Nuclear and magnetic spin structure of the antiferromagnetic triangular lattice compound LiCrTe2 investigated by $$\mu ^+$$SR, neutron and X-ray diffraction

Abstract

Two-dimensional (2D) triangular lattice antiferromagnets (2D-TLA) often manifest intriguing physical and technological properties, due to the strong interplay between lattice geometry and electronic properties. The recently synthesized 2-dimensional transition metal dichalcogenide LiCrTe$$_2$$ 2 , being a 2D-TLA, enriched the range of materials which can present such properties. In this work, muon spin rotation ($$\mu ^+$$ μ + SR) and neutron powder diffraction (NPD) have been utilized to reveal the true magnetic nature and ground state of LiCrTe$$_2$$ 2 . From high-resolution NPD the magnetic spin order at base-temperature is not, as previously suggested, helical, but rather collinear antiferromagnetic (AFM) with ferromagnetic (FM) spin coupling within the ab-plane and AFM coupling along the c-axis. The value if the ordered magnetic Cr moment is established as $$\mu _{\textrm{Cr}}= 2.36~\mu _{\textrm{B}}$$ μ Cr = 2.36 μ B . From detailed $$\mu ^+$$ μ + SR measurements we observe an AFM ordering temperature $$T_{\textrm{N}}\approx 125$$ T N ≈ 125 K. This value is remarkably higher than the one previously reported by magnetic bulk measurements. From $$\mu ^+$$ μ + SR we are able to extract the magnetic order parameter, whose critical exponent allows us to categorize LiCrTe$$_2$$ 2 in the 3D Heisenberg AFM universality class. Finally, by combining our magnetic studies with high-resolution synchrotron X-ray diffraction (XRD), we find a clear coupling between the nuclear and magnetic spin lattices. This suggests the possibility for a strong magnon–phonon coupling, similar to what has been previously observed in the closely related compound LiCrO$$_2$$ 2 .

Synthesis and anisotropic magnetic properties of LiCrTe 2 single crystals with a triangular-lattice antiferromagnetic structure

“…This negative thermal expansion observed is consistent with the recent results of synchrotron data on polycrystalline LiCrTe 2 conducted by Nocerino et al, and has been observed in other intercalated chromium tellurides [22,41]. Also a similar T N ≈ 125 K from µ + SR measurements was observed for the powder sample from Nocerino et al [41]. Considering the stoichiometric Li-content of the powder sample, the lower critical temperature derived from the µ + SR measurements could reflect the strongly dynamic character of the magnetic interactions, or the enhanced T N ≈ 148 K in the single crystals might be related to local strain effects in either sample.…”

“…The neutron diffraction experiment conducted at T = 175 K (above the AFM transition, see figure 1(c)) and T = 1.8 K, see figure 2(b), show a decrease of the c axis but an increase of the a axis on lowering the temperature, indicating a shortening of the Cr-Te, Li-Te and Te-Te distances but an increase in the Cr-Cr distance, see table 1. This negative thermal expansion observed is consistent with the recent results of synchrotron data on polycrystalline LiCrTe 2 conducted by Nocerino et al, and has been observed in other intercalated chromium tellurides [22,41]. Also a similar T N ≈ 125 K from µ + SR measurements was observed for the powder sample from Nocerino et al [41].…”

“…We find the magnetic structure of single crystalline LiCrTe 2 to be A-type antiferromagnetic, with the Cr moments oriented along the c-axis. This result is in excellent agreement with earlier findings in polycrystalline LiCrTe 2 , where the same magnetic structure was found [41]. The cell parameters and magnetic moment resulting from the refinement are summarized in table 1 together with the Bragg R agreement factors for the nuclear and magnetic LiCrTe 2 phases.…”

Magnetic nature of wolframite MgReO4

“…Another, here more likely, scenario is that a spin reorientation occurs, creating a complex magnetic structure below 65 K. The zero phase of the ZF oscillations tells us that it should be a commensurate spin structure. Consequently, this suggests that a canted AF structure is formed below T Cant ≈ 65 K, while a collinear (CL) The occurrence of canted AF orders is usually a result of competing magnetic interactions, in qualitative agreement with other systems showing a similar behavior [15,16,17,18,19,3]. No detailed structural refinement of the atomic positions in MgReO 4 is reported.…”

Na-ion dynamics in the solid solution NaxCa1−xCr2O4 studied by muon spin rotation and neutron diffraction

“…20 This rare condition is responsible for the unconventional low temperature microscopic properties 21 that make NaCr 2 O 4 a fascinating study case also from a fundamental research perspective. 22 The compound crystallizes in the orthorhombic space group 62 (Pnma), in which Cr cations occupy two distinct crystallographic positions (labelled as Cr I and Cr II in Fig. 1) surrounded by octahedrally coordinated oxygen atoms.…”