Spin dynamics in antiferromagnetic oxypnictides and fluoropnictides: LaMnAsO, LaMnSbO, and BaMnAsF

Journal Article · 15 April 2020 · Physical Review B

DOI: https://doi.org/10.1103/PhysRevB.101.155119 · OSTI ID:1616551

Islam, Farhan ^[1]; Gordon, Elijah ^[1]; Das, Pinaki ^[1]; Liu, Yong ^[1]; Ke, Liqin ^[1]; Abernathy, Douglas L.  ^[2]; McQueeney, Robert J. ^[3]; Vaknin, David  ^[3]

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1. Ames Laboratory (AMES), Ames, IA (United States)
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
3. Ames Laboratory (AMES), Ames, IA (United States); Iowa State Univ., Ames, IA (United States)

In this study, inelastic neutron scattering (INS) from polycrystalline antiferromagnetic LaMnAsO, LaMnSbO, and BaMnAsF are analyzed using a $J_1\text{-}{J}_2\text{-}{J}_c$ Heisenberg model in the framework of the linear spin-wave theory. All three systems show clear evidence that the nearest- and next-nearest-neighbor interactions within the Mn square lattice layer ( $J_1$ and $J_2$) are both antiferromagnetic (AFM). However, for all compounds studied the competing interactions have a ratio of $2J_2/J_1<1$, which favors the square lattice checkerboard AFM structure over the stripe AFM structure. The interplane coupling $J_c$ in all three systems is on the order of $~3\times {10}^{-4}{J}_1$, rendering the magnetic properties of these systems with quasi-two-dimensional character. The substitution of Sb for As significantly lowers the in-plane exchange coupling, which is also reflected in the decrease of the Néel temperature, $T_{\mathrm{N}}$. Although BaMnAsF shares the same MnAs sheets as LaMnAsO, their $J_1$ and $J_2$ values are substantially different. Lastly, using density functional theory, we calculate exchange parameters $J_{ij}$ to rationalize the differences among these systems.

• Research Organization: Ames Laboratory (AMES), Ames, IA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division
• Grant/Contract Number: AC02-07CH11358
• OSTI ID: 1616551
• Alternate ID(s): OSTI ID: 1615072
• Report Number(s): IS-J 10,206; PRBMDO; TRN: US2106470
• Journal Information: Physical Review B, Vol. 101, Issue 15; ISSN 2469-9950
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English