Abstract
Whereas magnetic frustration is typically associated with local-moment magnets in special geometric arrangements, here we show that is a candidate for frustrated itinerant magnetism. Using inelastic neutron scattering (INS), we find that antiferromagnetic (AF) spin fluctuations develop in the square Co layers of below K centered at the stripe-type AF propagation vector of , and that their development is concomitant with a suppression of the uniform magnetic susceptibility determined via magnetization measurements. We interpret this switch in spectral weight as signaling a temperature-induced crossover from an instability toward ferromagnetism ordering to an instability toward stripe-type AF ordering on cooling, and show results from Monte-Carlo simulations for a Heisenberg model that illustrates how the crossover develops as a function of the frustration ratio . By putting our INS data on an absolute scale, we quantitatively compare them and our magnetization data to exact-diagonalization calculations for the model [N. Shannon et al., Eur. Phys. J. B 38, 599 (2004).], and show that the calculations predict a lower level of magnetic frustration than indicated by experiment. We trace this discrepancy to the large energy scale of the fluctuations ( meV), which, in addition to the steep dispersion, is more characteristic of itinerant magnetism.
5 More- Received 23 October 2018
- Revised 19 June 2019
DOI:https://doi.org/10.1103/PhysRevB.100.054411
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