Observation of spin relaxation and magnetic ordering by transferred hyperfine interactions

Mössbauer measurements on ¹²⁹I in iodo (bispyrrolidinedithiocarbamato) Fe^III show the occurence of magnetic ordering at 2.18°K and relaxation effects in the paramagnetic region. The transition is confirmed by measurements on ⁵⁷Fe. The effective magnetic field at the ¹²⁹I nucleus at 1.4°K is 66^± 2kG and is perpendicular to the direction of the iron-iodine bond. The number of p and s holes in the (5s)² (5p)⁶ valence shell of iodine is determined from the values of the quadrupole coupling constant and the isomer shift.     

Mössbauer study of 1% <Superscript>57</Superscript>Fe doped ferromagnetic insulator La<Subscript>0.825</Subscript>Ca<Subscript>0.175</Subscript>MnO<Subscript>3</Subscript>

We have employed magnetization measurements, M?ssbauer and ESR spectroscopic techniques, in order to study the ferromagnetic insulating (FMI) compound La_1-xCa_xMnO₃ (x=0.175) doped with 1% ⁵⁷Fe. We have used two samples; one prepared in air which has cation vacancies and a second in inert atmosphere, which is stoichiometric. An abrupt change of the experimental results is obtained, by all techniques, in the ferromagnetic insulating regime, in the temperature region of T_O/O//≈60 K, where an orbital rearrangement is suggested to occur. An analysis of these findings points to an orbital rearrangement transformation. Ferromagnetic resonance reveals considerable differences between stoichiometric and cation deficient samples, indicating anisotropy of the exchange interactions in the former sample with significant temperature dependence, most pronounced in the vicinity of T_O/O//     

Mössbauer Study of Materials Displaying Colossal Magnetic Resistivity

Hyperfine Interactions - In the last decade the discovery of colossal magnetoresistance in Mn based perovskites brought various perovskite and spinel materials, displaying the effect of...     

Studies of the pyrazine-bridged antiferromagnets Fe(pyz)mX2 (m=1, X=CF3SO3 −, NCO−; m=2, X=NCS−)

Mössbauer and magnetic susceptibility data are reported for the title complexes. The data demonstrate that these pyrazine-bridged complexes represent examples of low-dimensional lattices with anisotropic magnetic exchange arising from different interaction strengths of the bridging ligands.     

Size effects on the magnetic properties of fine Fe-Cr particles

The magnetic and structural properties of Fe_1003−xCr_x ultrafine particles with x = 5–20 have been studied as a function of particle size. Particles with a size in the range of 80–360 Å were prepared by gas evaporation under argon atmosphere. The particles with smaller diameter had a high coercivity at low temperatures and showed a stronger temperature dependence of coercivity. The x = 20 particles with a size 80 Å had a coercivity about 2100 Oe at 10 K with a superparamagnetic blocking temperature about 150 K. Mössbauer spectra showed the presence of Fe-Cr, -Fe and Fe-oxide components in the bigger particles, and Fe-Cr and Fe-oxides in the smaller particles. The coercivity at low temperatures increased with decreasing particle size and this was attributed to the higher percentage of Fe-oxide on the surface of the smaller particles. This interpretation was further supported by the temperature dependence of coercivity of Fe–Cr particles sandwiched between two Ag films.