Effect of Monoclinic Symmetry on the EPR Spectra of Gd³⁺‐Doped Hydrated Single Crystals of Rare‐Earth Trichlorides

Abstract

Room-temperature X-band EPR data for Gds+-doped isostructural rare-earth trichloride hexahydrates are analyzed using a rigorous least-squares-fitting procedure. Discussion of the three forms of spin Hamiltonian corresponding to the orientations of the two-fold monoclinic symmetry axis C, parallel to the magnetic axes X, Y, and 2 is provided. It is found that for, C, I I Y, a significantly lower value of x2, representing the goodness of fit, is obtained. A discussion of the determination of degree of monoclinicity, as revealed by the spin Hamiltonian parameters, is provided. Systematics of the spin Hamiltonian parameters b: and bz, as functions of the host-ion radius, are also studied.Les donnbs de RPE en bande X, recueillies Q. tempbrature ambiante sur les bchant.illons d'ion Gd3+ dopant monocristaux de hexahydrate de trichloride de terre-rare, ont btb analyshes utilisant une mbthode rigoureuse des moindres carrhs. Une discussion des trois formes des Hamiltonians de spin correspondant it trois orientations de C,, l'axe de symhtrie Q. double rotation, parallele aux axes magn6tiques X, Y, I; est inclue. On a trouvb que, pour C, I I Y, une valeur bien plus basse de x2, representant la qualit4 d'adaptation, est obtenue. Une discussion de la determination de degrb de monoclinicit4 comme revelhe par les parametres de I'Hamiltonian de spin, est inclue. Les systematiques des parametres b: et b$ de I'Hamiltonian de spin, comme fonctions du radius de I'ion-h&, sont aussi etudi&s.

Low temperature EPR spectra of Fe3+ centers in ternary layered TlGaS2 crystal

“…where g is the spectroscopic splitting tensor (g-factor), µ B is Bohr magneton, B is the applied magnetic field, S is the effective spin operators, and [10,11]. At this point, the cubic terms in the spin Hamiltonian can be neglected since, as it is shown in [9], they are very small comparing with very strong second order terms in this crystal.…”

“…For analyzing the low temperature EPR spectra of Fe doped TlGaS 2 , an effective spin Hamiltonian consisting of Zeeman electronic (Z) terms and ZFS terms expressed in extended Stevens (ES) operator notation [10] can be employed:…”

Reanalysis of crystal field parameter datasets for rare-earth ions at low symmetry sites: Nd3+ in NdGaO3 and Pr3+ in PrGaO3

“…C 2 ||z, C 2 ||y, and C 2 ||x [8,9,28,29]. The implications of these choices are: (i) each choice yields a completely different form of the CF Hamiltonian [8,9] and (ii) for each choice there exists an infinite number of physically equivalent but different CFP datasets [8,9,28,29]. A specific CF Hamiltonian form suitable for the choice C 2 ||z has been used in [1] without justification rendering the resulting CFP dataset unreliable.…”

“…Depending on symmetry, different pairs (B q k , B −q k ) can be selected for fittings [9,26]. For monoclinic symmetry [8,[28][29][30], e.g., B 2 2 and B −2 2 cannot be determined independently [9]. Hence the statement [3]: "fifteen independent CEF parameters" and that regardingB 0 2 , B 2 2 , B −2 2 , B 0 4 , and B 0 6 as five independent CFP's are not valid.…”

Low-Symmetry Aspects in EPR Spectra of Mn2+at Bi3+Sites in BiVO4Single Crystal

“…Tw o other equivalent forms of monoclinic ZFS Hamiltonian should be considered if the magnetic axis x or y is chosen as parallel to the monoclinic C2 axis [27,28]. Standardization of orthorhombic [29,30] and monoclinic ZFS (as well as crystal field) Hamiltonian [27] should be considered if the experimental value of the ratio Β /4?…”