Effects of O ions beam irradiation on crystal structure of rare earth sesquioxides

We report the results of ion irradiation influence on rare earth sesquioxides structure, which are materials of practical importance as a radiation resistant ceramics in nuclear applications. Y₂O₃, Gd₂O₃ and Er₂O₃ sesquioxides in the pellet form were irradiated by oxygen ions (O²⁺) beam with the energy of 30 keV and implantation fluence of 5 × 10²⁰ m⁻². Samples are characterized by Grazing Incidence X-ray Diffraction (GIXRD), Raman spectroscopy and atomic force microscopy (AFM). By GIXRD it was found partial transformation from cubic (C) to monoclinic (B) phase only in Gd₂O₃, induced by O²⁺ irradiation. This was confirmed by Raman spectroscopy. Although full phase transition from C to B phase in Y₂O₃ was not observed, the splitting and broadening of the main intensity Raman band for C phase could be explained by the stress and the disorder induced by the quenching. Analysis done by AFM showed changes in surface topology, i.e. values of average roughness (Ra) and root mean squared roughness (RMS) were significantly changed after irradiation for all samples. RMSs in Y₂O₃ before and after irradiation were 35 nm and 26 nm, respectively.     

Exhibition of surface steps by high resolution electron microscopy of monoclinic rare earth sesquioxides

On high resolution structure images, the existence of a superperiod has been observed, linked with the apparition of extraspots in the diffraction diagram. The specimen (B-Sm₂O₃) can be described as composed of layers of thickness 6 Å, nearly perpendicular to the incident electron beam. These layers are of 3 different kinds. We have shown that the apparition of the superperiod can be linked with steps of height 6 or 12 Å (i.e. 1 or 2 layers): computed images, using this hypothesis exhibit the observed superperiod, even for thicknesses around 230 Å. This allows atomic steps to be imaged with a high resolution structure image.     

Coriolis attenuation in the rare earth region

It is shown that the observed rotational band structure in a number of odd-proton and odd-neutron nuclei situated in the rare earth region, can be reproduced in the particle-rotor model without any ad hoc reduction of the Coriolis matrix elements if a value of the pairing gap parameter, which is about 30–40% of that deduced from the corresponding odd-even mass difference, is used. The importance of the proper choice of the pairing gap parameter in the study of the Coriolis attenuation problem is emphasised.     

稀土矿区茶叶稀土元素ICP—AES测定

本文用ＩＣＰ－ＡＥＳ测定稀土矿区茶叶中元素，并用干扰素数法校正茶中的无机元素及其他稀土元素对待测稀土元素的光谱干扰，在最佳工作条件下，测定了茶叶样品中的稀土元素含量。     

Magnetic rare earth superlattices

Advances in molecular beam epitaxy deposition techniques have recently made it possible to grow, an atomic plane at a time, single crystalline superlattices composed of alternating layers of a magnetic rare earth, such as Gd, Dy, Ho, or Er, and metallic Y, which has an identical chemical structure. The primary goal of this article is to review the new and interesting magnetic structures which have been discovered in these novel superlattice systems and to consider what implications the observed phases have on our understanding of the underlying microscopic magnetic interactions. In particular, the effects of the artificial periodicity or compositional modulation, finite layer thickness, and epitaxial strain on the resulting long range magnetic order of Gd-Y, Dy-Y, Ho-Y, Er-Y, and Gd-Dy superlattices are described.     

Transport anomalies in dilute silver-rare earth alloys

It is noted that the residual resistivities for Ag alloyed with rare earth impurities from the latter half of the rare earth series are approximately three times the residual resistivity for any other trivalent impurity. Moreover, these residual resistivities are essentially independent of the magnetic character of the impurities. New thermoelectric power data indicate the impurity contributions to the diffusion thermoelectric power are positive. These anomalies are shown to be consistent with a very simple model which includes core contributions to the seattering.     

Superexchange interaction in rare earth dielectrics

The second quantization method is applied to the analysis of superexchange interaction in rare earth dielectrics. Introduction of double tensor operators associated with the second quantization operators makes it possible to write the superexchange interaction Hamiltonian in the effective form of the total magnetic moment interaction of ions . As an example, the obtained Hamiltonian is used to explain the magnetic properties of rare earth pnicudes of the yttrium group.Translated from Izvestiya VUZ. Fizika, No. 12, pp. 78–82, December, 1973.The authors thank B. V. Karpenko and V. Ya. Mitrofanov for useful discussions.     

Intermediate valence in rare earth systems

The current status of the phenomenon of intermediate valence in rare earth systems is surveyed. Particular attention is paid to the merits and demerits of various experimental methods employed to obtain the value of the mean valence of the rare earth ion, followed by the discussion on the cerium problem.     

Magnetoelastic interaction in rare earth systems

A theory of rotationally invariant spin-lattice interactions in rare earth systems is presented. It is shown that rotational invariance to leading order is ensured only if rotational interactions of first and second order in the displacements are included simultaneously in the spin-lattice Hamiltonian. The rotational second-order interactions yield effects which are as large as those of the linear rotational interaction. It is pointed out that a corresponding statement should hold also for pure strain interactions.The phonon Green's function is calculated for the paramagnetic phase of rare earth systems. It is found that in an applied magnetic field the rotational interactions cause measureable changes of the phonon dispersion and the sound velocity even for cubic symmetry. These effects turn out to be of the same order of magnitude as the conventional field-dependent strain effects and are qualitatively different from the latter. The results of our theory are illustrated by the example of SmSb, and quantitative predictions for the transverse sound velocities are given.     

Effective crystal fields in the rare earth pnictides

Various contributions to the effective 4f electron crystal fields in the rare earth pnictides are estimated and compared. These include the direct interaction with the ligand electrostatic field and effects associated with the 5d band electrons.     

Magnetic properties of the rare earth pnictides

The magnetic properties of the binary rare-earth compounds with the nitrogen-group elements are briefly discussed, emphasizing the NaCl-type phases, for which the main magnetic data are collected.     

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.     

Growth-induced site preferences in rare earth garnets

A recent ECR experiment has provided experimental verification of the theoretically-predicted growth-induced non-random distribution of rare earth ions in flux-grown garnets. We show that the observed site preferences are in good agreement with the predictions of the site models proposed for the magnetically noncubic garnets.     

Magnetic dipole response in rare earth nuclei

Experimental observations in certain rare earth nuclei have established the presence of sizeable B(M1) strength of two peak structure lying in the 5–10 MeV region. The character of the states concerned, studied within a self-consistent Random Phase Approximation using Skyrme forces, are identified to be that of proton and neutron giant spin-flip resonances. Received: 14 July 1997 / Revised version: 20 October 1997     

Phase changes in cubic rare earth crystals

An explanation is offered of the structural transitions and magnetic orderings in the cubic rare earth compounds LnX with particular emphasis on the anomalous spin arrangements observed in HoP, DyP and DyAs and in ErSb and ErP.     

On the structural phase transition in rare earth elpasolites

The structural phase transition in two representatives of the rare earth elpasolite fluorides, Rb₂NaHoF₆ and Rb₂NaTmF₆, are studied in detail. The symmetry of the soft mode is determined from Raman spectra, X-ray and neutron powder diffraction data to be ₄ ⁺ . From the temperature dependence of the elastic constants of both compounds, estimates of various phase transition parameters are given, e.g. strain soft mode coupling constant and soft mode frequency. The softening of the elastic constants forT>T _c is explained by the strain coupling to the fluctuations of the soft mode coordinates. The energy of the soft phonon at the zone boundary is estimated from the data and compared with that of K₂ReCl₆. The phase transition mechanisms in rare earth elpasolites and hexahalometallates are discussed.     

Neutron strength functions in rare earth nuclei

The coupling of the single particle motion of the neutron to other degrees of freedom is studied by the (d, p) reaction leading to highly excited states in rare earth nuclei. Experimental spectra have been obtained with a telescope counter system for 13 rare earth isotopes of Gd, Dy, Er and Yb. The results are compared with calculations based upon the single particle model in a deformed Saxon-Woods potential. The spreading of the single particle strength resulting from the coupling to other degrees of freedom is taken into account in a simple phenomenological way. A qualitative similarity between the experimental and calculated spectra is observed, and the total integrated (d, p) cross section up to the neutron binding energy is reproduced quite closely by the calculations. For a given excitation energy, the amount of structure in the experimental spectrum seems to decrease with neutron number for each element investigated.     

Magnetoelastic coupling in dilute rare earth alloys

A model for coupling between Rare Earth ion and the lattice via conduction electrons is presented. It should be useful in explaining large magnetostriction effects in rare earth metals and their alloys.