The influence of NH4+ ionic motion on the magnetic structure of (NH4)2FeCl5.H2O: a Mossbauer study

Mossbauer spectroscopy measurements were carried out on the isomorphous salts A2FeCl5.H2O (A identical to K or NH4), between 4.2 K and room temperature. The K salt shows a constant quadrupole splitting Delta , while Delta is strongly temperature dependent for the NH4 salt. This effect is explained in terms of thermally activated reorientations of the NH4+ ion. X-ray diffraction data give no evidence for a structural transformation between 90 K and room temperature. Spectra obtained below TN also show anomalies for the NH4 case, i.e. an enhanced linewidth (indicating magnetic non-equivalence of Fe sites) and magnetisation angles which are inconsistent with a simple canted spin structure. These results suggest a complex magnetic structure for (NH4)2FeCl5.H2O.

[1]  M. Thomas,et al.  Mossbauer investigation of the crystallographic phase transition in Cs2FeCl5.H2O , 1987 .

[2]  N. Nakamura.  NQR Studies of Phase Transitions and Intermolecular Interactions in Crystals , 1986 .

[3]  H. Rechenberg,et al.  Quadrupole interaction and molecular dynamics in A2FeCℓ5.H2O (A=K, Rb, NH4): Evidence for a structural phase transition in (NH4)2FeCℓ5.H2O , 1985 .

[4]  F. Palacio,et al.  The A2[FeX5(H2O)] series of antiferromagnets , 1985 .

[5]  Koji Yamada,et al.  The bond indium-halogen in isomorphous complexes A2InX5.H2O (A=K,NH4,Rb,Cs; X=Cl,Br). A 35Cl 79,81Br, and 115In NQR study , 1983 .

[6]  F. Palacio,et al.  Phase diagram of antiferromagneticK2[FeCl5(H2O)] , 1980 .

[7]  J. Pelzl,et al.  35/37Cl NQR and Raman investigations of molecular motions in (NH4)2SnCl6 , 1980 .

[8]  H. Chihara,et al.  On the anomalous temperature dependence of nor frequencies in some ammonium salts , 1980 .

[9]  H. Chihara,et al.  Effect of ammonium ion reorientation on the anomalous temperature dependence of nuclear quadrupole resonance frequencies , 1979 .

[10]  R. J. Brown,et al.  Erratum: Thermal expansion and 127I nuclear quadrupole coupling in ammonium metaperiodate , 1978 .

[11]  J. Mcelearney,et al.  NONISOMORPHIC ANTIFERROMAGNETIC BEHAVIOR OF TWO ISOMORPHIC SALTS- LOW-TEMPERATURE HEAT CAPACITIES AND MAGNETIC SUSCEPTIBILITIES OF DIAMMONIUM IRON PENTACHLORIDE MONOHYDRATE AND DIPOTASSIUM IRON PENTACHLORIDE MONOHYDRATE , 1978 .

[12]  S. Misra,et al.  Electron paramagnetic resonance of Fe3+ in diammonium indium pentachloride monohydrate , 1977 .

[13]  R. Brown,et al.  Nuclear quadrupole resonance and thermal expansion in perrhenate salts , 1976 .

[14]  M. T. Rogers,et al.  Anomalous temperature dependence of the NQR frequency in NH4ReO4 , 1974 .

[15]  B. Garrett,et al.  Nuclear Quadrupole Resonance of (NH4)2[InCl5H2O] , 1967 .