Physical properties of a quasi-two-dimensional square lattice antiferromagnet Ba${}_2$FeSi${}_2$O${}_7$

Abstract

We report the magnetization ($\chi$, $M$), specific heat ($C_{\text{P}}$), and neutron powder diffraction results on a quasi-two-dimensional $S$ = 2 square lattice antiferromagnet Ba${}_2$FeSi${}_2$O${}_7$ consisting of FeO${}_4$ tetragons with a large compressive distortion (27%). Despite of the quasi-two-dimensional lattice structure, both $\chi$ and $C_{\text{P}}$ present three dimensional magnetic long-range order below the Néel temperature $T_{\text{N}}$ = 5.2 K. Neutron diffraction data shows a collinear $Q_m$ = (1,0,0.5) antiferromagnetic (AFM) structure with the in-plane ordered magnetic moment suppressed by 26% below $T_{\text{N}}$. Both the AFM structure and the suppressed moments are well explained by the Monte Carlo simulation with a large single-ion ab-plane anisotropy $D$ = 1.4 meV and a rather small in-plane Heisenberg exchange $J_{\text{intra}}$ = 0.15 meV. The characteristic two dimensional spin fluctuations can be recognized in the magnetic entropy release and diffuse scattering above $T_{\text{N}}$. This new quasi-2D magnetic system also displays unusual non-monotonic dependence of the $T_{\text{N}}$ as a function of magnetic field $H$.

arXiv comment23 pages

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Cited by in corpus (5)

• Field-induced spin level crossings within a quasi-XY antiferromagnetic state in Ba${}_2$FeSi${}_2$O${}_7$
• Magnetic properties of a spin-orbit entangled Jeff = 1/2 honeycomb lattice
• Study of Staggered Magnetization in the Spin-$S$ Square-Lattice Heisenberg Model Using Spiral Boundary Conditions
• Magnetic structure of the noncentrosymmetric magnet Sr2MnSi2O7 through irreducible representation and magnetic space group analyses
• Magnetic excitations in the noncentrosymmetric magnet Sr2MnSi2O7