Magnetic properties of the rare-earth ferroborate SmFe3(BO3)4

The magnetic properties of trigonal antiferromagnet SmFe₃(BO₃)₄ are studied experimentally and theoretically. The measured characteristics are considered in terms of a theoretical approach based on the molecular field approximation and a crystal field model for a rare-earth ion. The temperature dependences of the initial magnetic susceptibility and the field and temperature dependences of magnetization in fields up to 5 T are described, and the anomaly in the magnetization curve for B ⊥ c near 1 T, which points to a first-order phase transition, is analyzed.     

Magnetic properties of Y(Fe0.95Mn0.05)2 compound

Mössbauer spectroscopy, magnetization and X-ray diffrraction measurements of the ternary compound Y(Fe_0.95Mn_0.05)₂ prepared by melting were performed in order to investigate the effect of the substitution of Mn on the magnetic properties of YFe₂. The experimental results show change of the lattice parameter. The magnetization and the Curie temperature decrease with substitution of Fe by Mn.     

Comparison of the Absorption Spectra of Nd3+ Ions in the NdFe3(BO3)4, Nd0.5Gd0.5Fe3(BO3)4, and Ho0.75Nd0.25Fe3(BO3)4 Crystals

Physics of the Solid State - The polarized optical absorption spectra in the region of a series of the f–f  transitions of Nd3+ ions in the Ho0.75Nd0.25Fe3(BO3)4,...     

Crystal field effects in rare-earth ferroborates RFe3(BO3)4 with R = Nd, Tb, Dy, or Er

Crystal field effects in rare-earth ferroborates RFe₃(BO₃)₄ with various rare-earth elements are studied theoretically. The rare-earth magnetoelastic interaction Hamiltonian is written in a multipole approximation. The field and temperature dependences of the multipole moments and strain susceptibilities of rare-earth ions in the ferroborate structure are calculated. A comparative analysis of anomalies in the thermal expansion and elastic constants of rare-earth ferroborates with Tb and Dy ions having identical magnetic structure but differing in the degree of anisotropy of the rare-earth ion is performed.     

Magnetic properties of HoFe3(BO3)4

The magnetic properties of an antiferromagnet with trigonal symmetry, namely, HoFe₃(BO₃)₄, have been investigated theoretically. The calculations have been performed in the molecular field approximation and in the framework of the crystal field model for the rare-earth subsystem. Extensive experimental data on the magnetic properties of HoFe₃(BO₃)₄ have been interpreted and good agreement between theory and experiment has been achieved using the obtained theoretical dependences. The spontaneous spin-reorientation transition and the spin-reorientation transition induced by a magnetic field B ‖ a from the easy-axis to easy-plane state, as well as the spin-flop transition in a magnetic field B ‖ c, have been described. It has been shown that the spontaneous spin-reorientation transition is a magnetic analog of the Jahn-Teller effect. The temperature dependences of the initial magnetic susceptibility at temperatures ranging from 2 to 300 K, the nonlinear curves of magnetization for B ‖ c and B ⊥ c in a magnetic field up to 1.2 T (which indicate the occurrence of first-order phase transitions), and their evolution with variations in the temperature have been described, as well as the temperature and field dependences of the magnetization in a magnetic field up to 9 T. The parameters of the trigonal crystal field for the rare-earth ion Ho³⁺ and the parameters of the Fe-Fe and Ho-Fe exchange interactions have been determined in the course of interpretation of the experimental data.     

Magnetic Properties of Sm0.7Ho0.3Fe3(BO3)4

The magnetic properties of a ferroborate single crystal of substituted composition Sm_0.7H_0.3Fe₃(BO₃)₄ with competing Sm-Fe and Ho-Fe exchange interactions are studied. The measured properties and effects are interpreted in terms of a general theoretical approach based on the molecular field approximation and calculations using the crystal field model for a rare-earth ion. The experimental temperature dependences of the initial magnetic susceptibility in the temperature range 2?C300 K, the anomalies in the magnetization curves for B ?? c and B ?? c in fields lower than 1.2 T, and the field and temperature dependences of magnetization in fields lower than 9 T are described. The crystal field parameters and the parameters of the R-Fe and Fe-Fe exchange interactions are determined during the interpretation of the experimental data.     

Spectroscopic investigation of rare-earth chromium borates RCr3(BO3)4 (R = Nd, Sm)

The optical absorption spectra of single crystals of neodymium and samarium chromium borates are studied. A magnetic phase transition in NdCr₃(BO₃)₄ (at T _c = 8 ± 1 K) and SmCr₃(BO₃)₄ (at T _c = 5 ± 1 K) is observed. The effective magnetic field acting on the Nd³⁺ ion from the side of the ordered magnetic subsystem of chromium is estimated.     

Infrared absorption spectra of a Nd0.5Ho0.5Fe3(BO3)4 crystal

Infrared absorption spectra of a Nd_0.5Ho_0.5Fe₃(BO₃)₄ crystal in the spectral range of 30–1700 cm^–1 have been measured at temperatures from 6 to 300 K. The experimental spectra have been analyzed based on the semiempirical calculation of the lattice dynamics and the analysis of correlation diagrams of borate complexes. No changes associated with structural phase transitions have been detected in the temperature range of measurements; the effect of magnetic ordering on the infrared absorption spectra has not been observed.     

Features of magnetic and magnetoelectric properties of rare-earth multiferroic PrFe3(BO3)4 with the singlet ground state

The features of magnetization of rare-earth multiferroic PrFe₃(BO₃)₄ with the singlet ground state have been investigated theoretically. The magnetic anisotropy of the crystal has been studied. The temperature dependences of anisotropy constants have been calculated. The phase H-T diagram has been constructed. The dependences of the behavior of magnetization vectors of magnetic sublattices on the external magnetic field have been obtained. The magnetoelectric effect has been investigated, and the dependences of polarization on the temperature and field have been found for its various orientations. The theoretical data have been compared with the experimental data and their good agreement has been established.     

Specific heat of YFe3(BO3)4, Y0.5Gd0.5Fe3(BO3)4, and GdFe3(BO3)4

The specific heat was measured in the range 0.4–300 K in YFe₃(BO₃)₄, Y_0.5Gd_0.5Fe₃(BO₃)₄, and GdFe₃(BO₃)₄ single crystals. Sharp anomalies were found at temperatures of first-order structural, second-order antiferromagnetic, and first-order spin-reorientational transitions. A Néel temperature of about 37 K was found to be virtually independent of presence of rare-earth ions, indicating rather weak coupling of Gd and Fe subsystems. The contribution of the magnetic system to specific heat was separated through the scaling procedure allowing determination of the magnetic entropy of Fe and Gd subsystems. At the lowest temperatures, the specific heat in GdFe₃(BO₃)₄ exhibits a Schottky-type anomaly, which is due to Gd³⁺ eightfold degenerate ground-level splitting by the internal magnetic field of the Fe subsystem of about 7 T. The text was submitted by the authors in English.     

Core level spectroscopy and RHEED analysis of KGd0.95 Nd0.05(WO4)2 surface

A study of the surface structure and electronic properties of (010) KGd_0.95Nd_0.05(WO₄)₂ (Nd:KGW) using RHEED analysis and XPS is presented. It is shown that Nd doping has a negligible effect on the core levels of the basic elements. A bombardment of the Nd:KGW crystal with 3-keV Ar ions results in surface amorphization accompanied by the generation of tungsten ions in lower valence states.     

Dy3+掺杂EuAl3(BO3)4晶体的荧光性质

制备了EuAl3(BO3)4晶体和Dy3+:EuAl3(BO3)4晶体，并且研究了它们的荧光性质．EuAl3(BO3)4晶体具有强的红光发射．在Dy3+掺杂的EuAl3(BO3)4晶体中，Dy3+对Eu3+的荧光有很强的敏化作用，提出了敏化作用的机制是能量的共振传递．Dy3+敏化作用的最佳掺杂浓度为0.2，高于0.2时，由于Dy3+的浓度焠灭效应，DyxEu1-xAl3(BO3)4晶体中Eu3+的613 nm发射峰强度急剧下降．     

Rietveld analysis and multiferroic properties of Fe doped Ba0.95Bi0.05TiO3 ceramics

We report on the structural, magnetic and ferroelectric properties of Fe doped Ba_0.95Bi_0.05TiO₃ (Ba_0.95Bi_0.05Ti_1−yFe_yO₃ (0 ≤ y ≤ 0.1)) ceramics prepared by solid state reaction. Rietveld analysis shows that compounds with y ≤ 0.07 have a single phase-tetragonal structure (space group P4mm), and the tetragonality (c/a) decreases as x increases. Ba_0.95Bi_0.05Ti_0.93Fe_0.07O₃ ceramic shows ferromagnetic order with a Curie temperature of about 700 K and ferroelectric order at room temperature. These results indicate that the Ba_0.95Bi_0.05Ti_0.93Fe_0.07O₃ can be useful as a multiferroic material.     

Intracavity frequency-doubled diode-pumped Nd : LaSc3(BO3)4 lasers

 An intracavity frequency-doubled 10%Nd : LaSc₃(BO₃)₄ (Nd : LSB) laser was investigated in different resonator configurations and in different operation modes under continuous wave (cw) and quasi-cw laser-diode pumping. With a Cr⁴⁺ : YAG passive modulator and a KTP crystal the second-harmonic output power at 531 nm amounted to 190 mW in Q-switched TEM₀₀ mode at 750 mW of pump power. In a sandwich resonator, when all the optical elements were in direct contact with each other, 0.8 W of green output power was obtained in cw mode under 2.7 W of pump power with a slope efficiency of 44%. In the same setup under fiber-coupled diode-laser array pumping (5.6 W of incident power), 1.2 W of green output power was achieved in cw mode and 1.4 W in quasi-cw mode. Received: 30 April 1996/Revised version: 1 July 1996     

Magnetic and Magnetoelectric Properties of Scandoborate NdSc3(BO3)4

Physics of the Solid State - Trigonal neodymium scandoborate NdSc3(BO3)4 single crystals have been grown by the batch flux method using bismuth trimolybdate and their magnetic and magnetoelectric...     

Linear electro-optic properties of YCa4O(BO3)3

We have characterized the effective linear electro-optic coefficients of YCa4O(BO3)3 (YCOB) relative to KH2PO4 and KD2PO4 at 632.8 nm. We measured a maximum r(eff) value of 10.8 +/- 1.4 pm/V for YCOB in a transverse electric field configuration for propagation along the X or the alpha dielectric axis, with the electric field applied along the Z or the gamma dielectric axis. We also found effective coefficients of 10.7 +/- 1.0 and 3.4 +/- 0.4 pm/V for YCOB in longitudinal configurations. The remaining values of r(eff) for various transverse applied voltages were found to be less than 3 pm/V. The excellent thermomechanical properties of this crystal, coupled with moderate electro-optic coefficients, make YCOB and its isomorphs potential candidates for use as high-average-power electro-optic switches.     

Structural and magnetic properties of bulk and thin films of Mg0.95Mn0.05Fe2O4

We present here a comparative study on structural and magnetic properties of bulk and thin films of Mg_0.95Mn_0.05Fe₂O₄ ferrite deposited on two different substrates using X-ray diffraction (XRD) and dc magnetization measurements. XRD pattern indicates that the bulk sample and their thin films exhibit a polycrystalline single phase cubic spinel structure. It is found that the film deposited on indium tin oxide coated glass (ITO) substrate has smaller grain size than the film deposited on platinum coated silicon (Pt–Si) substrate. Study of magnetization hysteresis loop measurements infer that the bulk sample of Mg_0.95Mn_0.05Fe₂O₄ and its thin film deposited on Pt–Si substrate shows a well-defined hysteresis loop at room temperature, which reflects its ferrimagnetic behavior. However, the film deposited on ITO does not show any hysteresis, which reflects its superparamagnetic behavior at room temperature.     

IR spectroscopy of rare-earth aluminum borates RAl3(BO3)4 (R = Y,Pr-Yb)

Rare-earth aluminum borates RAl₃(BO₃)₄ (R = Y, Nd-Yb) obtained by spontaneous high-temperature flux crystallization form two polytype modifications described by the space groups R32 (D ₃ ⁷ ) and C2/c (C _2h ⁶ ). They differ in the symmetry versions in mutual arrangement of layers. These borates have been investigated by mid- and far-IR spectroscopy in combination with factor-group analysis of the vibrations of BO ₃ ^3? ions; translational motions of Al³⁺, R³⁺ (Y, Nd-Yb), and BO ₃ ^3? ions; and BO ₃ ^3? rotations. Rare-earth aluminum borates are assigned to different space groups according to their IR spectra. Borates with large rare-earth Nd and Pr cations are crystallized into the space group C2/c (C _2h ⁶ ), while borates with smaller (Y, Sm-Yb) ions are crystallized into the space group R32 (D ₃ ⁷ ). The rhombohedral structure of the latter compounds includes monoclinically ordered domains, as is evidenced by the presence of monoclinic-phase bands in the IR spectrum. NdAl₃(BO₃)₄ and SmAl₃(BO₃)₄ can form both monoclinic and rhombohedral polytypes. The IR spectrum of the monoclinic SmAl₃(BO₃)₄ phase contains bands due to the rhombohedral phase, while the IR spectrum of NdAl₃(BO₃)₄ (which is described by the space group R32) contains bands due to the monoclinic polytype. The presence of domains with another arrangement of layers in the polytype structure is a characteristic sign that corresponds to the order-disorder theory; this theory explains the structure of polytypes.