Paramagnetic Resonance of Fe³⁺in Sapphire at Low Temperatures

Hybrid electron spin resonance and whispering gallery mode resonance spectroscopy of Fe3+in sapphire

“…Several experiments have attempted to measure the spin-spin relaxation time, or the number of ions involved in the maser process, but have given results which contradict the values given by the manufacturer of the crystals, or those found in the literature. [10][11][12][13] This difference is essentially due to the method used to interact with the ions in sapphire, namely, the excitation of high-Q whispering gallery modes at frequencies coincident with the electron spin resonance (ESR) frequency of the ion. The spatial distribution of these modes acts as a filter, selecting only the population of ions which fall inside its field pattern.…”

Theoretical evaluation of the electron paramagnetic resonance spin Hamiltonian parameters for the impurity displacements for Fe3+ and Ru3+ in corundum

“…For example, the EPR experiments for Ru 3+ (4d 5 ) were carried out, and the anisotropic g factors g and g ⊥ were also measured [16]. They have significant discrepancies from those of Fe 3+ , which are very close to the spin-only value g s (=2.0023) for the case of high spin (S = 5/2) under weak crystal fields [12]. Unlike Fe 3+ , Ru 3+ has strong crystal fields with low-spin S = 1/2 [16,17].…”

“…In addition, it is also regarded as a model material to study crystal fields and local structures (e.g., impurity displacements) for transition-metal dopants by means of optical (crystal-field theory) and electron paramagnetic resonance (EPR) techniques [6][7][8][9][10][11]. Among them, investigations on the spin Hamiltonian parameters zero-field splitting D and the axial displacements of the 3d 5 ions (e.g., Fe 3+ ) in corundum have attracted interest of the workers for the ground orbital singlet 6 A 1g state due to quenching of the orbital angular momentum (L = 0) [12][13][14][15]. The zero-field splittings of the Fe 3+ impurity in corundum (and also Mn 2+ in some fluorides) were elaborately investigated by complete diagonalization procedure [12,13].…”

“…Among them, investigations on the spin Hamiltonian parameters zero-field splitting D and the axial displacements of the 3d 5 ions (e.g., Fe 3+ ) in corundum have attracted interest of the workers for the ground orbital singlet 6 A 1g state due to quenching of the orbital angular momentum (L = 0) [12][13][14][15]. The zero-field splittings of the Fe 3+ impurity in corundum (and also Mn 2+ in some fluorides) were elaborately investigated by complete diagonalization procedure [12,13]. In addition, the axial displacement ΔZ (≈0.04Å) away from the center of the oxygen octahedron along the C 3 axis was obtained from the simple fourth-order perturbation formula based on the weak crystal-field scheme [14].…”

Site Assignment of Fe3+ in Low Symmetry Crystals. Application to NaAlSi3O8

“…The definition of a is the usual one, and in the case of Fe3+ in MgO, a= 205 X 1Q-4 cm-l.l If the crystalline field is no longer cubic, as in AbOa, the EPR spectrum is very different, and its fine structure cannot be described by only one constant; but in this case a= 240X 1Q-4 cm-l . 2 As can be seen, the values of a are not very As we shall have to apply these considerations to the case of nonsymmetrical crystals, only pseudosymmetry will be expected, and it will be necessary to define controls for it.…”