Relation between crystal structure and physical properties of Rn+1M5+3nB2n phases

We concentrate here on the transition metal rich corner of the ternary R–M–B systems (R is a rare-earth elements, Y or Th and M is a transition metal element), where a series of Rn+1Co3n+5B2n phases exist. This series of compounds derive from the RCo5 crystal structure by an ordered substitution of boron for cobalt leading to a wide family of superstructures. The effects of boron for cobalt substitution on the magnetic properties such as the ordering temperatures or the magnetisation are discussed. The influence of the local environment on the magnitude of the Co magnetic moment is presented. Depending upon the number of boron layers as near neighbours the Co magnetic moment magnitude can vary from 1.8 down to 0 μB. The effect of substituting Fe or Ni for Co is discussed in the light of neutron powder diffraction and X-ray anomalous diffraction, respectively. Whereas the Fe containing compounds are found to keep the original CeCo4B structure type, the Ni containing ones are exhibiting even more complex crystal structures. The preferential location of Fe on the Co 2c site is presented. The magnetic properties of the YCo4−xNixB compounds are investigated. The influence of Th for Y substitution in YCo4B is also presented.