Spin-Lattice Relaxation in Pure and Europium-Doped BaF2 Crystals at High and Low Temperatures
Document Type
Article
Publication Date
12-1-1968
Description
The spin-lattice relaxation time T1 of F19 has been measured in a pure BaF2 crystal over a temperature range of 300 to 1150°K and in a BaF2 crystal containing 4.9×1019 ions/cm3 of Eu3+ from 4.2 to 1000°K. The measurements were made at 29 MHz using the magnetic-recovery method with the magnetic field along the [111] and [100] crystallographic directions. The electronic relaxation time τe of the europium was also measured at 9.5 gHz at 4.2, 63, 77, and 90°K. The data indicate that the diffusion of F- ions provides the predominant relaxation mechanism above 700°K in the pure sample and above 500°K in the doped one. The minimum in the high-temperature segment of the T1-versus-T curve appears at 990°K for pure BaF2 and at 800°K for doped BaF2. These yield jump frequencies of νF(vacancy)=1.3×1015exp(-1.35eV/kT) and νF(interstitial)=6.5×1011exp(-0.62eV/kT); to our knowledge these have never been measured before. Below 500°K the nuclear relaxation is due to paramagnetic impurities. The orientation dependence of T1 indicates that the transition from "diffusion limited" (DL) to "rapid diffusion" (RD) relaxation occurs between 50 and 70°K in the doped sample. In the DL range, we find good agreement between the observed T1 of F19 and the T1 values calculated from τe, whereas at 4.2°K, which lies in the RD range, the calculated value is 300 times larger than the observed one. Our low-temperature T1 data yield 5.6×10-14 cm/sec for the spin-diffusion constant D.
Citation Information
Miller, J. R.; and Mahendroo, P. P.. 1968. Spin-Lattice Relaxation in Pure and Europium-Doped BaF2 Crystals at High and Low Temperatures. Physical Review. Vol.174(2). 369-376. https://doi.org/10.1103/PhysRev.174.369 ISSN: 0031-899X