Effect of Hydrostatic Pressure on the Phase Transitions in {N (CH_3)_4}_2MnCl_4

概要

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The pressure-temperature phase diagram of tetramethylammonium tetra-chloromanganate {N(CH.).}.MnCl. was determined by dielectric measurements.As rressure increases the normal r>hase (I) to incommensurate rhase (II) transi-Lion temperature (19.7'C at 0 MPa) increases. The region of commensurate phasewith c=2co (TIN) becomes narrower with increasins pressure and disarrears atabout 125 MPa. A peak of dielectric constant along the a-direction is observed in apressure range from 135 MPa to 240 MPa in the incommensurate II phase. Thepeak value decreases with increasing pressure. Above about 275 MPa the normalphase I directly transforms to the lowest temperature phase V (stable below-101'C on cooling at 0MPa). The compound {N(CH.).}.MnCl. does notshow ferroelectricity at high pressure unlike to the compounds of {N(CH.).}.-ZnC1., {N(CH.).}.CoC1., and {N(CH.).}.FeCl..
社団法人日本物理学会の論文
1984-02-15