Page 1
Title <研究ノート>正方格子量子スピン系で実現した113磁化プラトー
Author(s) 辻本, 吉廣; 陰山, 洋; 網代, 芳民; 吉村, 一良
Citation 低温物質科学研究センター誌 : LTMセンター誌 (2008),12: 12-20
Issue Date 2008-06-01
URL https://doi.org/10.14989/153219
Right
Type Departmental Bulletin Paper
Textversion publisher
Kyoto University
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DEF+*+678)GHIJK1/3LMNO<-
Realization of the 1/3 Magnetization Plateau in Square-Lattice Quantum Spin systems
PQRSTUVWTXYZ[TR\] ̂ÁÂÃ�Ã�ù ñ���� M�¸û
Yoshihiro Tsujimoto, Hiroshi Kageyama, Yoshitami Ajiro, Kazuyoshi Yoshimura Department of Chemistry, Graduate School of Science, Kyoto University
A new triple-layered perovskite (CuBr)Sr2Nb3O10 with the S = 1/2 square lattice, has been prepared by the topotactic ion-exchange reactions. Specific heat measurements in zero fields revealed two anomalies at low temperatures, suggesting the presence of successive phase transitions due to the competing ferro- and antiferromagnetic interactions in the layer. When the magnetic field is switched on, a novel phase appears which is characterized by a 1/3-plateau of the full magnetization, which has only been theoretically expected for triangular-based lattices.
"
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AB CDEF&
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Óê DEF+(J1>J2QR.)à
Page 3
! 2. n = 3)(g@ÌL6ó[<��AFA2B3O10
(AF = Rb, Cs;A = La, Ca, Sr; B = Ti, Nb, Ta; X = Cl,Br)Î
ÄnÄJK[õ8�Gyøb�àCuX2Äbyø1
¡AF'Ä(CuX)'Ó�GJÉ(CuX)A2B3O10Ó³úd4à
õöJØ`1"GÅA1@"?bãÓÃãbÍÐ1Å*Ô�òLO6<ª-}�8Å�ᡳØ`bG
ßÏÙÏÐ !1(b)1pJK�1@"�0^H�6�$J1 > 0%ö3JÏêÏØ`ÍÐ@"4éýb678Î
�ÉyÈÌð1ìFK_`ÓtuGß¡LO6<ª-}�8Å[ëØ`1"JÏJ@"È�6-b67
8s1H�6�$J2>0%b¨6Î��Ø�#G64áÄ :ÉDEF+-1LO6<ª-}�8Îq
�÷4áÄÓGð45!1(c)61"HÎ@Nb ÙØ��ÄJÉ@ J2M8ðÎ25%bBCìGÎDò1q�
JKSrCu2(BO3)2$Shastry-SutherlandF+%[2] ÓÍúdÉ`41 100%bBCì1Èø÷4J1#J2QR.
Å1�opqb��b¬EÏúl¿1_�ØQR.Gß4ÓTñ���Óÿ¢JÉ`4bÓIgGß
¡T0&1Ø:É Ù� ZnVO(PO4)"ÄNb¬E��Ó��ÖdKbcGß4[3]à "
"
tBuvR%w$%xyz{|&
" ��Ð77Å|¿b1�)HyøGųú
dØ`��Î64áÄÓGð4F§òØ'7
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§�BâH1Èúd4b1ÈJ@"q²ÅG�
�1"_Öd4K�H!1HúdØ`èBâ
HÓ³úd4ÏúGß41"��Ð7bØÏG
;Ú1<Z�n~bmnyøÄabd4ÍÐ
1ÅTÄnÎIµ1�`4K�@"Änb«�1
øëÉJ:K'(ÎÐñò1),÷4áÄÓ
Gð41"±��öGÅ[õ8�Gyø1 :
ÉÐ7Öd4Dion-Jacobsonµ(g@ÌL6ó
[<KM�(CuX)An>1BnO3n+1 (n = @ÌL6ó[
<LÌmnb(ã; X = Cl>, Br>; A = La3+, Ca2+,
Sr2+; B = Nb5+, Ta5+)1ª!J@"Nb����Î
¢Ø:É`41"!21n = 3b[õ8�Gyø1
234'(úMb�+Îp÷1"ÄnA’A2B3O10
b@ÌL6ó[<LÌmn1MVdKA’+[õ
8bN[<1@[õ8�G1 :ÉJÌ;8GOPÖdKCu2' (S = 1/2)b:#ÆDEF+(CuX)'GÓq
�Öd41"CuÅé]Ç�1ß4QÝëJKJÌ;8bR1@"-§b$BO6b%Kä1 :ÉSVdÉ
`41"ááGL�bÓÔÏúa5b_�ØÚT1×� 1"]5�Å@L�("(CuX)'"ÓlL�b
5A2B3O106>ÎÅÖG16 Å/�(n = 2"bÍÐÅ12 Å)ÊdÉ`4K�Táb��bL�1Å^`:#Æ
�ÄNd1�x÷4*+/0ÓId4áÄÓ��Öd4áÄGß41":5�ÅL�(b*Ô�ò_
`Gß41"CuÓd7÷4DEF+b³U1JÌ;8s+Óé`÷4K�@"?1V:K�L�ò�GH
�6�ÄÈ�EÌ1V:Ky�L�ò�GH�6�Äbs1�`�Ð@"5V¡678LO6<ª-
}�8$J1#J2QR.%Ó��Öd41"Öú1@"]¥#ÎùÉïÏ4 Ù1X, A, B N[<ÎúF4á
Ä1 :ÉL�Î)Wò1úMÖBúd4XÔ;ß41"5V¡@"Q)ÅLO6<ª-<JKDEF
+)ÓËÇJÉ`4QKÀYÄNd1�ÙñeÀYÄ`ÙZLO6<ª-}�8[ÎeuJÉ d4
��/ÄJÉ��Öd41"HÎ@"\�ÓádVG3§ò1\®ÉðK:()$n=2%"(CuX)LaNb2O7 (X
= Cl, Br) ÅÇ�by�L�Ä�L�H�6�ÓEöJKLO6<ª-}�8ÄJÉbÚTÎpJ@"
JÌ;8[õ8b]^1 :É��ÓÃð úM÷41"X = ClnÅ678lnbvwghÎ4¡Ï5
Page 4
LÍ1 :É�+K8bM-Ü9I[8}_�[8ÑÒÎ�á÷XY=`*+IÞÎ`÷4b1ÈJ"
a4b@"X = BrnÅ32KGØ-;ÂI-µby�L�ef(CAF)Îp÷"a5b1S°1EF4Ä@"a()12
`ÉÅ#Æ�bÌ-1 4*+�ú�b1V¡Ó��Gð4K�@":()ÄÅÛØ4��ÓId4
tu�Óß41"QcGÅ@"HÎ1:()ÄÅ� ÛØ4*+IÞÎpJK�ÎLO6<ª-<��
(CuBr)Sr2Nb3O10b��ÎÐ7T'(edÄÄ;1eÁ÷4"a6b1"
"
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" ÄnRbSr2Nb3O10Å|¿b1�)Hyø1 :ÉÐ7÷4áÄÓGð41"8���ÄJÉRb2CO3,
SrCO3 NJÉNb2O5bEÐ�ÎI.ô�45ç1�dù׳850f, 12 hGgh�@"1050f, 24 hG:�
miñ΢:K1"h7q1ÅRb2CO3bj�1 4kvÎÙÙK�@"M�*�Ib25%{U/l1�
`K1"h7�@myøG :KRb2CO3ÎnoÒGpqJrs÷4áÄ1 :ÉSHbRbSr2Nb3O10Î
³K1"#1@"I.>8GBtJK+Ì-LMmn6�GÄnÄCuBr2Î Ez@ªm<17dJK1"
ábÄð@"CuBr2ÎM�*�Ib:Õ�`K1"Nb�¨[ªmn6u1�dvùw�$PO2 = 10>3 Torr%
JK�@"350fG]xsh7΢Ø:K1yø�@"y[7�bRbCl2ÄmyøbCuBr2ÎnoÒGpqJ@"
(CuBr)Sr2Nb3O10 ÎSÊJK1ÄnÅlL�Gß4áÄÎyzJÉ{LGß4Ó@"|nÅCu2+[õ8b
õö1 ¡}LÄØ41"
"
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Îh�'(ÄJÉ;-<«.<ed뢯 ,̀ '(
¨Oý-�-b3üM΢Ø:K1"NbÛ0Î!31
p÷1"F+âãÅa = 3.90997(3) Å, c = 16.0197(2) Å, H
= 90�$Z = 1%Gß41"À��x+Å@"Rwp = 9.25%, Rp
= 7.16%TS = 2.42ÄËï1vôJÉ`41"JÏJ@"Br
N[<bhE�s+úé¨Oý-�-UisoÅ
0.0441(19) Å2ÄIRòÃð @"ábáÄÅBrs+Ó
Ú�é 1̀b1`4bGÅØ T ¡]¥òØN[<1
`ìò1ï¤JÉ`4áÄÎpßJÉ`41"HÎ@é
�b?Ó:()(CuX)LaNb2O7 (X = Cl, Br) [7]�"
(CuCl)Ca2Nb3O10 [8]12`É;:�ÖdÉ2¡@"
P4/mmmbùs/bVVGBrs+Ó4m (x,0,1/2) ;J
Å4k (x,x,1/2)125%b`ìGê�É`4QR.ÓÏ�ÖdÉ`41"NáGq�ÎmE1@"
(CuBr)Sr2Nb3O10bBrs+Ó4mN[<;J Å4kN[<1úéJKQR.ÎgâJÉ3üM΢Ø:
KÄáÏ@"©N[<1234úéÅx = 0.439(3), 0.457(2)ÄØ¡@"UisoÅU¡úbÍÐ12`É;
0.020(3)�Ä��JK1"JÏJØÓú@"À��x+ÅRwp = 9.15, 9.16 ÄNdæd��ÖÉ`4;bb,
U¡ú;{çéëæ1vôJÉ`4bGI�ÅGÅU¡úbQR.Ó ¡DJ`bÏÎ�â÷4á
ÄÅGðØ`à
! 3. (CuBr)Sr2Nb3O10bX6;-<«.<ed
¨�-8à�Lb}8M.(+), �LbH6, O
LbH6, �Lb�6ÅNdædHâæ, ,-
æ, Ndúb z, LOm+y�bé`Î�÷à
Page 5
lBU�������k&
" !4(a)1SQUIDLô,Î�`É0.1 TbLͧG
ââJK(CuBr)Sr2Nb3O10~�·¸bLMìIb��
ºõ�Îp÷à1�õïÎ��1ºõJØ`�Î�
FKj_;-#�[6D, I = C / (T >.G) + I0 GL
bm~b8+΢`, j_;-âã C = 0.408(1)
[emu K/mol], �[6�� . = 20.9 (3) K, I0
=G>1.36(3) 0 10>4 [emu/mol]γKàC Å1 molbCu2+
1��Öd4æ$g = 2bÄðC=0.375 [emu K.mol]%
Ä ]�JÉ`4áÄÏú, [õ8�GyøÓ
{çñ4ò1¢ØAdKÄùØB4àábÄðg =
2.176 1Ø4à�[6��ÓDGß4áÄÅ, y�
L�ò(AFM) J2 ¡�L�ò(FM) J1 bEÓ"_
òGß4áÄÎ�YJÉ2¡TËb�[6��ÎÄ
4(CuCl)LaNb2O7 (. = >9.6 K) �(CuBr)LaNb2O7 (. =
>5.1 K) ÄÅÈ�òGß4Ó�L�Äy�L�H�
6�ÓEö÷4Ä`ÙÔGÅÝ|JÉ`4à��Ó
100Kÿ§1Ø4Ä, LMìÅ�ÉÊefb��Î
yzJÉj_;-9�[6DÏúcd��4Ó�#
Æy�L�n1Úëb��ÏØ�ÃÅpÖØ`à5
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MìââbcÏúL×efÓ�ðÉ`4bÏUÙ
ÏÅ�ZGðØ .̀
" H¼2bë�Î\®4K�1Imââ΢Ø:
Kà!5Å�Lͧ1234�ImCpb��ºõ�
ÎNÌm<JK;bGß4Ó, 9.3 K (Tc1)Ä7.5 K
(Tc2)1�#H¼2Îpß÷4:5b7-nÓ�w
1ÓâÖdKà�#H¼2Å*Ô�òLO6<ª-
}�8Î;5�#Æ��1ÚëbIÞGß¡ ,
CsCoCl3�CsNiCl3ØUba�F+)GÓâÖdÉ
`4 [9]à�:É, (CuBr)Sr2Nb3O1012`É;*Ô�
LO6<ª-}�8Óáb�#H¼2IÞ1_�
Ø��Î0KJÉ`4ÄEF4bÓ��GßÏÙà
5V¡, Tc1 G¿L�ghÏúØúÏbL×ef
Î;:K³sH(M1)Î.K�, Tc2 G�ú ¡e
fMJKgh(M2)�ÄH¼2JÉ`4ÄÐâÖd
4à;JM1HÓß4«bL×efÄH¬Óß4b
Øú, ádú:5b¼2��ÅLÍ1�`qrÎ
{34Ä34Öd4àHÎ1LÍÎ<�JÉc4Ä
Tc1 Å�§J Tc2 ÅA1-�JKàÖú1LÍÎ��É` Ä�3 TG+²b¼2Ó]51vôJ, N
! 4. (a)LÍ0.1 T³Gb�LìIÄA�Lì
I>Jb��ºõ�àÔ6Åj_;-�[6L
bm~b8+�6à(b) LÍ0.1 T, 0.5 T´µ
(c) 2, 3, 4 T³GbM/Hb��ºõ�à
! 5. LÍ0, 1, 2, 3, 5, 9 T³1234�ImCp
b��ºõ�àH6ÅF+Imbù8¡àþ
�!Å�LͳbL×ImCm/T (J»)´µL
×i8<Ì7-Sm(P»)Î�A÷àï6Å�
�õïbLbm~b8+Ë6à
Page 6
b�;¼2��Å�`Lͺõ�ÎpJKà
!6ż2��bLͺõ�ÎpJKH!Gß
4à�5 TGL×efghÓ�;BâMÖdÉ
`4bÓAÏ4à
" (CuBr)Sr2Nb3O10Äé'(Î45lL�bm
���ÓØ`K� , F+Imb�* KGT 3
(KG(GLMNO%P&G0 10>3 J/(K3 mol)) ÎÃ ¡1gâ
JCpÏúzJä áÄ1 :É, !5bþ�!
1pJK Ù1�LÍbL×ImCm / T [J/(mol
K2)]Îù8;¡, Öú1NdÎ8ï÷4áÄ1
:ÉL×i8<Ì7- Sm [J/(mol K)]΢�
Kà Tc2 ´µ Tc1 Gb Sm Å�L×i8<Ì
7-(Rln2)b, Ndæd{b20%, 30%1/�
Ø`àádÅ)b2#Æ�ÄLO6<ª-}�
8ÎyzJÉbáÄGßÏÙà
" Imb�`Lͺõ�1£!J, 0.1 Tÿ-b
LͳGbLM M/H b��ºõ�Î\®Kà!4(c)1pJK Ù1, LÍ2, 3, 4 T§Gb M/H b�6
1�wØW¡-Ó¡Óùɤd4àádúÛ¿Ó[ë4��ÅLÍbg�ÄÝ1Ãð Ø¡, ImG
��údK Tc2 Ä ]�JÉ`4àVK, 1 T ÿ§b÷LͧGÅ, LMìb��¤ï d(M/H)/dT
Ó�øæÎÄ4��Ä Tc2 Ó]�JÉ`4(!4(b))àTc2 ÄÅÈ�ò1 Tc1 GbÛ¿ÎLMb��ºõ
�ÏúÅ�ZGðØ`àádÅ�ú , M1HGÅ�`�ú�Î;:Kõï�efH1Ø:É2¡, Nb
K�LMGÅ)ÉÊefÎyzJKÚTÓùF1 Ø:É`4K�öÄÐâÖd4àHÎ, Q)G
ÅN8N.ºõ�bstÓ :É`4àobN8N.Î�`ÉQSRââ΢Ø:ÉcKÓTc2ÿ§GJ
ÏÛ¿ÓÓâÖdcTVKTIm1Å!51pJKÛ¿ÓTc1G�w1ÅÓâÖdc7-nÓÃð S
Ó:ÉJVÙáÄÓß4à¥I�blkmnÄ^�SÛ�Î�`KââÓ&�b´tGß4à
�BTU�U��k&
ImââG`¦JKDãbefHÅ, LO6<ª-}�8Î]õ§»JK��Ø678ghÓ0^
JKi*.,-MN1õöJÉ`4áÄÎpßJÉ`4à�:É, LÍÎ�F4áÄ1 :É�ÕØ
efHÓ¨�Öd4áÄÓ��Öd41"!7(a)1¸ÁÃ�Û©�b¨.6�+*m<Î�`ÉââJ
K (CuBr)Sr2Nb3O10 bLM M/Ms (Ms Ū«LM) Îp÷àXY=`áÄ1,"*+MÖdKLMNO<
-Ó 2.4 T < H < 8.2 T b¬S�GÓâÖdKàábNO<-Å��b-�ÄÝ1À�w1Ø:É`ð,
Im�LMìG¢�KHUV1ÈøJÉ9 KGuv÷4à!pJÉ`Ø`Ó1.3 KÄ4.2 KbLM�6Å
{ÄUéëGß4áÄÏú, NO<-Ó��1_ú1ØúØ`bÅm�ú�b/0GÅØ , ~�
·¸Î�`K�LMÓ g æbÛE�1 :É_ÁMÖdÉ`4ÄÄ;1Dzialoshinsky-MoriyaH�6
��6�z-ðg~8:.ØUb7ïÓõö÷4ÏúöÄEFúd4àÚ1ÕØbÅ, Q)GÓâÖ
dKLMNO<-Ū«LMb1/3bÄáÏGÓâÖdKáÄGß4à|¿, 1/3LMNO<-Åñ�ò
1a�Îv\ÄJKF+)G3¯ÖdÉ2¡, H�ò1;a�F+bCs2CuBr4�ç[<Q8ðF+b
Cu3(CO3)2OHØUGÓâÖdÉ`4 [10, 11]àJÏJØÓú, LO6<ª-<JKDEF+)12`É
ÅF+ÄbíÐ�bñ�Ïú]¥11/2NO<-JÏ3¯ÖdÉ`Ø`àtu�ÄJÉ, '(edGp
! 6. ImCp(T), LMìM(T)ÄNb��¤ïdM(T)/dT,
LMM(H)1 :ɳúdK(CuBr)Sr2Nb3O10b��>G
LÍH!à
Page 7
ßÖd4Brs+búéÓ
[ë4áÄ1 :Éñ4
òØDEF+Ïúcd ,
©J1 (J2) Ólh®1Ø:
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[12]à�0, ¯�úbñ�
ò��G, $a0^H�
6� J3 (> 0)Î;E°J
KDEF+"µ12`É
1/3LMNO<-ÓIA
d4áÄÓ��ÖdK
[13]àVKT1/3NO<-
ÓIAd4LÍMNbq
�G*�~bmnefH
Óõö÷4áÄ;:�Ö
dÉ2¡, Q)ÄbÈø¬Î\®4K�1ÅÖúØ4H�ò�¢Óî�Gß4à
IöVGbÄáÏ, (CuBr)Sr2Nb3O10 GÓâÖdK1/3LMNO<-b�±Åe�GðÉ`Ø`àJ[
à8«.+678)1234LMb*+M]^Ó²³ú1 :ÉÏ�ÖdÉ`4Ó [14], Nb]^Å
p(S>m) = íã$p = 678ghb}�TS =678ãTm = gQGBÎSéÄJKN[<ßK¡bLM%Ä
â#MÖd, S = 1/2bÍÐ, m = 1/6 Gß4Ïú p = 3 Ó³úd4à(CuBr)Sr2Nb3O10 ÅÛ�M�-bS
éF+15ðCu2+Î]54:É`4bG, *+M]^ÎtY÷41Å2ÑÈx�Óïd4î�Óß4à
!7(b)RG(c)125btuØL×'(Îp÷àé](�G678ÓéëEÌ1Ì`K�L�=Ó, Ndæd
(b)p´«n<.Ók = (2,G/3, 0), (c) k = (,G/3, 2,G/3) G upRGup,GdownRGup, · · · · ·Ä6<O[Ng1_£JÉ
`4àábÔ12`ÉÅ, é�b�L�=ÓupRGdownÄ��1_£JKCAFÎp÷(CuBr)LaNb2O7Ä�
É`4àup>up>down '(bBâ�ÅQ)b�[6��ÓDGß4áÄÄü^جÓß4öÏÙà
VK, obL×'(, 5V¡678bÌðÓ�Éì:K©�L�(Ó c »EÌ1V:É up>up>down
'(ÎÄ:É`4 ÙØ�;EF4áÄ;Gð4àábÍÐ, �0^b(sÄ#0^b(s1ê H
�6�bs1�ÐÓ[ë4áÄÏú, ANNNI(Axial Next>Nearest>Neighbor)QR.G�mNGð4Ï;
ÍdØ`àJÏJ, 16 ÅVKÅ32 ÅNdædÊdK�0^Ä#0^sbÉÊÎE°÷4Ä, 1/3LMNO
<-bS`0 (2.4 < H < 8.2 T) �Ãð`ª«LÍ (Hs = 14.4 T)Îf�÷4áÄÅábQR.GÅÀt
uGßÏÙàL×'(Î��41Å, LͳGb³�+u��NMRââ΢ØÙî�Óß4à
" ��1, M2H15`É�J!®4àLMÅ1/3NO<-MN1µ¡£ q11.6 TG$1g�÷4áÄ
Ïú, ábLÍGý�L�¼2Ó�ðÉ`4ÄeBGð4àdM/dHb7-nÏú¢�Ký�L�¼2
LÍÅ��1¶UºõJØ`(!6)à��LMÓØ`áÄÄ�[6��ÓDGß4áÄÏú, M2HÎ
CAFÄÐâ÷4bÅA4 Ø`àNbÄð, J1#J2QR.1v© Ä, �[6��Ī«LÍbæÏú
J1 = >51.5 K, J2 = 30.6 K, 5V¡J2 / J1 = >0.59 γ4àábJ2 / J1IÅ (CuBr)Sr2Nb3O10 Ó
(CuBr)LaNb2O7 (J2 / J1 = >1.1) ¡;LO6<ª-<JÉ`4áÄÎ�YJÉ`4à5V¡TAN[<
bN[ÜÎúF4áÄ1 :ÉÇ�bF+âãÎúMÖB, NbÛ0 J1 Ä"J2 ;>?Gð4áÄÎ
pJÉ`4à·VÔ(J2 / J1 = >0.50)0e1é`JÉ`4áÄÓ1/3NO<-b8Ib¸ÄØ:É`4bÏ
;ÍdØ .̀
! 7. (a) ª«LMMsGÎFMJK(CuBr)Sr2Nb3O10bLMà
(b), (c) 1/3LMNO<-H1234L×'(bQR.à
Ç�bL×Sé¹ÎÒLGpJÉ`4à
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