Negative chemical pressure effects induced by Y substitution for Ca on the ‘exotic’ magnetic behavior of the spin-chain compound, Ca3Co2O6 |
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Authors: | S Rayaprol E V Sampathkumaran |
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Institution: | (1) Department of Condensed Matter Physics and Material Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, 400 005 Mumbai, India |
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Abstract: | The magnetic behavior of a solid solution, Ca3 x Yx CO2 O6, based on the ‘exotic’ spin-chain compound, Ca3Co2O6, crystallizing in K4CdCl6-derived rhombohedral structure is investigated. Among the compositions investigated(x = 0.0, 0.3, 0.5, 0.75 and 1.0), single-phase formation persists up tox = 0.75, with the elongation of the c-axis. The present investigations reveal that the temperature at which the ‘so-called’
‘partially disordered antiferromagnetic structure’ sets in (which occurs at 24 K for the parent compound,x = 0.0) undergoes gradual reduction with the substitution of Y for Ca, attaining the value of about 2.2 K for the nominalx = 1.0. The trend observed in this characteristic temperature is opposite to that reported under external pressure, thereby
establishing that Y substitution exerts negative chemical pressure. Anomalous steps observed in the isothermal magnetization
at very low temperatures (around 2 K) forx = 0.0, which have been proposed to arise from ‘quantum tunneling effects’ are found to vanish by a small substitution (x = 0.3) of Y for Ca. Systematics in AC and DC magnetic susceptibility behavior with Y substitution for Ca have also been probed.
We believe that the present results involving the expansion of chain length without disrupting the magnetic chain may be useful
to the overall understanding of the novel magnetism of the parent compound. |
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Keywords: | Spin-chains Ca3Co2O6 chemical pressure magnetic order quantum tunneling |
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