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Pressure Dependence of Ferromagnetic Phase Transitions of Chromium Chalcogenide Spinels

 

作者: Vishnu C. Srivastava,  

 

期刊: Journal of Applied Physics  (AIP Available online 1969)
卷期: Volume 40, issue 3  

页码: 1017-1019

 

ISSN:0021-8979

 

年代: 1969

 

DOI:10.1063/1.1657510

 

出版商: AIP

 

数据来源: AIP

 

摘要:

The shift in the Curie temperatureTchas been measured as a function of hydrostatic pressure up to 10 kbars for the chromium chalcogenide spinels CdCr2Se4, HgCr2Se4, CdCr2S4, and HgCr2S4, by measuring the mutual inductance of an astatic coil assembly containing the sample. Also the compressibility of these compounds has been measured for the same pressure range at three temperatures. The measured values ofTcanddTc/dPfor CdCr2Se4, HgCr2Se4, CdCr2S4, and HgCr2S4are 128°, 105.5°, 84°, and 36.1°K and −0.82, −0.95, −0.58, and +0.14°K/Kbar, respectively. Combining the compressibility measurements withdTc/dPthe values ofdTc/da=+66, +99, +46, and −10°K/Å are obtained for CdCr2Se4, HgCr2Se4, CdCr2S4, HgCr2S4, respectively. These values ofdTc/dafor CdCr2Se4and CdCr2S4are in qualitative agreement with the dilution studies for these compounds. However, the value ofdTc/dafor HgCr2S4is of opposite sign from that predicted from the solid‐solution studies for this compound. High‐pressure measurements seem to provide a better picture of variation of magnetic exchange interaction than dilution studies, because for the latter, the covalency effects become different due to changes in the nature of atomic environments. Conclusions are also made about the volume dependence of exchange interactions in these materials, and again it is quite different for HgCr2S4as compared to the volume dependence of exchange interactions for the other three compounds. This seems to be consistent with the recent experimental and theoretical studies for HgCr2S4.

 

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