English

Frustration driven magnetic correlations in the spin-$5/2$ triangular lattice antiferromagnet RbFe(HPO$_{3}$)$_{2}$

Materials Science 2025-11-24 v1

Abstract

A detailed study of the structural and magnetic properties of a spin-5/25/2 triangular lattice antiferromagnet RbFe(HPO3_{3})2_{2} is presented using x-ray diffraction, magnetization, heat capacity, and 31^{31}P nuclear magnetic resonance (NMR) experiments on a polycrystalline sample. The crystal structure features an equilateral triangular lattice of Fe3+^{3+} ions. The thermodynamic measurements reveal the onset of a magnetic long-range order at TN17.8T_{\rm N1} \simeq 7.8 K in zero-field, followed by another low temperature field induced ordering at TN2T_{\rm N2} in higher fields. The transition at TN1T_{\rm N1} is further confirmed from the NMR spin lattice relaxation measurements. The value of the frustration ratio (f7f \simeq 7) implies moderate spin frustration in the compound. The 31^{31}P NMR spectra exhibit two distinct spectral lines corresponding to two inequivalent phosphorus sites (P1 and P2), consistent with the crystal structure. The P1 site is strongly coupled with an isotropic hyperfine coupling of Ahfiso=0.55(2)A_{\rm hf}^{\rm iso} = 0.55(2) T/μB\mu_{\rm B} while the P2 site is weakly coupled with Ahfiso=0.25(3)A_{\rm hf}^{\rm iso} = 0.25(3) T/μB\mu_{\rm B} with the Fe3+^{3+} ions. The magnetic susceptibility and NMR shift data are described well assuming a spin-5/25/2 isotropic triangular lattice antiferromagnetic model with an average exchange coupling of J/kB=2.8(2)J/k_{\rm B} = 2.8(2) K. Below TN1T_{\rm N1}, the spectra evolve into a nearly rectangular powder pattern, indicating a commensurate antiferromagnetic type order. The 31^{31}P spin-lattice relaxation rate well below TN1T_{\rm N1} follows a T3T^3 temperature dependence, implying a two-magnon Raman scattering mechanism in the ordered state. Three well-defined phase regimes are clearly ascertained in the HTH-T phase diagram, reflecting a weak magnetic anisotropy in the compound.

Keywords

Cite

@article{arxiv.2511.17480,
  title  = {Frustration driven magnetic correlations in the spin-$5/2$ triangular lattice antiferromagnet RbFe(HPO$_{3}$)$_{2}$},
  author = {V. Nagpal and Sebin J. Sebastian and Surya P. Patra and S. Shibash and Q. -P. Ding and Y. Furukawa and R. Nath},
  journal= {arXiv preprint arXiv:2511.17480},
  year   = {2025}
}

Comments

14 pages, 13 figures