M. Barański

Growth and properties of potassium holmium double tungstate KHo(WO4)2

Potassium holmium tungstate KHo(WO 4 ) 2 crystal, as other tungstates, shows the high temperature irreversible structural phase transition. Owing to this, KHo(WO 4 ) 2 single crystals were grown due to spontaneous crystallisation with use of the High Temperature Solution Growth technique, which allows to lower the temperature of crystallisation below the temperature of the phase transition. K 2 W 2 O 7 was used as a solvent. It provides a very wide temperature range of crystallisation and does not introduce additional impurities into the melt. The starting flux contained 20 mol% of KHo(WO 4 ) 2 dissolved in K 2 W 2 O 7 . It was found that potassium holmium double tungstate is pleochroic. The two different optical spectra: one spectrum for electrical vector of linearly polarised light parallel to optical Y axis (main spectrum) and second one for electrical vector perpendicular to Y axis were measured.

Crystal Growth Of Mixed Titanium Sillenites

(BGaO) single crystals have been grown, oo. Thermal conditions enabling growth oft uniform [110] sillenite single crystals with totally flat (110) interface have been found. Influence of composition on spectral characteristics of the BTO mixed crystals has been investigated. Keywords: sillenites, BTO, top seeded solution growth, optical absorption (Received November 6, 2002; Accepted May 14, 2002)

The magnetic properties of potassium holmium double tungstate

The magnetic investigations of potassium holmium double tungstate KHo(WO4)2 have been performed. The results of measurements of magnetic susceptibility and magnetization as a function of temperature (T from 0.3 K up to 100 K) and magnetic field (up to 1.5 T) are presented. A strong anisotropy of magnetic properties was found. The magnetic measurements data were used to calculate the interaction energy. It was shown that the interactions between nearest neighbors Ho3+ ions have antiferromagnetic character.

The low temperature magnetic properties of potassium holmium double tungstate

The magnetic investigations of potassium holmium double tungstate KHo(WO4)2 have been performed. The results of measurements of magnetic susceptibility and magnetization as a function of both temperature (T = 0.5–100 K) and magnetic field (up to 2 T) are presented.

Crystal growth and optical properties of iron sillenite Bi25FeO40

Top Seeded Solution Growth (TSSG) technique has been used to produce Bi25FeO40 (BiFeO) single crystals. Thermal conditions enabling growth of uniform [110] sillenite single crystals with flat (110) interface have been found. Spectral characteristics of these single crystals have been investigated. The optical absorption measurements were performed in a broad spectral (IR, VIS and UV) and temperature (3.5 K - 500 K) ranges. The intense source of light was used for coloration of samples. The thermally bleached state was reached after 2 hours annealing at 200°C in the darkness. The optical absorption spectra were shown to be connected with forbidden transitions of Fe3+ ions. The induced absorption is probably due to the polaron center (Fe3++h) similar to that observed in BGO and BSO single crystals.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Magnetic phase transition in KGd(WO4)2 double tungstate

Investigations of the specific heat of the potassium gadolinium double tungstate KGd(WO4)2 have been performed over the temperature range from 0.05 K up to 4 K in zero magnetic field. The λ -type anomaly observed at T = 0.42 K was interpreted as an indication of a second order magnetic phase transition within the Gadolinium sublattice. The critical exponent α was determined from experimental data.

The specific heat of potassium holmium double tungstate

The results of measurements of thermal properties (specific heat) of potassium holmium double tungstate KHo(WO4)2 as a function of temperature (from 0.5 to 300 K) and magnetic field (up to 2 T) are presented. The total specific heat without the phonon and Schottky contributions is found to have the anomaly with maximum at T SPT ∼ 5 K. This anomaly is likely related with the structural phase transition (SPT) caused by the cooperative Jahn–Teller effect. The increase of specific heat at very low temperatures and its shift towards high temperatures with increasing magnetic field are observed. The origin of this behaviour can be connected with possible magnetic phase transition induced by magnetic field.

Optical properties of potassium erbium double-tungstate KEr(WO4)2

Results of spectroscopic investigations of crystalline potassium-erbium double tungstate Ker(WO4)2 are reported. The single crystal of Ker(WO4)2 were grown by Top Seeded Solution Growth technique. They belong to the chain-layered group of materials crystallizing in monoclinic syngony. The investigations were carried out in the broad spectral and temperature range. It was found that the potassium erbium double tungstate belong to the class of the diaxial crystals and it is a pleochroic. The main optical absorption spectra are determined.

Magnetic Properties of the RbNd(WO₄)₂ Single Crystal

The magnetic investigations as a function of temperature and magnetic field for the rubidium neodymium double tungstate RbNd(WO4)2 single crystal have been performed. The magnetization was measured in the temperature range from 4.2 to 100 K and for the magnetic field up to 1.5 T. The crystal field and exchange parameters were found.