonequivalent crystal positions (2b and 4f) exist in one unit cell for the hexagonal phase, which are occupied by 2Nd and 4(In,Co), respectively. The ferromagnetism of NdIn3−xCox is suggested to be caused by the spin-spin interactions between Co and Co atoms. The increase of magnetic moment in NdIn3−xCox might be due to the partial substitution of non-magnetic element In by 3d transition metal Co in the host material and thus a net moment is produced.