UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2009 Meeting


Section: Atomic and Molecular Physics; Astrophysics


Title:
EPR Evidence of Magnetic Impurities in "Gypsum Desert Rose"


Authors:
R. Slave, V. Grecu, M. N. Grecu


Affiliation:
Physics Faculty, University of Bucharest


E-mail
vvgrecu@gmail.com


Keywords:
EPR, magnetic impurities, desert rose


Abstract:
EPR Evidence of Magnetic Impurities in “Gypsum Desert Rose” R. Slave1,*), V. V. Grecu1), M. N. Grecu2) 1)Physics Faculty, University of Bucharest, 2) National Institute for Materials Physics, Bucharest Desert (sand) rose is the name given to rosette formation of gypsum or baritine with sand inclusions formed in arid conditions by sedimentation and evaporation. They are found in many dry places, Tunisia, Morocco, Arizona, Mexico, Spain, having various colors and sizes. The present investigations have been carried out on samples from Tunisia. Gypsum is not a common matrix for paramagnetic ions. Some paramagnetic centers have been identified in natural gypsum crystals subjected to irradiation with ionizing radiation [1,2]. Compared with other materials, quartz, carbonates, it is not a very good material for paleo-dosimetry determinations. Thus by itself gypsum is nonmagnetic. The samples have been cleaved from a petal of an yellowish desert rose. The petals are crystals flattened along the c axis, and the perfect cleavage plane is the [010] plane. EPR measurements were done in X-band on a JES-3X JEOL spectrometer. A quite large resonance line was determined, most probably due to magnetic inclusions in the sample. Quite surprisingly its g-factor and line width are anisotropic, depending on the angle between magnetic field and the normal on the cleavage plane. Angular and temperature dependences are reported. The data are consistent with magnetic inclusions oriented in the cleavage planes. Mean magnetization are determined and comments on shape distributions are made. [1] S. Ikeda, M. Ikeya, Appl. Rad. And Isotopes, 44, 321, 1993. [2] U. Ulusoy, Quaternary Science Rev., 23, 181, 2004.