Uncover the magneto-structural coupling in the MnCoGe-based magnetocaloric alloys

Our recent results show that including 1 at.% of boron atoms in the MnCoGe alloy can make the otherwise separated ferromagnetic and orthorhombic-hexagonal structural transitions coincide, i.e. the realization of a magneto-structural transition. This leads to a giant magnetocaloric effect. However, the coupling mechanism of the magnetic and structural transitions is still not clear. Magnetic measurements suggest partial quenching of sublattice magnetic moments during the structural transition. We have solved the magnetic structure of the orthorhombic phase using neutron diffraction. Here we propose to perform neutron diffraction on the hexagonal MnCoGe phase. This work will allow us to elucidate the roles of the Mn and Co moments in the magneto-structural transition as well as the interplay between the magnetic and structural transition in the MnCoGe-based magnetocaloric materials.

我们的最新研究结果表明，在锰钴锗（MnCoGe）合金中掺入1原子百分比（at.%）的硼原子，可使原本相互分离的铁磁性转变与正交晶-六方晶结构转变实现重合，即达成磁结构转变（magneto-structural transition）。此举可产生巨磁热效应（magnetocaloric effect）。然而，磁转变与结构转变之间的耦合机制仍未明确。磁性测量结果显示，在结构转变过程中，亚晶格磁矩发生了部分猝灭。我们已通过中子衍射解析了该合金正交晶相的磁结构。在此，我们提议对六方晶相锰钴锗合金开展中子衍射实验。本研究将阐明锰（Mn）与钴（Co）磁矩在磁结构转变中的作用，以及锰钴锗基磁热材料中磁转变与结构转变之间的相互作用机制。