Magnetic excitations in the orbital disordered phase of MnVO

MnVOの軌道無秩序相における磁気励起

松浦 慧介*; 佐賀山 基*; 上原 周*; 新居 陽一*; 梶本 亮一  ; 蒲沢 和也*; 池内 和彦*; Ji, S.*; 阿部 伸行*; 有馬 孝尚*

Matsuura, Keisuke*; Sagayama, Hajime*; Uehara, Amane*; Nii, Yoichi*; Kajimoto, Ryoichi; Kamazawa, Kazuya*; Ikeuchi, Kazuhiko*; Ji, S.*; Abe, Nobuyuki*; Arima, Takahisa*

We have investigated the temperature dependence of magnetic dynamics in a spinel-type vanadium oxide MnVO by inelastic neutron scattering. The scattering intensity of excitation around 20 meV disappears in the collinear intermediate-temperature cubic-ferrimagnetic phase, which reveals that this excitation should be peculiar to the orbital ordered phase. We have found a weakly dispersive mode emergent from a non-integer wavevector at 56 K, which lies in the cubic-ferrimagnetic phase between non-coplanar ferrimagnetic and paramagnetic phases. This indicates that the probable presence of an incommensurate instability in the simple collinear structure.