Photo-induced magnetic behavior in the amorphous spin-glass material Co 3 (SbTe 3 ) 2
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Jinke Tang Department of Physics, University of New Orleans, New Orleans, Louisiana 70148 Jin-Seung Jung Department of Chemistry, Kangnung National University, Kangnung 210-702, Korea
Jacques Ferre and Jean-Pierre Jamet Laboratoire de Physique des Solides, Batiment 510, Universite Paris-sud, 91405 Orsay, France (Received 12 April 1993; accepted 20 December 1993)
A new ternary material Co3(SbTe3)2 was prepared by using a rapid precipitation metathesis reaction between the Zintl material K3SbTe3 and CoCl2 in aqueous solution. The dc specific resistivity of this material is in the region for metallic conductors (p = 2.75 X 10" 3 fl-cm). The dc magnetic susceptibility of Co3(SbTe3)2 is reported over a 2.2 K-300 K temperature region, and the material is characterized as a spin glass with a freezing temperature of about 5 K. Magnetization data are also reported as both thermal remanent magnetization and isothermal remanent magnetization as a function of magnetizing field and temperature. When cooled well below the glass freezing temperature, the frozen spin glass has been observed to exhibit photomagnetic effects consistent with a disruption of the spin-glass state caused by uv-radiation.
I. INTRODUCTION Recent reports from our laboratory have described the synthesis and characterization of a series of ternary intermetallic chalcogenide compounds.1 These ternary metal chalcogens are prepared from a simple metathesis reaction between a Zintl phase material and a divalent transition metal halide. Because of the rapid precipitation of the intermetallic product, the materials have an amorphous structure. The physical properties of the amorphous materials are often vastly different from those of their crystalline counterparts. These new materials exhibit some remarkable properties, including specific resistivity ranging from 104 to 10~ 4 (ohm-cm), spin glass "transitions" at temperatures ranging from 4 to 30 K, and amorphous structure down to the 20 A level. Although most amorphous solids are prepared by rapid thermal quenching, pyrolytic, or sputtering techniques, chemical methods involving rapid precipitation also produce noncrystalline solids in certain types of materials.2 We have recently synthesized a new ternary Zintl compound, K3SbTe3, from a direct combination of the elements.3 The Zintl phase can be described as a polar metallic solid in which the bonding gives rise to a substantial amount of ionic character. This ionic character may be sufficient to allow the solvation of salt-like ions in some polar solvents (DMSO, DMF, formamide, ethylenediamine, and H 2 O) as shown in Reaction (1). K 3 SbTe 3 (s)
l
3K +
SbTej"
(1)
J. Mater. Res., Vol. 9, No. 4, Apr 1994 http://journals.cambridge.org
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The Zintl ion (SbTe 3 ) is quite reactive and the Zintl solution allows subsequent metathesis reaction with transition metal salts to produce amorphous intermetallic materials due to the transfer of electrons from the SbTe 3 " anion to the metal cation according to Reaction (2). 3M 2+
-
' M 3 (SbTe
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