First-order magnetic phase transition in TmGa

Abstract

In a recent paper we determined the magnetic structure of the intermetallic compound TmGa using a combination of neutron diffraction and 169Tm Mössbauer spectroscopy. This compound shows two magnetic ‘events’ in its ac-susceptibility, at 15(1) K and 12(1) K. The upper transition is to an incommensurate antiferromagnetic structure which gives way to a dominant ferromagnetic structure at the lower transition. However, the Mössbauer results suggested that the 12 K transition is in fact first-order. In order to resolve this question, we have carried out a high-resolution, neutron diffraction thermal scan around these magnetic ordering events and we have observed clear thermal hysteresis in the behaviour of the magnetic scattering intensity. The observation of such hysteresis confirms our earlier suggestion of a first-order magnetic ordering in TmGa.