Abstract
We report here a comprehensive study of the AFM structures of the Eu and Mn magnetic sublattices as well as the interplay between Eu and Mn magnetism in this compound by using both polarized and non-polarized single-crystal neutron diffraction. Magnetic susceptibility, specific heat capacity measurements and the temperature dependence of magnetic diffractions suggest that the AFM ordering temperature of the Eu and Mn moments is at 22 and 337 K, respectively. The magnetic moments of both Eu and Mn ions are oriented along the crystallographic $c$ axis, and the respective magnetic propagation vector is $\textbf{k}_{Eu} = (0,0,1)$ and $\textbf{k}_{Mn}=(0,0,0)$. With proper neutron absorption correction, the ordered moments are refined at 3 K as 7.7(1) $\mu_B$ and 4.1(1) $\mu_B$ for the Eu and Mn ions, respectively. In addition, a spin-flop (SF) phase transition of the Eu moments in an applied magnetic field along the $c$ axis was confirmed to take place at a critical field of B$_c$ $\sim$ 5.3 T. The evolution of the Eu magnetic moment direction as a function of the applied magnetic field in the SF phase was also determined. Clear kinks in both field and temperature dependence of the magnetic reflections ($\pm1$, 0, 1) of Mn were observed at the onset of the SF phase transition and the AFM order of the Eu moments, respectively. This unambiguously indicates the existence of a strong coupling between Eu and Mn magnetism. The interplay between two magnetic sublattices could bring new possibilities to tune Dirac fermions via changing magnetic structures by applied fields in this class of magnetic topological semimetals.
Highlights
Dirac/Weyl semimetals have attracted a great deal of recent research interest largely owing to their exotic quantum states and emergent phenomena as well as their high potentials for future technological applications [1]
The lattice parameter c = 22.614(5) Å at room temperature extracted from x-ray diffraction (XRD) is quite consistent with the previous results [39]
The fieldand temperature-dependence experiments do show strong evidence for the interplay between Eu and Mn sublattices, and the strength of the interplay could be affected by the applied field
Summary
Dirac/Weyl semimetals have attracted a great deal of recent research interest largely owing to their exotic quantum states and emergent phenomena as well as their high potentials for future technological applications [1]. By spontaneous or externally induced time-reversal symmetry breaking, EuMnBi2 and YbMnBi2 could be driven to host Weyl physics Such magnetic Dirac materials where the magnetic and conducting layers are coupled but separated spatially provide an ideal platform to study the interplay between magnetic moments and Dirac carriers, which may find promising application potential in spintronics devices. It was found that the magnetic order of Eu ions in EuMnBi2 is field tunable and a spin-flop transition occurs at the applied field H = 5.3 T along the c axis [6,35,39] This suggests that such an interplay between different magnetic sublattices in this class of magnetic Dirac materials could be used to tune their intrinsic magnetic structures under moderate magnetic fields, subsequently, to impact their electronic behaviors related to Dirac fermions. We propose an anisotropic X X Z spin Hamiltonian model that includes a dominant isotropic antiferromagnetic exchange interaction with a small planar exchange anisotropy as well as a small uniaxial single-ion anisotropy for the Eu sublattice in EuMnBi2
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
