Magnetic behavior in the Er(Mn, Al)2 system: Neutron diffraction study

A neutron diffraction study of the Er(Mn 1 - x Al x ) 2 system shows that with the substitution of Mn by Al the hexagonal structure of ErMn 2 becomes unstable and is replaced with a cubic structure. In both phases the Mn ions are nonmagnetic or have very small magnetic moments. At x>0.02 a long-range ferromagnetic order observed in ErMn 2 transforms into a canted antiferromagnetic order with induced Mn spins, which, in turn, at x≥0.15 transforms into a short-range order. In the cubic phase the stability of the antiferromagnetic order is provided by the negative next-nearest-neighbor exchange interaction in the rare-earth lattice, in contrast with other R(Mn,Al) 2 systems, where the antiferromagnetic order is stabilized by the strong negative R-Mn interaction. The evaluated ratio of the exchange parameters describing the next-nearest-neighbor and nearest-neighbor Er-Er interactions is found to be - 1/6.