Paramagnetic Resonance Spectrum of Fe3+ in Guanidinium Aluminum Sulfate Hexahydrate

Abstract

The electron paramagnetic resonance spectrum of Fe³⁺ substituted for Al³⁺ in guanidinium aluminum sulfate hexahydrate, C(NH₂)₃Al(SO₄)₂·6H₂O, was measured at X‐band and K‐band frequencies at room temperature and 77°K. The spectra were observed with the magnetic field parallel to the c axis, which is also the axis of distortion of the octahedra formed by the water molecules. Relative values only of the spin Hamiltonian parameters for an S=5/2 ion were determined; the fitting procedure gave D negative and a and F positive. For room temperature and type‐II sites, the parameters in the spin Hamiltonian were calculated as; g=2.003, D=—0.17601 cm^—1, a=0.020595 cm^—1, and F=0.10047 cm^—1. For type‐I sites at room temperature; g=2.003, D=—0.18508 cm^—1, a=0.021966 cm^—1, and F=0.10530 cm^—1. At 77°K for type‐II sites; g=2.003, D=—0.18902 cm^—1, a=0.053963 cm^—1, and F=0.15203 cm^—1. Type‐I sites at 77°K gave g=2.003, D=—0.19506 cm^—1, a=0.059302 cm^—1, and F=0.16389 cm^—1.