Abstract
We report magnetization (χ, M), magnetic specific heat (CM), and neutron powder diffraction results on a quasi-two-dimensional (2D) S=2 square lattice antiferromagnet Ba2FeSi2O7 consisting of FeO4 tetrahedrons with highly compressive tetragonal distortion (27%). Despite of the quasi-2D lattice structure, both χ and CM present three-dimensional magnetic long-range ordering below the Néel temperature TN=5.2K. Neutron diffraction data show a collinear Qm=(1,0,1/2) antiferromagnetic (AFM) structure below TN but the ordered moment aligned in the ab plane is suppressed by 26% from the ionic spin S=2 value (4μB). Both the AFM structure and the suppressed moments are well explained by using Monte Carlo simulations with a large single-ion in-plane anisotropy D=1.4 meV and a rather small Heisenberg exchange Jintra=0.15 meV in the plane. The characteristic 2D spin fluctuations are recognized in the magnetic entropy release and diffuse scattering above TN. This new quasi-2D magnetic system also displays unusual nonmonotonic dependence of TN as a function of magnetic field H.
Original language | English |
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Article number | 214434 |
Journal | Physical Review B |
Volume | 104 |
Issue number | 21 |
DOIs | |
State | Published - Dec 1 2021 |
Funding
We thank V. S. Zapf, C. D. Batista, H. Zhang, J.-H. Choi, and D. Bahng for useful discussions and C. Won for crystal growth. This work was supported by the Max Planck POSTECH/Korea Research Initiative, Study for Nano Scale Optomaterials and Complex Phase Materials (Grant No. 2016K1A4A4A01922028) and Grant No. 2020M3H4A2084418, through the National Research Foundation (NRF) funded by MSIP of Korea. Neutron diffraction and data analysis performed by S.-H. D. and A.D.C. were supported by the U.S. DOE, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. M.L. acknowledges the National High Magnetic Field Laboratory in-house science program funded by the National Science Foundation through cooperative Grant No. DMR 1157490, the State of Florida, and the U.S. Department of Energy. We acknowledge the support of the National Institute of Standards and Technology, U.S. Department of Commerce, in providing the neutron research facilities used in this work. The work at Rutgers University was supported by the U.S. DOE under Grant No. DOE: DE-FG02-07ER46382.