Ultrasharp magnetization steps in the antiferromagnetic itinerant-electron system LaFe12B6

摘要

The remarkable intrinsic magnetic properties of the LaFe12B6 compound have been studied by neutron powder diffraction (NPD) and magnetization measurements. The NPD measurement reveals that LaFe12B6 exhibits an antiferromagnetic (AFM) structure that can be described with a magnetic propagation vector of (1/4, 1/4, 1/4) below T-N. In the amplitude-modulated model used for the refinement, the Fe magnetic moments are confined to the ab plane with a maximum value of 0.43 mu(B) at 1.5 K. It is shown that the AFM state can be transformed to a ferromagnetic (FM) state via a field-induced first-order transition accompanied with a huge magnetic hysteresis. The LaFe12B6 compound is not only the unique stable RFe12B6 phase, along the rare-earth R series but also presents unique magnetic behavior for a purely 3d itinerant electron system, including particularly low ordering temperature T-N = 36 K, remarkably small Fe moment, unusual amplitude-modulated magnetic arrangement, and a multicritical point in the magnetic phase diagram. In addition, we reveal that at 2 K, the AFM-FM transition is abrupt, leading to a large increase of the Fe magnetic moment up to 1.55 mu(B); the magnetization curve presents ultrasharp steps, giving rise to an unusual staircaselike behavior.