Magnetic structure of CoO studied by neutron and synchrotron X-ray diffraction

中性子回折と放射光X線回折で調べたCoOの磁気構造

富安 啓輔*; 稲見 俊哉; 池田 直*

Tomiyasu, Keisuke*; Inami, Toshiya; Ikeda, Naoshi*

289K以下でCoOは三回軸に平行な伝播ベクトルで表される長距離磁気秩序を示す。しかしながら格子は四回軸と三回軸の混ざった単斜晶にひずむ。この矛盾を明らかにするためにわれわれは中性子回折実験と放射光X線回折実験を単結晶CoOに対して行い、新しい四回軸に平行な伝播ベクトルで表される一連の磁気反射を転移点以下で見いだした。この結果は正方晶と三方晶の伝播ベクトルを持ったCoOの新しい磁気構造を提案するもので、これは単斜晶の対称性を持ち、格子のひずみとも一致する。

Below = 289 K, the antiferromagnet CoO exhibits magnetic long-range order described by a propagation vector along the trigonal axis, whereas the lattice is distorted monoclinicly along both the tetragonal and the trigonal axes. In order to elucidate this inconsistency, we performed neutron and synchrotron X-ray diffraction experiments on single crystals of CoO, and found a new series of magnetic reflections represented by a propagation vector along the tetragonal axis below N. These results suggest an altered magnetic structure of CoO, which includes both the trigonal and the tetragonal propagation vectors, has a monoclinic symmetry and which is in accordance with the distorted lattice symmetry.