Papers by Keyword: Crystal Field Parameters

Abstract: A method of measuring crystal field parameters by means of a rotating-sample magnetometer is presented. The measurement is performed by registering 2nd, 4th and 6th harmonics of the signal that is proportional to magnetization change due to rotation of the sample in a magnetic field. Experimentally measured temperature dependence of the amplitudes of these harmonics is used to determine the crystal field parameters within the framework of the theoretical model proposed in [. The signal is detected by a digital lock-in amplifier, while temperature is controlled by a PID controller. The sample and pickup coils are located in the bore of a Halbach permanent magnet. The measurements are fully automated. Magnitude of the expected signal was estimated. Test measurements of magnetization of the Tb single crystal along a axis (in the easy crystallographic plane a-b) in the permanent magnetic field 2.7 T at room temperature were performed. The results show that sensitivity of the instruments and the proposed design of the equipment allows us to determine crystal field parameters of heavy rare-earth metals. Testing of the control software showed that computer-device communications and execution of the software blocks are correct.

Abstract: Tungsten-phosphate glasses doped with trivalent europium ion are synthesized and their spectroscopic properties are analyzed. Following the evolution of the 5D0 → 7F1 electronic transition in a series of various glass compositions via two rank crystal field parameters (cfp’s), a slight modification of the local symmetry is evidenced in the series. Decay lifetimes of 5D1 and 5D0 levels are also analyzed. Optical properties clearly correspond to Eu3+ in the glassy phase. At room as well as at liquid nitrogen temperatures, the emission spectra display comparable features with prominent 5D0 → 7F2 transition. However, at 77 K, the maximum 7F1 splitting exhibits an increase of ≈ 20-23 % for all compounds. This increase is directly connected to a change in local environment around the rare earth ion. The optical properties and the crystal field variation could be correlated with the shortness of the metal-oxygen distances produced by the pressure when cooling.