Coexistence of ferromagnetic and stripe-type antiferromagnetic spin fluctuations in YFeGe

YFeGeにおける強磁性、及び、ストライプ型の反強磁性のスピン揺らぎの共存

Wo, H.*; Wang, Q.*; Shen, Y.*; Zhang, X.*; Hao, Y.*; Feng, Y.*; Shen, S.*; He, Z.*; Pan, B.*; Wang, W.*; 中島 健次  ; 河村 聖子   ; Steffens, P.*; Boehm, M.*; Schmalzl, K.*; Forrest, T. R.*; 松田 雅昌*; Zhao, Y.*; Lynn, J. W.*; Yin, Z.*; Zhao, J.*

Wo, H.*; Wang, Q.*; Shen, Y.*; Zhang, X.*; Hao, Y.*; Feng, Y.*; Shen, S.*; He, Z.*; Pan, B.*; Wang, W.*; Nakajima, Kenji; Kawamura, Seiko; Steffens, P.*; Boehm, M.*; Schmalzl, K.*; Forrest, T. R.*; Matsuda, Masaaki*; Zhao, Y.*; Lynn, J. W.*; Yin, Z.*; Zhao, J.*

We report neutron scattering measurements of single-crystalline YFeGe in the normal state, which has the same crystal structure as the 122 family of iron pnictide superconductors. YFeGe does not exhibit long-range magnetic order but exhibits strong spin fluctuations. Like the iron pnictides, YFeGe displays anisotropic stripe-type antiferromagnetic spin fluctuations at (). More interesting, however, is the observation of strong spin fluctuations at the in-plane ferromagnetic wave vector (). These ferromagnetic spin fluctuations are isotropic in the () plane, whose intensity exceeds that of stripe spin fluctuations. Both the ferromagnetic and stripe spin fluctuations remain gapless down to the lowest measured energies. Our results naturally explain the absence of magnetic order in YFeGe and also imply that the ferromagnetic correlations may be a key ingredient for iron-based materials.