Distribution of Metal Ions and Magnetic Properties in Spinel System CdCr2−xGaxSe4

✍ Scribed by I. Okońska-Kozłowska; E. Malicka; A. Waśkowska; J. Heimann; T. Mydlarz

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 345 KB
• Volume: 158
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2000.9053

✦ Synopsis

Single crystals of the Cd[Cr 2 ]Se 4 spinel with Ga admixtures were grown by chemical transport with an aim to study the in6uence of gallium concentration on the cation distribution and magnetic properties of the Cd+Cr+Ga+Se system. X-ray crystal structure determination showed that, unlike the system Zn+ Ga+Cr 2 Se 4 in which gallium could accommodate both tetrahedral and octahedral sites, in the compounds under study the Ga 3 ؉ ions were exclusively substituted for the magnetic Cr 3 ؉ ions on octahedral sites, while Cd 2 ؉ ions were located on tetrahedral sites of the cubic close-packed sublattice formed by the selenium ions. The chemical composition of these compounds can be written as Cd[Cr 2 ؊ x Ga x ]Se 4 (x ‫؍‬ 0, 0.02, 0.04, 0.06, 0.13). Compared to the parent CdCr 2 Se 4 , such a distribution of the cations led to considerably lowered magnetization in saturation states. The ferromagnetic Curie temperature T C was found to decrease from 129 to 120.2 K, as x varied from 0 to 0.06. The high concentration of Ga 3 ؉ (x ‫؍‬ 0.13) caused the paramagnetic Curie+Weiss temperature C+W to change the sign to a negative. The nature of the magnetic interactions, developing below T N ‫؍‬ 214 K, appeared to be altered from the ferro-to-antiferromagnetic ordering. Thus, this type of doping strongly limits the extent of ferromagnetizm in the system Cd+Cr+Ga+Se.