Polarized neutron diffraction and Mössbauer spectral study of short-range magnetic correlations in the ferrimagnetic layered compounds(PPh4)[<

Abstract

3 ͔ between 10 and 30 K of broad sextets and doublets in the Mössbauer spectra and the paramagnetic scattering observed in the polarized neutron measurements indicate the coexistence of spin-correlated and spin-uncorrelated regions in the layers of this compound. The polarized neutron scattering profiles and the Mössbauer spectra yield the magnetic exchange correlation length and lifetime, respectively, and the combined results are best understood in terms of layers composed of random frozen, but exchange correlated domains of ca. 50 Å diameter at the lowest temperatures, of spin-correlated domains and spin-uncorrelated regions at intermediate temperatures, and of largely spin-uncorrelated regions above the Néel temperature as determined from magnetometry. The similarity of the Mössbauer spectra of (PPh 4 ) ͓Fe II Fe III (ox) 3 ͔ and (NBu 4 ) ͓Fe II Fe III (ox) 3 ͔ leads to the conclusion that similar magnetic exchange correlations are present in the latter compound.

Progress of Multi Functional Properties of Organic-Inorganic Hybrid System, A[FeIIFeIIIX3] (A = (n-CnH2n+1)4N, Spiropyran; X = C2O2S2, C2OS3, C2O3S)

“…The isomer shift ( IS ) and the quadrupole splitting ( QS ) of the spectrum A at 200 K for ( n -C n H 2n+1 ) 4 N[Fe II Fe III (dto) 3 ](n = 3-6) are quite similar to those ( IS = 0.33 mm/s, QS = 0.35 mm/s at 196 K) of the 57 Fe Mössbauer spectrum for the Fe III ( S = 1/2) site in KBa[Fe III (dto) 3 ]·3H 2 O [56], where the Fe III site is coordinated by six S atoms. On the other hand, the IS and QS of the spectrum B at 200 K are quite similar to those ( IS = 1.235 mm/s, QS = 1.42 mm/s at 190 K) of the 57 Fe Mössbauer spectrum for the Fe II ( S = 2) site in ( n -C 4 H 9 ) 4 N[Fe II Fe III (ox) 3 ](ox = oxalato) [57], where the Fe II site is coordinated by six O atoms. Therefore, it is concluded that the Fe II ( S = 2) and Fe III ( S = 1/2) sites in ( n -C n H 2n+1 ) 4 N[Fe II Fe III (dto) 3 ](n = 3-6) are coordinated by six O atoms and six S atoms, respectively.…”

“…The IS and QS of the spectrum C for n = 3 and 4 are similar to those ( IS = 0.325 mm/s, QS = 0.39 mm/s) of the Fe II ( S = 0) site in [Fe II (bipy) 3 ](ClO 4 ) 2 (bipy = 2,2’-bipyridine) [58]. On the other hand, the IS and QS of the spectrum D for n = 3 and 4 are similar to those ( IS = 0.486, QS = 0.64 at 90 K) of the 57 Fe Mössbauer spectrum for the Fe III ( S = 5/2) site in ( n -C 4 H 9 ) 4 N [Fe II Fe III (ox) 3 ] [57]. …”

“…In connection with this, many bimetallic 2D oxalato complexes exhibiting trigonal R 3c space group have been reported [27,28,29]. In the cases of polycrystalline A[M II Fe III (ox) 3 ] (A = ( n -C 3 H 7 ) 4 N, ( n -C 4 H 9 ) 4 N; M = Mn, Fe), on the other hand, the PXRD profiles show biphasic corresponding to the coexistence of P 6 3 and R 3c phases [57,62,63]. In general, layered materials quite often show the structural disorder arising from the translation of rigid planes.…”

Reentrant Spin Glass and Large Coercive Field Observed in a Spin Integer Dimerized Honeycomb Lattice

“…At 45 K, the spectrum consists of a quadrupole doublet broadened by paramagnetic relaxation and characterized by an isomer shift of δ = 1.198 mm s −1 , and a quadrupole splitting of ΔE Q = 2.695 mm s −1 , which is consistent with high-spin Fe(II) centers. [52] Regarding the entire temperature range of the measurement, the doublets are well developed above 30 K, while the presence of closely connected asymmetric sextets occurs upon cooling below 25 K, which may indicate a long-or shortrange magnetic ordering or a slow relaxation on the Mössbauer timescale. [52]…”

“…[52] Regarding the entire temperature range of the measurement, the doublets are well developed above 30 K, while the presence of closely connected asymmetric sextets occurs upon cooling below 25 K, which may indicate a long-or shortrange magnetic ordering or a slow relaxation on the Mössbauer timescale. [52]…”