Abstract
We use neutron scattering to investigate spin excitations in Sr(Co1-xNix)2As2, which has a c-axis incommensurate helical structure of the two-dimensional (2D) in-plane ferromagnetic (FM) ordered layers for 0.013=x=0.25. By comparing the wave vector and energy dependent spin excitations in helical ordered Sr(Co0.9Ni0.1)2As2 and paramagnetic SrCo2As2, we find that Ni doping, while increasing lattice disorder in Sr(Co1-xNix)2As2, enhances quasi-2D FM spin fluctuations. However, our band structure calculations within the combined density functional theory and dynamic mean field theory (DFT+DMFT) failed to generate a correct incommensurate wave vector for the observed helical order from nested Fermi surfaces. Since transport measurements reveal increased in-plane and c-axis electrical resistivity with increasing Ni doping and associated lattice disorder, we conclude that the helical magnetic order in Sr(Co1-xNix)2As2 may arise from a quantum order-by-disorder mechanism through the itinerant electron mediated Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions.
| Original language | English |
|---|---|
| Article number | 214431 |
| Journal | Physical Review B |
| Volume | 102 |
| Issue number | 21 |
| DOIs | |
| State | Published - Dec 24 2020 |
Funding
Single crystal growth and the work for neutron scattering were supported by U.S. NSF Grant No. DMR-1700081 and Robert A. Welch Foundation Grant No. C-1839 (P.D.). Z.P.Y. was supported by the NSFC (Grant No. 11674030), the Fundamental Research Funds for the Central Universities (Grant No. 310421113), and the National Key Research and Development Program of China, Grant No. 2016YFA0302300. The calculations used high performance computing clusters at BNU in Zhuhai and the National Supercomputer Center in Guangzhou. Neutron diffraction experiments at NIST were supported by the US Department of Energy under EPSCoR Grant No. DE-SC0012432 with additional support from the Louisiana Board of Regents. A portion of this research used resources at the Spallation Neutron Source and High Flux Isotope Reactor, DOE Office of Science User Facilities operated by Oak Ridge National Laboratory.