Moments Of Rare-earth Ions Research Articles

Magnetic Properties of REMe0.5Mn0.5O3(RE = Rare Earth Element, Me = Ni, Co)

Magnetic properties of REMe 0.5 Mn 0.5 O 3 with Me = Ni and Co are investigated for a series of rare earth (RE) elements. In both systems with Me = Ni and Co, the Curie temperature ( T C ), below which the magnetic moments of Me 2+ and Mn 4+ allign ferromagnetically, decreases remarkably as RE goes from La to heavier elements; from 295 K for RE = La to 50 K for Lu with Me = Ni, and from 250 K for La to 95 K for Ho with Me = Co. The decrease of T C is interpreted as due to the bond angle (θ) dependence of the superexchange interactions between Me 2+ and Mn 4+ through O 2- ; T C is roughly linear to cos 2 θ as predicted by a simple theory [C. Boekema et al. : Int. J. Mag. 3 (1972) 341], but a distinct deviation from the linear relation is observed for the late RE elements. The magnetic moments of RE ions appears only in a low temperature region, typically below 30 K. Qualitative discussion on the exchange interactions involving RE is presented.

Magnetoelastic contribution to thermal expansion of rare-earth zircons

Comparative analysis is performed for the magnetoelastic contributions to thermal expansion of two groups of rare-earth zircons: phosphates RPO 4 (R=Y,Tb–Yb) and vanadates RVO 4 (R=Pr, Nd, Gd–Yb). Significant magnetoelastic anomalies of thermal expansion are observed and magnetoelastic contributions are found in regard to the corrections for the changes of the phonon contributions throughout the series of RPO 4 and RVO 4. Magnetoelastic contributions to thermal expansion are demonstrated to be well accounted for by the temperature dependences of the quadrupole moments of rare-earth ions both in phosphates and vanadates. The fully symmetric magnetoelastic coefficients are determined for all the rare-earth compounds under investigation; they are of the same sign and comparable magnitude in vanadates and phosphates, whereas the magnetoelastic contributions are opposite in sign for two isomorphous groups of rare-earth zircons.

Virtual bound state contribution to the magnetic moment of an ion in a multilayered system

We discuss the influence of spatial inhomogeneities of the free electron density, generated due to interface effects, on magnetic properties of the system. We calculate the interface lateral lattice deformation, due to ionic radii misfit, within the Frenkel-Kontorova model and derive its influence on spatial variation of the free electron density. Further, we calculate the excess magnetic moment of rare earth ions, arising from the virtual bound state contribution.

Paramagnetic Susceptibility of Nonstoichiometric Fluorides with the Fluorite-Type Structure

Magnetic properties of single crystals of nonstoichiometric fluorides M1-xRx F2+x (M = Ca, Sr, Ba; R = Ce, Pr, Nd, Gd, Ho, Er, Tm, Yb; with 0.05 ≤ x ≤ 0.28) with the fluorite-type structure have been studied for the first time. The magnetic susceptibility was measured using a Faraday balance in the 15-300 K temperature range. The samples are paramagnetic following the Curie-Weiss law. The values of paramagnetic Curie temperatures and effective magnetic moments of rare-earth ions have been found. Deviations of the temperature dependence of magnetic susceptibility from the Curie-Weiss law are observed for some nonstoichiometric fluorides at temperatures ranging from 60 to 85 K. Possible reasons for these deviations are discussed. Measurements of magnetic susceptibility provide an effective technique for a rapid and accurate determination of the concentration of rare-earth ions in nonstoichiometric fluorides.

Crystal field and magnetic moments of rare-earth ions in REBa 2Cu 3O -x (RE=Ce,...,Yb)

The superposition model is used to predict the values of the fourth- and sixth-order crystal-field parameters and consequently also the nature of magnetic moments of rare-earth ions in superconducting orthorhombic phase of REBa 2Cu 3O 7-x(RE=Ce,...,Yb). A similarity between the coordination dodecahedra of rare-earth ions in REBa 2Cu 3O 7-x and garnets is used for this purpose. The low-temperature magnetic moments of rare-earth ions are anisotropic and partially quenched. The quantitative conclusions are in general hampered by strong dependence of the magnetic moments on the crystal-field parameters of second order. As the superposition model gives no useful prediction for these parameters, it will be necessary to determine them by fitting to suitable experimental data.

Spin Wave Spectra in A–Co2 Compounds

Spin wave spectra in A–Co 2 compounds, where A is a heavy rare earth element, are calculated in a combined model of itinerant d -electrons of Co and localized magnetic moments of rare earth ions.

Rare earth ions in a hexagonal field III

Energy levels, eigenfunctions and magnetic moments of rare earth ions in a crystal field of hexagonal symmetry have been obtained using a Hamiltonian of the form, H = μBgJ · H +B40O40 + B60(O60 + 778 O66). Results are presented for all J values appearing in the rare earth series and for values of the parameters covering the situations in which the crystal field interaction is dominant, in which the interaction with the magnetic field is dominant and in which the two interactions are comparable in magnitude.

Rare earth ions in a hexagonal field. II

Energy levels, eigenfunctions and magnetic moments of rare earth ions in a crystal field of hexagonal symmetry have been obtained using a Hamiltonian of the form, H = μ B gJ · H + B 4 0 O 4 0 + B 6 0( O 6 0 + 77 8 O 6 6) . Results are presented for all J values appearing in the rare earth series and for values of the parameters covering the situations in which the crystal field interaction is dominant, in which the interaction with the magnetic field is dominant and in which the two interactions are comparable in magnitude.

Rare-earth ions in a hexaognal field I

Energy levels, eigenfunctions, and magnetic moments of rare-earth ions in a crystal field of hexagonal symmetry have been obtained using a Hamiltonian of the form H = B 4 0 O 4 0 + B 6 0( O 6 0 + 77 8 O 6 6 ). Results have been presented for all J values appearing in the rare-earth series and have been tabulated in a form convenient for use in analyzing the influence of the crystal field on the bulk thermal and magnetic properties of compounds containing the rare earths. Since experiment shows that B 6 0 B 6 6 may deviate from 8 77 , a few calculations were made with this ratio deviating by 10 and 20% (from 8 77 ). These calculations showed the results to be relatively insensitive to changes in B 6 0 B 6 6 .