Hydrogen absorption and magnetic properties of rare earth intermetallics

The magnetic properties of the compounds RMn2and R6Mn23(R = Y, Lu or Th) were studied before and after hydrogen absorption. Hydrogen induced transitions from Pauli paramagnetism to ferromagnetism were observed in YMn2, LuMn2and Th6Mn23. The reverse effect, i.e. changes from ferromagnetism to Pauli paramagnetism were found in Y6Mn23, From X-ray diffraction measurements it was derived that the absorption of hydrogen gas is accompanied by a marked expansion of the crystal lattice but does not lead to a change in crystal structure. The data on the R-Mn compounds are compared with data on R-Fe and R-Co compounds. The possibility is discussed that the main effect responsible for the changes in magnetic properties is the increase in interatomic distances in R-Mn rather than electron-transfer from and to the 3d band as in R-Fe and R-Co, respectively.