We report neutron scattering measurements of single-crystalline YFe2Ge2 in the normal state, which has the same crystal structure to the 122 family of iron pnictide superconductors. YFe2Ge2 does not exhibit long range magnetic order, but exhibits strong spin fluctuations. Like the iron pnictides, YFe2Ge2 displays anisotropic stripe-type antiferromagnetic spin fluctuations at (π, 0, π). More interesting, however, is the observation of strong spin fluctuations at the in-plane ferromagnetic wavevector (0, 0, π). These ferromagnetic spin fluctuations are isotropic in the (H, K) 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 YFe2Ge2 and also imply that the ferromagnetic correlations may be a key ingredient for iron-based materials.
@article{arxiv.1808.07262,
title = {Coexistence of ferromagnetic and stripe-type antiferromagnetic spin fluctuations in YFe$_2$Ge$_2$},
author = {Hongliang Wo and Qisi Wang and Yao Shen and Xiaowen Zhang and Yiqing Hao and Yu Feng and Shoudong Shen and Zheng He and Bingying Pan and Wenbin Wang and K. Nakajima and S. Ohira-Kawamura and P. Steffens and M. Boehm and K. Schmalzl and T. R. Forrest and M. Matsuda and Yang Zhao and J. W. Lynn and Zhiping Yin and Jun Zhao},
journal= {arXiv preprint arXiv:1808.07262},
year = {2019}
}