Ultrasharp magnetization steps in the antiferromagnetic itinerant-electron systemLaFe12B6

Abstract

The remarkable intrinsic magnetic properties of the $\mathrm{LaF}{\mathrm{e}}_{12}{\mathrm{B}}_{6}$ compound have been studied by neutron powder diffraction (NPD) and magnetization measurements. The NPD measurement reveals that $\mathrm{LaF}{\mathrm{e}}_{12}{\mathrm{B}}_{6}$ exhibits an antiferromagnetic (AFM) structure that can be described with a magnetic propagation vector of (\textonequarter{}, \textonequarter{}, \textonequarter{}) below ${T}_{\mathrm{N}}$. In the amplitude-modulated model used for the refinement, the Fe magnetic moments are confined to the $ab$ plane with a maximum value of $0.43 {\ensuremath{\mu}}_{\mathrm{B}}$ 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 $\mathrm{LaF}{\mathrm{e}}_{12}{\mathrm{B}}_{6}$ compound is not only the unique stable $R\mathrm{F}{\mathrm{e}}_{12}{\mathrm{B}}_{6}$ 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 ${T}_{\mathrm{N}}=36\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, 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 $1.55\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}$; the magnetization curve presents ultrasharp steps, giving rise to an unusual staircaselike behavior.