Room temperature magnetization measurements of some substituted rare earth iron garnets

The saturation magnetization (M _s) and the initial magnetic susceptibility (χ _in) of substituted yttrium iron garnet (YIG) Ho_3−x Y _x Fe₅O₁₂ where (x=0,0.3,1.5), pure terbium iron garnet Tb₃Fe₅O₁₂, and substituted aluminum iron garnet (AlIG) Ho₃Fe_5−x Al _x O₁₂ where (x=0.05,0.7) at room temperature are reported. It has been observed that M _s and χ _in decrease in a linear manner as Ho³⁺ replaces Y³⁺ in yttrium iron garnet. For substituted (AlIG), a drastic decrease in both M _s and χ _in as Al³⁺ ions replace Fe³⁺ ions. The rate of decrease of M _s and χ _in with the increase of Al³⁺ for substituted (AlIG) is greater than that for substituted (YIG). That is attributed to the decrease in the superexchange interaction (self and mutual iron interactions) with Al substitution.     

Magnetic properties of some rare earth tellurate garnets

The magnetic properties of the lanthanide tellurate garnets Ln₃Te₂Li₃O₁₂ for Ln=Pr, Nd, Gd-Er, and Yb are found to exhibit similarities in many cases to the related aluminum or gallium garnet compounds. Magnetic exchange is also roughly comparable in magnitude, despite the systematic difference in exchange pathways.     

Magnetic properties of rare earth iron borates: Spectroscopic investigation by the method of rare earth probe

The magnetic phase transitions and magnetic structures in RFe₃(BO₃)₄ (R = Y, Gd-Er) iron borates have been investigated by the method of erbium spectroscopic probe. The magnetic ordering temperatures have been determined. On the basis of the comparison of the character of splitting of the spectral lines of the probe Er³⁺ ion in RFe₃(BO₃)₄(R = Y, Dy-Er) iron borates and in GdFe₃(BO₃)₄, a complicated whose magnetic structure is known, a conclusion is drawn about the orientation of the magnetic moments of iron: in dysprosium and terbium iron borates, an easy-axis magnetic structure is implemented, whereas an easy-plane structure occurs in holmium, erbium, and yttrium iron borates.     

Magnetization measurements on some rare-earth iron garnets

The magnetic properties of Fe-based singlecrystal garnets have been studied. A magnetic field up to 55 kOe in the temperature range from 4.5 to 300 K has been used. The compensation temperature (T _comp) of the studied garnets has been determined. The compensation temperature increases with the increase of the rare-earth ions (Ho³⁺ or Gd³⁺) substituting Y³⁺ ions in thec sublattice of R₃Fe₅O₁₂. AboveT _comp, the magnetization was found to be linearly field dependent. The results are in good agreement with magnetization measurements performed on polycrystaline samples, and with calculations based on the crystal field parameters of the isostructural Holmium Gallium Garnet (HoGG).     

Scattering of acoustic phonons by rare earth substitutional atoms in yttrium aluminum garnets

The diffusive maxima of phonon signals, and in particular their arrival timest _m are examined for a number of solid solutions of rare earth atoms in yttrium aluminum garnets. The phonon pulses are generated by metallic films of the characteristic lengthl _h heated by current pulses to the temperatureT _h slightly higher than the ambient temperatureT. The injected phonons travel in wafers of the thicknessL _z. They are scattered by substitutional atoms of rare earth occupying the yttrium dodecahedral sites, rare earth and yttrium atoms occupying the aluminum octahedral sites and by another lattice imperfections generated in the process of sample growing. The qualitative analysis based on our exact formula for the diffusion coefficientD allows us to extract the contribution of rare earth atoms substituting the Y atoms toD. Considering the dependence oft _m/L _z ² on the temperature and the ratiol _h/L_z we conclude thatD～T _h ^?4 and that the energy of phonons forming the diffusive maxima ranges from 3.2k _BT_H to 4.2k _BT_H, which is in reasonable agreement with the existing estimates.     

Scattering of acoustic phonons by rare earth substitutional atoms in yttrium aluminum garnets

The diffusive maxima of phonon signals, and in particular their arrival timest _m are examined for a number of solid solutions of rare earth atoms in yttrium aluminum garnets. The phonon pulses are generated by metallic films of the characteristic lengthl _h heated by current pulses to the temperatureT _h slightly higher than the ambient temperatureT. The injected phonons travel in wafers of the thicknessL _z. They are scattered by substitutional atoms of rare earth occupying the yttrium dodecahedral sites, rare earth and yttrium atoms occupying the aluminum octahedral sites and by another lattice imperfections generated in the process of sample growing. The qualitative analysis based on our exact formula for the diffusion coefficientD allows us to extract the contribution of rare earth atoms substituting the Y atoms toD. Considering the dependence oft _m/L _z ² on the temperature and the ratiol _h/L_z we conclude thatD∼T _h ⁻⁴ and that the energy of phonons forming the diffusive maxima ranges from 3.2k _BT_H to 4.2k _BT_H, which is in reasonable agreement with the existing estimates.     

X-ray isochromats of some rare earth elements

Recordings of the isochromat curves of the rare earth elements 64 Gd to 71 Lu have been made by means of a high vacuum spectrometer provided with a bent topaz crystal. The information concerning the density of statesN(E) near the Fermi limit is compared with that deduced from specific heat measurements. The results obtained from the isochromat curves are rather constant, which on account of the atomic configuration in these elements is expected. An observed anomaly in the band structure of Tb metal is discussed. The appearance of this anomaly indicates that a rigid band model is not applicable to some of the actual elements.     

Dependence of crystal field in rare earth garnets on the structure of coordination dodecahedron

The superposition model is used to relate the crystal field parameters reported in various rare earth garnets to the structure of the coordination dodecahedron. The results obtained confirm the overall consistency of the model, reported by other authors, but they differ in the dependence of intrinsic parameters upon distance. Special attention is paid to the approximations inherent to the procedure and to the utility of the model in quantitative predictions.     

Spectroscopic investigation of iron ions in soda-tellurite glasses

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 52, No. 3, pp. 434–438, March, 1990.     

On the magnetic arrangement in the diamagnetically substituted rare earths iron garnets

The magnetic arrangement in the rare earth iron garnet with diamagnetic substitution in octahedral sites, at 0 K, is calculated on the basis of the model of localized canting, when the exchange interaction between rare earth and iron ions is taken into account. The magnetization measurements on scandium substituted gadolinium iron garnet and neodymium iron garnet are reinterpreted.     

Preparation and investigation of rare earth magnesium hexaaluminate solid solutions

Conditions of preparation, by the method of solid state reactions, of rare-earth hexaaluminates RE_1?x?yM_xM’_yMgAl₁₁O₁₉ (RE = La, Sm; M, Mt’ = Gd, Yb, Lu, Y, Sc; x, y = 0, 0.15, 0.3), were investigated. For a number of compositions, high-degree single-phase products were obtained applying multi-step heat treatments in Ar/H₂ atmosphere at 1650–1690°C. Intense (107) and (114) diffraction lines typical for the hexaaluminate phase have been observed in X-ray diffraction patterns. Studies of microstructure and of elemental composition showed that magnesium deficiency on the sample surface may reach some 20%, while composition in the bulk is more homogeneous and close to stoichiometric. Our estimations of structural homogeneity and thermal conductivity show that lanthanum hexaaluminates La_1?x?yM_xM’_yMgAl₁₁O₁₉ with pair additives Gd-Yb, Gd-Y, Y-Yb, Y-Lu, Y-Sc (x = y = 0.15) and samarium hexaaluminates Sm_1?x?yM_xM’_yMgAl₁₁O₁₉ with pair additives Gd-Yb, Y-Yb (x = y = 0.15), as well as Sm_0.7Yb_0.3MgAl₁₁O₁₉, may present interest as thermal barrier coatings.     

Magnetic and transport properties of some light rare earth tungstates

Measurements relating to molar magnetic susceptibility, dc electrical conductivity and thermoelectric power of Nd, Sm, Eu and Gd are reported. The ac electrical conductivity at a few temperature ranges is also given. It is found that it follows the Curie-Weiss law behaviour and this has been attributed to the crystal field effect. The experimental value of Bohr magneton for the magnetic ions has been found to be in good agreement with theory. Thermoelectric power is negative in the measured temperature range suggesting these materials to bep-type semi-conductors and holes as the dominant charge carriers. The results are explained using band theory.     

Magnetic properties and spin reorientation of iron rare earth based intermetallics

The Curie temperature and saturation magnetization M_s(μ_B/f.u.) of R₂Fe₁₄B have been discussed. The spin reorientations of Nd₂Fe₁₄B compounds have been studied by many authors with various methods, but have not been checked with the neutron diffraction method. We investigated the spin reorientation of Nd₁₅Fe₇₈B₇ by neutron diffraction and obtained θ = 26°34' at 77 K which is in good agreement with other authors' results. The small amount substitution of Si for Fe in Nd₂(Fe_1−xSi_x)₁₄B increases T_c and _cH_c of the compound. These will be able to make an advantage for Nd-Fe -B magnets.     

Concentration dependence of the Fe moments in rare earth iron compounds

A linear relationhip has been found between the hyperfine fields observed at the various Fe sites in rare earth iron compounds R_xFe_y and the relative number of near neighbour Fe atoms corresponding to these sites. From these results it is concluded that the concentration dependence of the magnitude of the Fe moments in these compounds is largely determined by the local environment.