期刊
JOURNAL OF PHYSICS-CONDENSED MATTER
卷 24, 期 4, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0953-8984/24/4/046003
关键词
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资金
- National Science Foundation through a Materials World Network [DMR 0909180]
- Schlumberger Foundation Faculty
- Materials Research Laboratory
- NSF [DMR 1121053]
- Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-AC02-06CH11357]
We examine the evolution of magnetic properties in the normal spinel oxides Mg1-xCuxCr2O4 using magnetization and heat capacity measurements. The end-member compounds of the solid solution series have been studied in some detail because of their very interesting magnetic behavior. MgCr2O4 is a highly frustrated system that undergoes a first-order structural transition at its antiferromagnetic ordering temperature. CuCr2O4 is tetragonal at room temperature as a result of Jahn-Teller active tetrahedral Cu2+ and undergoes a magnetic transition at 135 K. Substitution of magnetic cations for diamagnetic Mg2+ on the tetrahedral A site in the compositional series Mg1-xCuxCr2O4 dramatically affects magnetic behavior. In the composition range 0 <= x <= approximate to 0.3, the compounds are antiferromagnetic. A sharp peak observed at 12.5 K in the heat capacity of MgCr2O4 corresponding to a magnetically driven first-order structural transition is suppressed even for small x. Uncompensated magnetism-with open magnetization loops-develops for samples in the x range approximate to 0.43 <= x <= 1. Multiple magnetic ordering temperatures and large coercive fields emerge in the intermediate composition range 0 : 43 <= x <= 0.47. The Neel temperature increases with increasing x across the series while the value of the Curie-Weiss (CW)-C-Theta decreases. A magnetic temperature-composition phase diagram of the solid solution series is presented.
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