Magnetic Susceptibility Calculated from Correlation-Lengths Derived by Mössbauer Relaxation Spectra

Abstract

From the knowledge of the spin correlation functions derived from Mössbauer relaxation spectra of quasi-one-dimensional A 2 MnoyxFe ()() 2F< i (H20) we could fit the antiferromagnetic susceptibilities of A 2 MnF 5 (H 2 0) with A = Na , (NH 4 ) + , K + , Rb + obtained for single crystal samples. The calculation yielded characteristic parameters such as the local anisotropy D, the intra-chain exchange energy J, the inter-chain exchange energy \ J'\, the Neel temperature T N , and the spin canting angle (p.

Fluorine-bridged chain compounds as models in magnetochemistry: structures and magnetism of (imidH)2[Fe2oxF6] and [Fe2oxF4(DMSO)4]

“…In connection with this, we mention that in our previous work these excitations were found also by inelastic neutron scattering (high resolution neutron spectroscopy) on large single crystals of (NH 4 ) 2 MnF 5 , (ND 4 ) 2 MnF 5 and Na 2 MnF 5 [38,39,40], in good agreement with our Mössbauer-spectroscopic results [24,25,31,32]. …”

“…Additionally, there is, as already discussed for 1D compounds [25,31,32], some slight temperature-independent asymmetry (of the line intensities) over the temperature range T > 40 K that we attribute to sample texture. The two lines have unequal intensities, the lower energy one being more intense.…”

“…We define this temperature as the Néel temperature for (imidH) 2 [Fe 2 oxF 6 ], as done in former experiments [24] where the temperature of divergence of magnetization coincided with T N as derived from single crystal studies by elastic and inelastic neutron scattering experiments and magnetic susceptibility measurements. Previously, from our Mössbauer spectroscopic studies and measurements of the temperature dependence of the magnetization on single crystals of some one-dimensional fluoromanganates(III) as (NH 4 )MnF 5 , (ND 4 ) 2 MnF 5 , and Na 2 MnF 5 with strong axial anisotropy we derived on the basis of the magnetic correlation functions an analytical expression for the temperature dependence of magnetic susceptibility [25] w Powder % w k þ 2w ? ¼…”

“…The two lines have unequal intensities, the lower energy one being more intense. This can be explained [25,31,32] by non-random orientation of crystallites in the absorber, since sample crystals readily cleave into needles orienting preferentially parallel to the absorber planes. From the intensity difference we conclude that the lower-energy line is the ðAE1=2 !…”

“…In the light of this discussion, we will return to our previously reported studies of the 57 Fe Mössbauer spectra of the iron doped Ising-type quasi 1D antiferromagnets (NH 4 ) 2 MnF 5 , (ND 4 ) 2 MnF 5 and Na 2 MnF 5 [24,25,31,32].…”