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Temperature dependence of the dielectric constant of würster's blue perchlorate around the transition temperature
Vdnne
32,‘numk&
3
CHEkHXL
PHYSICS LETTERS
.,
1 May 1975
.’ ‘.
: ‘.- TiMPERiTURE ,.OF.wiiRsTERk
DEPENQENCE
OF THE BPEEECTRIC &NSTkVT
BLUE PERCHLORATE ,.
AROUND ..
*iHE WSITlON
TEMPERA=
Kikujiro I?3II Insfitife far Solid State Physics, Univmi~,of
T&o,
Roppngi,
Tookyo.Iapun
and Harug KIRODA’
..
Department of Chemhy,
Faculty ofscience, Chiversity of Tokyo, Hongo. Tokyo. Japm
Received27 Jahary 1975
A tekperature-dependent dieiectic behavior is obsei-ved on Wkster’s blue perchlonte (T&SD’. Cl02 are-xnd iis phase transition temperature. Soft modes of the lattice viiration are suggested to be the cause of this Zelectic constant anomaly.
N,N,N’,N’-tetramethyl-p-phenylenediaminium
-m abrupt change in the intensity of the charge-transfer band is observed around the transition temperature, which also exhibits a good correlation with the variation in the paramagnetism [lo], In the case of K+CA-, we have found that the dielectric constant increases in pa&e1 with the intensity increase of the charge-transfer band, and we therefore considered that the temperature dependence TMPD+ ions,‘and its intensity markedly increases of the dielectric consttit in the vicinity of the transition point is dominated by the chauge in the electrbelow the transition temperature showing a good COTrelation with +he decrease of the pammagnetism [4]. nit polarivbility term -o&ted with the low-%ergy , Recently, the crystal structures of both the high. charge-transfer transition [l l,f2]. ‘and low-temperature phases were reported [5,6]. The On tha other ha.nd,‘we found a quite different temconspicuous difference between them is to be found .’ perature de$nd&ce of the dielectric constant in the in the way TMPbf ions are stacked; I-h&+ ions case of WBP. In the. present paper we will report this form a’mondmeric linear chain in the high-temperature ., novel dielectric behavior of WP around its transition phase, but take on a dime& arra:lin the low-temperteinperature, &d discuss its possible cause. WBP was obtked by the method of Michaelis and ature phase, in which TMPD” ions close up alternately with small side steps. The mqnetic +d op+l be- . Chard [13] as a fine~crystallinepowder. Its dielechavior reported earlier can be well understood on the tric constant was measured on the. powder sample by basis of this structural difference by the use ‘of a paremploying cavi@-pxturbation-method at 9.4 GHz [12]. Tlii. saniple was packed in a thin fused-quartz ticular model of the antiferromagnetic interaction [7] : between TMJ?D+ ions. tube w&h was evacuated to ,below 10W3 t&r. The temperature of the sample was controlled by introhs regards.the,magnetic and optical properties, the phase transition of WE3Phas similarities in severa! ducing liquid nitrogen or cold nitrogen gas around the iespects ti*th those of K+(TCNQand K+. (~hlomil) resonant ~~ii~j, : [8,9]. In the case of ~(c~oranil)(hereafter written ‘. .., 607 ,,“.’ . . ,’ ‘.I ,. ,. -. : ., ,‘,. -,
(TMPD’) perchlorate (Wiirster’sblue pzrchlorate, WIjP) is knoWn as one of the typical examples of a. radical salt. It undergoes an antiferromagnetic-paramagnetic transition in the vicinity of 190 K [1,2], a specific heat peak being observed at 189.9 K [3]. It vm reported that this salt exhibits a near-infrared absorption band Associated with charge transfer between
as @CA-),
infrared charge-tram-.
” ,.
.,.
300 Tempfiature
..
tant, decreases below : the transiti& temperature whereas the intensity of the charge transfer band ~on~u~usly.~~reases [4]. In this respe,ct, the dielectric behavior of WBP is distinctly diffitrent from that of K+CA-, so‘that it C&Inot be. ~~d~rsto~d in terms of the mod& which we .- 1 have assumed for the, interpretation of.the latter [12]. In the temperature dependence of the dielectric,
,’
(%)
.Fig.f. Temperature de~~~d~~~ of tk Wiiskk’s biue,y;skhiorate. C$ -,$)/j$
of
~elec~~‘cons~t
is plotted
as the
-ordinate, Ghere fi and fi iwe the resonm.c=e frequcncils
of
the .micro~ve cavity Mithand without the sample, respec‘tiV$y. An approbate scale Gftke ~&eiectriccbnstant is : shown in the right hand side, :.
:
._
:.
with and without
above,
w& should
note
tw&
and the other is the gadualchanges above and below this temperature. A similar temperature tion point,
The’.clielkcfric constant * of V@P at room’~emperbe.43 by the procedures ‘. desciibed previously 1141. kfig. 1, we have plotted’. (FT .:f$/fg against temperature, where fl and& are frequencies
of‘ WBP descr&ed
features; the' firstis the sudden decrease at the, tknsi-
..
at&! was detkinedto
the resonke
constant
..
the sam-
ple, respectively. Since V: -@/j-z
is proportional, [14];the above plot can be taken as one which shows the varia: tion of dielectrk constant, the approximate scaIe of’ dielectric constant bking given on t&right hand “.&jet*, :. As is seek in fig. I, the dielectric Constant is almost independent of temperature at 250-300 Kj but ~a‘.dklly ~cr~~s~s as the te~p~r~tu~e is lowered to the to s..i l’.m the first order aPpro~~ation
transSt.ioripoint. It shows a maximum at the t&ition point, then suddenly decreases; The maximum : corresponds to ihe. ~eIect~c,~onsta~t’4.7, which is ,!argr by abput 6% than .the robm temperature value.
-..
dependen’= is known to OCCUI~ in a crystal containing -, a component with an electric, dipole which is able to rotate in the high-temperature phas,e. However, such a model carinot be applied for the case of WBP. Recenti+, Te;auchi [ 151 observed a diffuse X-ray
reflection aiising from the fluctuating dimerization of TMPD+ ions above the tr~sition temperature. As the ” temperature is lowered, the intensity of this Gfle$ tion increzcies proportionally to l/(T-T,) where T, ‘. is’a crhical temperature close to the transition point. ’ This behatior suggests th&a phonon mode along the ‘4 a$s 6f the crystal is softened in the vicinity of the transition point. The fluctuation of fi; the angle be-
twien the ofand c axes fs also found to be stimulated the samktemperaj~e range. It is, therefore, plausible that mine optical modes of the lattice vibration with wave *fector k = O’are soften& in this temperature in
r?kge,.so that the lattice polarizabihty isanomalously’ increased. I:f this is the case, the dielectric behavirjr i dbserved here& the v+iriity of the tram&on tern- ‘, perature cnuld be regarded as arising from the ioft,en.ingofthzphononmpdes. ; ” ,. ‘. dielectric cmistants of the crystal. ‘, Pott and Komm&rdcur f16) first reported&e ob- 11: **. ?O obtain tlxi temperature depenc&x& of the dielectric : c&ant the volume needs to-be corrected by u&g&e ,‘. r&vation:of an anomaIo& current peak,at the k&ithen& expkion coefficient. However,it dan be shokn .: tion te’mperatue d,uri.ngth! measurement of the electhat, the mc&ed valuk of & -&I/i; will npt be ’ ‘. tricaJ condactidy of WBP.,We &so.notiSed that a ; Sfected by the? timpIe volume iri the Erst ~pp~oxiination. similar ph~~~m~non often $&es’place in the dc conllqefo!e, we ,u~ directly, I&& the +ser~ed frequency ‘. ‘ductivity-+eeuremen& tinWl3P crystak Possibly,, . change to the dielectric.conStantef the sampk without
As the temperature is lowered further, the diektric’ .. : _:’ .: . . . .. * The value given isthe mean valukof the arkotropic
cmre+ng fir the G&ion of volume. _, ?.hk trti$ent c~ti@ 6. ihe dne that-a&3 .. ;.. ., .,‘. .: :. ,,: ,, .‘(.‘, .. . . :-‘. ‘_ . ..i __ .‘608 .,”,. ‘..Y.._:- :. 1‘ 1. ,,,, ;: ., .:y y.1 ‘, ;.I ,I. ;_‘:y .;, .,_ .: ~‘~,.,~,.~,~~~,~,,~~ .,.:.._.,;.’ _.,:; ,.,I :-.. /,’ ” ,,. .:: . ..j., ‘. ,, :.: ,, .’.,‘., ;,,:..,,.,:; ,.. : :. ,‘. ._ .;’ :.:.:. ‘. .’‘; ..,. ,.’ .- __._.’ “’ ,., :.; ,,/” .._ :.:.A_ .,. .;_ I’ _” :. ,:‘ .; ,_. ., .- ,,., ‘. :.:--
from the : .;.. ‘: ,:’ ., :.;.’ _.,.
Volume 32,number
3
CI-IEMICAL PHYSICSLETTERS
streep increase of the.electrical dapacitance of the sample caused by the sudden change of dielectric ‘constant accompanying the phase transition. ‘The authors wish to thank Dr. Terauchi.for the information on his unpublished results of the X-ray diffraction. -
Fteferences [l] W. Duffy, J. Chen Phys. 36 (1962) 490. [2] IL Okumura, I. Phys Sot. Japan 18 (1963) 69. [3] JX -a, M Nrikanua and S. S&i. Bull Chcm Sot Japan 38 (1965) 1776. [4] T. Sakata and S. Nagkura, Bull. Chem. Sot Japan 42 (1969) 1497. [5] J.L. de Boer and A. Vos, Acta Cryst. B28 (1972) 835.
Z May i975
[6] J.L. de Boer and k Vos, Acth Cryst B38 (1972) 839.
[7] D.D. Thomas, I-L KeUer and ttbf. bCcConnell, J. Chem Phys. 39 (1963) 2321. [a] LG. Vegter, T. Hibnia and J. Kommuldeur, Chem Phyr letters 3 (1969) 427. [9] J.J. Andri and G. Weill, Chem Phys. Letters 9 (1971) 27. [ 10) S. Hiroma and H. Kuoda, Bu’L Chem Sot Japan 46 (1973) 3645. [l I] K. Ishti, M_ Kinoshita and FL Kuroda, in: Engeera and charge transfer in orguic semiconductors, eds. K. Mosuda and M. Silver (Plenum Press, New York, 1973) p. 183. [12] K. Ishii and H. Kuroda, to be published, [ 131 L hfichaelis and S. Graruck, I. Am. Chem. Sot 65 (1943) 1747. [ 141 K. Ishii, M. Kinoshih and H. Kuroda, &ILL CherrL SOL Japan 46 (1973) 3385. [15] A. Terauchi, private‘communication. [16] G.T. Pott and J. Kommandeur, 5. Chem Phys. 47 (1967) 395.
32,‘numk&
3
CHEkHXL
PHYSICS LETTERS
.,
1 May 1975
.’ ‘.
: ‘.- TiMPERiTURE ,.OF.wiiRsTERk
DEPENQENCE
OF THE BPEEECTRIC &NSTkVT
BLUE PERCHLORATE ,.
AROUND ..
*iHE WSITlON
TEMPERA=
Kikujiro I?3II Insfitife far Solid State Physics, Univmi~,of
T&o,
Roppngi,
Tookyo.Iapun
and Harug KIRODA’
..
Department of Chemhy,
Faculty ofscience, Chiversity of Tokyo, Hongo. Tokyo. Japm
Received27 Jahary 1975
A tekperature-dependent dieiectic behavior is obsei-ved on Wkster’s blue perchlonte (T&SD’. Cl02 are-xnd iis phase transition temperature. Soft modes of the lattice viiration are suggested to be the cause of this Zelectic constant anomaly.
N,N,N’,N’-tetramethyl-p-phenylenediaminium
-m abrupt change in the intensity of the charge-transfer band is observed around the transition temperature, which also exhibits a good correlation with the variation in the paramagnetism [lo], In the case of K+CA-, we have found that the dielectric constant increases in pa&e1 with the intensity increase of the charge-transfer band, and we therefore considered that the temperature dependence TMPD+ ions,‘and its intensity markedly increases of the dielectric consttit in the vicinity of the transition point is dominated by the chauge in the electrbelow the transition temperature showing a good COTrelation with +he decrease of the pammagnetism [4]. nit polarivbility term -o&ted with the low-%ergy , Recently, the crystal structures of both the high. charge-transfer transition [l l,f2]. ‘and low-temperature phases were reported [5,6]. The On tha other ha.nd,‘we found a quite different temconspicuous difference between them is to be found .’ perature de$nd&ce of the dielectric constant in the in the way TMPbf ions are stacked; I-h&+ ions case of WBP. In the. present paper we will report this form a’mondmeric linear chain in the high-temperature ., novel dielectric behavior of WP around its transition phase, but take on a dime& arra:lin the low-temperteinperature, &d discuss its possible cause. WBP was obtked by the method of Michaelis and ature phase, in which TMPD” ions close up alternately with small side steps. The mqnetic +d op+l be- . Chard [13] as a fine~crystallinepowder. Its dielechavior reported earlier can be well understood on the tric constant was measured on the. powder sample by basis of this structural difference by the use ‘of a paremploying cavi@-pxturbation-method at 9.4 GHz [12]. Tlii. saniple was packed in a thin fused-quartz ticular model of the antiferromagnetic interaction [7] : between TMJ?D+ ions. tube w&h was evacuated to ,below 10W3 t&r. The temperature of the sample was controlled by introhs regards.the,magnetic and optical properties, the phase transition of WE3Phas similarities in severa! ducing liquid nitrogen or cold nitrogen gas around the iespects ti*th those of K+(TCNQand K+. (~hlomil) resonant ~~ii~j, : [8,9]. In the case of ~(c~oranil)(hereafter written ‘. .., 607 ,,“.’ . . ,’ ‘.I ,. ,. -. : ., ,‘,. -,
(TMPD’) perchlorate (Wiirster’sblue pzrchlorate, WIjP) is knoWn as one of the typical examples of a. radical salt. It undergoes an antiferromagnetic-paramagnetic transition in the vicinity of 190 K [1,2], a specific heat peak being observed at 189.9 K [3]. It vm reported that this salt exhibits a near-infrared absorption band Associated with charge transfer between
as @CA-),
infrared charge-tram-.
” ,.
.,.
300 Tempfiature
..
tant, decreases below : the transiti& temperature whereas the intensity of the charge transfer band ~on~u~usly.~~reases [4]. In this respe,ct, the dielectric behavior of WBP is distinctly diffitrent from that of K+CA-, so‘that it C&Inot be. ~~d~rsto~d in terms of the mod& which we .- 1 have assumed for the, interpretation of.the latter [12]. In the temperature dependence of the dielectric,
,’
(%)
.Fig.f. Temperature de~~~d~~~ of tk Wiiskk’s biue,y;skhiorate. C$ -,$)/j$
of
~elec~~‘cons~t
is plotted
as the
-ordinate, Ghere fi and fi iwe the resonm.c=e frequcncils
of
the .micro~ve cavity Mithand without the sample, respec‘tiV$y. An approbate scale Gftke ~&eiectriccbnstant is : shown in the right hand side, :.
:
._
:.
with and without
above,
w& should
note
tw&
and the other is the gadualchanges above and below this temperature. A similar temperature tion point,
The’.clielkcfric constant * of V@P at room’~emperbe.43 by the procedures ‘. desciibed previously 1141. kfig. 1, we have plotted’. (FT .:f$/fg against temperature, where fl and& are frequencies
of‘ WBP descr&ed
features; the' firstis the sudden decrease at the, tknsi-
..
at&! was detkinedto
the resonke
constant
..
the sam-
ple, respectively. Since V: -@/j-z
is proportional, [14];the above plot can be taken as one which shows the varia: tion of dielectrk constant, the approximate scaIe of’ dielectric constant bking given on t&right hand “.&jet*, :. As is seek in fig. I, the dielectric Constant is almost independent of temperature at 250-300 Kj but ~a‘.dklly ~cr~~s~s as the te~p~r~tu~e is lowered to the to s..i l’.m the first order aPpro~~ation
transSt.ioripoint. It shows a maximum at the t&ition point, then suddenly decreases; The maximum : corresponds to ihe. ~eIect~c,~onsta~t’4.7, which is ,!argr by abput 6% than .the robm temperature value.
-..
dependen’= is known to OCCUI~ in a crystal containing -, a component with an electric, dipole which is able to rotate in the high-temperature phas,e. However, such a model carinot be applied for the case of WBP. Recenti+, Te;auchi [ 151 observed a diffuse X-ray
reflection aiising from the fluctuating dimerization of TMPD+ ions above the tr~sition temperature. As the ” temperature is lowered, the intensity of this Gfle$ tion increzcies proportionally to l/(T-T,) where T, ‘. is’a crhical temperature close to the transition point. ’ This behatior suggests th&a phonon mode along the ‘4 a$s 6f the crystal is softened in the vicinity of the transition point. The fluctuation of fi; the angle be-
twien the ofand c axes fs also found to be stimulated the samktemperaj~e range. It is, therefore, plausible that mine optical modes of the lattice vibration with wave *fector k = O’are soften& in this temperature in
r?kge,.so that the lattice polarizabihty isanomalously’ increased. I:f this is the case, the dielectric behavirjr i dbserved here& the v+iriity of the tram&on tern- ‘, perature cnuld be regarded as arising from the ioft,en.ingofthzphononmpdes. ; ” ,. ‘. dielectric cmistants of the crystal. ‘, Pott and Komm&rdcur f16) first reported&e ob- 11: **. ?O obtain tlxi temperature depenc&x& of the dielectric : c&ant the volume needs to-be corrected by u&g&e ,‘. r&vation:of an anomaIo& current peak,at the k&ithen& expkion coefficient. However,it dan be shokn .: tion te’mperatue d,uri.ngth! measurement of the electhat, the mc&ed valuk of & -&I/i; will npt be ’ ‘. tricaJ condactidy of WBP.,We &so.notiSed that a ; Sfected by the? timpIe volume iri the Erst ~pp~oxiination. similar ph~~~m~non often $&es’place in the dc conllqefo!e, we ,u~ directly, I&& the +ser~ed frequency ‘. ‘ductivity-+eeuremen& tinWl3P crystak Possibly,, . change to the dielectric.conStantef the sampk without
As the temperature is lowered further, the diektric’ .. : _:’ .: . . . .. * The value given isthe mean valukof the arkotropic
cmre+ng fir the G&ion of volume. _, ?.hk trti$ent c~ti@ 6. ihe dne that-a&3 .. ;.. ., .,‘. .: :. ,,: ,, .‘(.‘, .. . . :-‘. ‘_ . ..i __ .‘608 .,”,. ‘..Y.._:- :. 1‘ 1. ,,,, ;: ., .:y y.1 ‘, ;.I ,I. ;_‘:y .;, .,_ .: ~‘~,.,~,.~,~~~,~,,~~ .,.:.._.,;.’ _.,:; ,.,I :-.. /,’ ” ,,. .:: . ..j., ‘. ,, :.: ,, .’.,‘., ;,,:..,,.,:; ,.. : :. ,‘. ._ .;’ :.:.:. ‘. .’‘; ..,. ,.’ .- __._.’ “’ ,., :.; ,,/” .._ :.:.A_ .,. .;_ I’ _” :. ,:‘ .; ,_. ., .- ,,., ‘. :.:--
from the : .;.. ‘: ,:’ ., :.;.’ _.,.
Volume 32,number
3
CI-IEMICAL PHYSICSLETTERS
streep increase of the.electrical dapacitance of the sample caused by the sudden change of dielectric ‘constant accompanying the phase transition. ‘The authors wish to thank Dr. Terauchi.for the information on his unpublished results of the X-ray diffraction. -
Fteferences [l] W. Duffy, J. Chen Phys. 36 (1962) 490. [2] IL Okumura, I. Phys Sot. Japan 18 (1963) 69. [3] JX -a, M Nrikanua and S. S&i. Bull Chcm Sot Japan 38 (1965) 1776. [4] T. Sakata and S. Nagkura, Bull. Chem. Sot Japan 42 (1969) 1497. [5] J.L. de Boer and A. Vos, Acta Cryst. B28 (1972) 835.
Z May i975
[6] J.L. de Boer and k Vos, Acth Cryst B38 (1972) 839.
[7] D.D. Thomas, I-L KeUer and ttbf. bCcConnell, J. Chem Phys. 39 (1963) 2321. [a] LG. Vegter, T. Hibnia and J. Kommuldeur, Chem Phyr letters 3 (1969) 427. [9] J.J. Andri and G. Weill, Chem Phys. Letters 9 (1971) 27. [ 10) S. Hiroma and H. Kuoda, Bu’L Chem Sot Japan 46 (1973) 3645. [l I] K. Ishti, M_ Kinoshita and FL Kuroda, in: Engeera and charge transfer in orguic semiconductors, eds. K. Mosuda and M. Silver (Plenum Press, New York, 1973) p. 183. [12] K. Ishii and H. Kuroda, to be published, [ 131 L hfichaelis and S. Graruck, I. Am. Chem. Sot 65 (1943) 1747. [ 141 K. Ishii, M. Kinoshih and H. Kuroda, &ILL CherrL SOL Japan 46 (1973) 3385. [15] A. Terauchi, private‘communication. [16] G.T. Pott and J. Kommandeur, 5. Chem Phys. 47 (1967) 395.