Magnetization and ⁵⁵Mn Hyperfine Field in RMn₂ (R = Rare Earth) Intermetallic Compounds

Abstract

The RMn₂ (R = rare earth) compounds show some interesting crystallographic features. The compounds with R = Gd, Tb and Dy have the cubic Laves phase (C15 type) structure (1), those with Nd (2), Er, Tm (3) and Lu crystallize in hexagonal Laves phase (C14 type) structure, while PrMn₂ has β-Mn type structure (4). The compounds SmMn₂ (5) and HoMn₂ (6) occur in either the C14 or C15 type structure. The compounds for R = La, Ce, Eu and Yb are not known to exist. As noted earlier (3,7), the change in lattice parameter over the RMn₂ series is more rapid than that in the corresponding Fe, Co and Ni series. This may be taken to imply that the Mn valence (and hence its magnetic moment) changes across the series. We have carried out magnetization studies on GdMn₂, DyMn₂ and HoMn₂ and ⁵⁵Mn hyperfine field measurements on several RMn₂ compounds to obtain information about the Mn ion moment. We find that the Mn moment is non-zero in cubic Laves phase RMn₂ compounds, decreases in going from GdMn₂ to DyMn₂ and becomes zero or nearly so in cubic HoMn₂ as well as in hexagonal Laves phase compounds.