Magnetic and structural properties of the iron oxychalcogenides La2O2Fe2OM2(M

Abstract

We present the results of structural and magnetic phase comparisons of the iron oxychalcogenides La 2 O 2 Fe 2 OM 2 (M = S, Se). Elastic neutron scattering reveals that M = S and Se have similar nuclear structures at room and low temperatures. We find that both materials obtain antiferromagnetic ordering at a Neel temperature T N 90.1 ± 0.16 K and 107.2 ± 0.06 K for M = Se and S, respectively. The magnetic arrangements of M = S, Se are obtained through Rietveld refinement.We find the order parameter exponent β to be 0.129 ± 0.006 for M = Se and 0.133 ± 0.007 for M = S. Each of these values is near the Ising symmetry value of 1/8. This suggests that although lattice and electronic structural modifications result from chalcogen exchange, the nature of the magnetic interactions is similar in these materials.

Local structure of Mott insulating iron oxychalcogenides La2O2Fe2OM2(M=Karki1, Alfailakawi2, Frandsen3 et al. 2021Phys. Rev. BSelf Cite

“…Figure 1 [16], structural studies using x-ray [19] and neutron [16] powder diffraction studies did not observe a structural phase transition in La 2 O 2 Fe 2 O(S, Se) 2 . Inelastic neutron-scattering experiments have indicated the AFM order to be consistent with a 2-k magnetic structure in which two spin stripe phases are oriented 90 • with respect to each other [16,17,21,22].…”

“…The appropriate mixture of these powders was grounded thoroughly, pelletized, and then heated in an evacuated quartz tube at 1030 • C for 72 h. This process was repeated three times. After being pulverized into fine powders, laboratory-based x-ray powder diffraction showed the materials to be of high quality and single phase [12,15,16].…”

“…The Mott insulating iron oxychalcogenides La 2 O 2 Fe 2 OM 2 were first reported as antiferromagnetic (AFM) by Mayer et al [15]. This layered mixed anion material consists of a body-centered tetragonal crystal structure (I4/mmm) with fluoritelike [La 2 O 2 ] 2+ layers and [Fe 2 O] 2+ sheets separated by M 2− anions [16]. In this structure, [Fe 2 O] 2+ consists of an anti-CuO 2 arrangement with an Fe 2+ cation coordinated by four M 2− (above and below the plane) and two in-plane oxygen atoms, forming a tilted Fe-centered FeO 2 Se 4 octahedron [12,15,[17][18][19][20].…”

“…In this structure, [Fe 2 O] 2+ consists of an anti-CuO 2 arrangement with an Fe 2+ cation coordinated by four M 2− (above and below the plane) and two in-plane oxygen atoms, forming a tilted Fe-centered FeO 2 Se 4 octahedron [12,15,[17][18][19][20]. Figure 1 [16], structural studies using x-ray [19] and neutron [16] powder diffraction studies did not observe a structural phase transition in La 2 O 2 Fe 2 O(S, Se) 2 . Inelastic neutron-scattering experiments have indicated the AFM order to be consistent with a 2-k magnetic structure in which two spin stripe phases are oriented 90 • with respect to each other [16,17,21,22].…”

Local Structure of Mott Insulating Iron Oxychalcogenides La$_{2}$O$_{2}$Fe$_{2}$O$M$$_{2}$ ($M$ = S, Se)

“…[14]. This layered mixed anion material consists of a body-centered tetragonal crystal structure (I4/mmm) with fluorite-like [La 2 O 2 ] 2+ layers and [Fe 2 O] 2+ sheets separated by M 2− anions [15]. In this structure, [Fe 2 O] 2+ consists of an anti-CuO 2 arrangement with an Fe 2+ cation coordinated by four M 2− (above and below the plane) and two in-plane oxygen atoms, forming a tilted Fe-centered FeO 2 Se 4 octahedron [13,14,[16][17][18].…”