Polarized neutron diffraction study of the extended honeycomb molecular network d20−P(C6D5)4MnFe(C2O4)3

Abstract

Magnetic field driven transition from an antiferromagnetic ground state to a ferrimagnetic state in Rb0.19Ba0.3Mn1.1[Fe(CN)6]·0.48H2O Prussian blue analogue J. Appl. Phys. 112, 093903 (2012); 10.1063/1.4759361Huge influence of hydrogenation on the magnetic properties and structures of the ternary silicide NdMnSiHigh temperature neutron diffraction studies of 0.9 BiFeO 3 -0.1 PbTiO 3The M II and M III magnetic ions in the extended molecular network P͑C 6 D 5 ͒ 4 MnFe͑C 2 O 4 ͒ 3 form a two-dimensional honeycomb magnetic lattice. The Mn 2ϩ and Fe 3ϩ ions alternate in the extended network which is formed by the oxalate (C 2 O 4 ) ligands. These hexagonal layers are separated and charge compensated by large ͓P͑C 6 D 5 ͒ 4 ͔ ϩ ions, positioned in between the honeycomb layers. P͑C 6 D 5 ͒ 4 MnFe͑C 2 O 4 ͒ 3 orders magnetically at T N ϭ27(1) K. A full neutron spin polarization study of the neutron scattering cross section has been carried out which allows the unambigious separation of the magnetic cross section from the total diffraction process. The magnetic structure can be described with the magnetic Shubnikov group R3c. The magnetic moments are antiferromagnetically aligned along the c axis while the Mn 2ϩ and Fe 3ϩ ions form an antiferromagnetic alignment on the honeycomb lattice.

Calorimetric investigation of phase transitions in the layered antiferromagnetic molecule-based material {N(n-C5H11)4[MnIIFeIII(ox)3]}∞(ox=oxalato)

“…Heat capacity anomaly due to the short range ordering above the magnetic transition temperature in the present case can be well represented by S ¼ 5=2 two-dimensional antiferromagnetic Heisenberg model (H=-2J P S i Á S j ) for a honeycomb lattice with J/k B =À3.3 K. This value is very close to J/k B =À3.9(1) K [11] magnetic heat capacities and the theoretical magnetic heat capacities above T N are in good agreement in the present case. However, as far as the relevant theory is concerned, a two-dimensional pure Heisenberg system cannot exhibit any phase transition due to spin ordering [24].…”

“…Below T N , this and analogous materials exhibited a jump in the magnetization arising probably from the uncompensated magnetic moment [4,6]. Vissar et al [11] assumed the similar uncompensated magnetization observed in {P(C 6 D 5 ) 4 [Mn IIFe III (ox) 3 ]} N as the manifestation of weak ferromagnetic alignment of Mn II and Fe III spins at low temperatures. From the single crystal magnetization measurements of {N-(n-C 5 H 11 ) 4 [Mn IIFe III (ox) 3 ]} N , Carling et al [17] observed an uncompensated magnetization below 27 K. Results from M .…”

“…The single crystal structure analysis of this material at room temperature revealed that the structure consists of hexagonal layers of alternating Mn II and Fe III metal ions bridged by oxalato ligand, separated by the layers containing only N(n-C 5 H 11 ) 4 + cations with the n-C 5 H 11 chains extended through the terminal bonds twisted towards the gauche form [17]. Polarized neutron diffraction study of analogous {P(C 6 D 5 ) 4 [Mn II Fe III (ox) 3 ]} N compound (T N = 27 K, Curie-Weiss constant, y ¼ À128 K, intralayer interaction J/k B =À3.9(1) K) revealed that Mn II and Fe III ions are antiferromagnetically arranged in the honeycomb layers, but with a ferromagnetic stacking of the Mn II and Fe III ions between the layers along the hexagonal c-axis which might lead to a very weak ferromagnetic interlayer interaction [11].…”

“…The magnetic property of this material system may mimic that of a two-dimensional classical antiferromagnet [16]. This system {A[Mn II Fe III (ox) 3 ]} N has received much attention recently [4,6,11,13,17]. Compounds with different organic cations with the same Mn II -ox-Fe III layer have been studied magnetically.…”

“…In quasi-2D materials, the organic cations located between the anionic M II -ox-M III layers determine the dimensionality as well as the extent of interlayer separation of the system. Among them, {A[M IIFe III (ox) 3 ]} N series of materials have been widely studied due to their unusual magnetic properties [4,[9][10][11][12][13][14][15]. The magnetic interaction between two nearest neighbor metal ions in this class of materials has been found to be a function of intralayer cation-cation ''bite-angle'' subtended by the oxalato ligand and the degree of trigonal distortion around the cation sites, which is reflected in the change in the magnetic properties of the compounds with M II =Fe depending on the nature of the nonmagnetic organic cations [4].…”