Magnetic properties and hydrogen absorption in rare-earth intermetallics of the type RMn2 and R6Mn23

Magnetic properties of the compounds RMn2 and RMn23 (R=Y, Lu, Gd, and Th) were studied before and after hydrogen absorption. Hydrogen-induced transitions from Pauli paramagnetism to ferromagnetism were observed in YMn2, LuMn2, and Th6Mn23. The reverse effect, i.e., changes from ferromagnetism to Pauli paramagnetism, was observed in Y6Mn23. Gradual changes in magnetic properties were found in ThMn2, GdMn2, Lu6Mn23, and Gd6Mn23. It was established by means of x-ray diffraction that the lattice parameters increase considerably upon hydrogen absorption and the crystal structure remains preserved. Attempts have been made to correlate the changes in magnetic properties with the existence of a critical Mn-Mn nearest-neighbor separation