Neutron diffraction on TmNi₄Al

Abstract

Tm and its alloys are known to create non-collinear magnetic phases, therefore this same can be expected in the case of TmNi 4 Al. Indeed, we have observed that this compound, contrary to the other RNi 4 Al members, exhibits an additional hump in the ac magnetic susceptibility at T C2 = 2.8 K apart from the main peak at T C1 = 5.8 K. It may imply a double phase transition or an impurity phase. The magnetization curves and the neutron diffraction have been measured above the higher temperature transition, between the two transitions and below the lower temperature peak of the ac susceptibility. However, magnetization curves as well as the neutron diffraction patterns do not provide any evidence of the antiferromagnetic ordering but suggest a ferromagnetic state. There is only an increase of the intensities observed between 4.2 K and 1.8 K. Therefore, the two peaks in the ac magnetic susceptibility can be ascribed to a switch between two various slightly non-collinear orderings of the magnetic moments and/or a small distortion of the crystallographic structure. The latter possibility results from the observed small broadening of the diffraction peaks.

Neutron diffraction and magnetization measurements on CeNi4.2Mn0.8 and Y0.7Ni4.2Mn0.8

“…The hexagonal structure has been also confirmed in our previous studies on the CeNi 4.2 Mn 0.8 crystal [8]. This structure is of the CaCu 5 -type and is well known for a wide range of the RNi 4 M compounds (R = Y or rare earth; M = Al, Cu, Si, Ga) [9][10][11][12], derived from RNi 5 .…”