2024/07/25 by Zhu, Weiqin, Wang, Panshuo, Zhu, Haiyan +4 · 1 citation
#FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Strongly Correlated Electrons (cond-mat.str-el)
paper · doi:10.48550/arxiv.2407.17859
Type-II multiferroicity, where electric polarization is induced by specific spin patterns, is crucial in fundamental physics and advanced spintronics. However, the spin model and magnetoelectric coupling mechanisms in prototypical type-II multiferroic CuFeO2 and Al-doped CuFeO2 remain unclear. Here, by considering both spin and alloy degrees of freedom, we develop a magnetic cluster expansion method, which considers all symmetry allowed interactions. Applying such method, we not only obtain realistic spin model that can correctly reproduce observations for both CuFeO2 and CuFe1-xAlxO2, but also revisit well-known theories of the original spin-current (SC) model and p-d hybridization model. Specifically, we find that (i) a previously overlooked biquadratic interaction is critical to reproduce the \uparrow\uparrow\downarrow\downarrow ground state and excited states of CuFeO2; (ii) the combination of absent biquadratic interaction and increased magnetic frustration around Al dopants stabilizes the proper screw state; and (iii) it is the generalized spin-current (GSC) model that can correctly characterize the multiferroicity of CuFeO2. These findings have broader implications for understanding novel magnetoelectric couplings in, e.g., monolayer multiferroic NiI2.