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Fig. 3(Color online) Spectra of the intensity of the 006 reectionin the p­schannel at 10 K and X­ray absorption near the Os
L3­edge at room temperature. Excerpt from Ref. 15.

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L3­edge. (b) The temperature dependence of the 006 mag­netic reection in the p­schannel. Excerpt from Ref. 15.

286  úËõ Sept. 2013 Vol.26 No.5

Fig. 5(Color online) (a) Spin arrangements on a regular Os tetra­
hedron for basis functions (Ci) and irreducible representa­
tions (Gj).

gsbNX ¡ 5d JÚà®pCNA_»¨É¨¯éÁÙÈ¥C\¢

Table I

Observed or unobserved conditions for the irreducible representations (IR) and the basis functions in the p­schannel (experimental­
ly observed) and in the p­pchannel (unobserved). Ferromagnetic basis functions C7, C9, and C11 are omitted

IR
Function

G3

G5
c2

c1

G7
c3

G9

c4

c5

c6

c8

c10

c12

Experimental
Result

p­s

obs

obs

obs

obs

unobs

obs

obs

obs

unobs

obs

p­p

unobs

unobs

unobs

unobs

unobs

obs

unobs

obs

unobs

unobs

¢Bµ©µCiqÆ¥CÎÌ«Ìc_©ç³çÉièÞ±ÆÍÂ\Å

éBJÚà®_»¨SÊÉ¨¢ÄCXsÆiqÍCXsO¹ÝìpðÊµÄ­­µÄ¢é½ßCXszñÉ¶½iqÌÎÌ«Ìáºª»êéB
Æ±ëªCæÉq×½iqcÝÉq´È}UÅÍC§û»©çÌÎÌ«áºÌóÍS­Ïª³êÄ¢È¢B]ÁÄC§û»Ì¥CÎÌ«ðL·éàÌðIÑ¾¹ÎÇ¢BÀÍC½­¥«IXszñðL·éîêÌàCC1ÌÝ§û»Ì¥CÎÌ«ÅèC»êÈOÍ³û»Ì¥CÎÌ«ÆÈÁÄ¢éB±êÉæèC±Ì¨¿Ì¥C\¢ÆµÄ C1 Xszñª­­¦´³êéB±Ì C1 ÍC»

Fig. 6(Color online) Time­reversal breaking and resultant
bistability in the all­in/all­out magnetic structure. The
pyrochlore lattice is a corner­linked network of regular tetra­
hedra. The tetrahedron A cannot be superimposed on thetetrahedron B. In (a), all the moments on tetrahedra A point
inwards, while in (b) outwards. The arrangements ofmagnetic moments in (a) and (b) can be regarded as a
macroscopic magnetic octupole, as shown in (c) and (d),respectively.

in Å

éB½ÎÉClÊÌ B ÉÖµÄÍ¥C[gSÌÅ all­in/all­out ÌzñðÆÁÄ¢éBÅßCRàçÍ
P» 17O_NMR ÌÀ±ðs¢CÏªµ½à¥ê·×Äª±ÌXszñN¹Åà¾Å«é±Æð¦µÄ¢é19)BÈ¨C¼Ì 5d JÚà®pCNA R2Ir2O7iR
Nd, EujÉ¨¢ÄàCà®\âÌ]ÚÉº¤XszñÆµÄCIr ãÌ all­in/all­out XszñÌÂ\«ª¦´³êÄ¢é10,20)B

4. ÁÙÈ¥C\¢ªà½ç·àÌ
4.1

Ô½]ÎÌ«ÌjêÌü«Í all­out Ì\¢ÆÈÁÄ¢éB±±ÅCÔ½]
ìð{·ÆC·×ÄÌp^®ÊÌü«ª½]·éBµ½ªÁÄCall­in Å

Á½lÊÌ A Í all­out ÉCall­out ÅX üUC}UCNMR ÌÀ±Ê©çCCd2

Á½lÊÌ B Í all­in ÉüêÖíéiFig. 6(bjjBlÊ

Os2O7 ªà®_âÌ]ÚÆ¯É all­in/all­out ^Ì¥C

Ì A ÆlÊÌ B ÍÀiìÅÍdÈçÈ¢©çCÔ½ðÆé±Æªª©Á½BÉC±Ì¥CÌÁ¥É]ìÌOãÌóÔC·Èí¿Cia)Æ(b)ÍCÀiìÂ¢Äc_·é21)BÎÌ«ÌÏ_©çÍCall­in/all­out ^ÅdÈç¸CIÉÔ½]ÎÌ«ªjê½óÔÆµÄéBæêÉC±Ì¥CÍF¯³êéB¢¢©¦éÆC±Ì¥CóÔÅÍCÔ§û»ÌÎÌ«ðS­jçÈ¢½ßCü`ÌÑ¥¦CUdÌ¥CÍ©ÈèÁêÅ

½]ÎÌ«ÌjêÌÊCñíÞÌ¥ChCª¶Ý·¦CM`±¦CõÌüÜ¦ÈÇÍ®SÉû«ðÛÂ±ÆéB

ª\z³êéB¥CóÔÅ±Ìæ¤È§ûÎÌ«ªc

ÊÌÏ_É§ÄÎCall­in/all­out ¥C\¢ÍCIÈéP[XÍåÏ¿µ¢B½Æ¦ÎCSCjbPCRo

¥CªÉqÆ©È·±ÆàÅ«éB¥CoÉqÍ N ÉÆgÌæ¤È§û»Ì¥«ÌÅ³¦C¥»Ìü«É¶½¥

S ÉÌÎÅ

câCRbg[gøÊÆÄÎêéõwÙû«ªo»

ÉC¥CªÉqÆÍCN ÉÆ S Éð 4 Â¸ÂÀ×½àÌ

µCµ§ÉÍ§ûÎÌ«ªjêéBÅèC±êðIÉ·éÆ¥ÎÆÈéB¯léB8 ÂÌÉÌÀ×ûÉÍ¢­Â©

éªCÅàÎÌ

ÉCall­in/all­out ^Ì¥CªÔ½]ÎÌ«ðj«ÌÇ¢À×ûÍ Figs. 6(c), 6(d)Ìæ¤ÈàÌÅéBÁÄ¢é±Æðà¾µæ¤BpCNAiqð`¬·éall­in/all­out ^Ì¥CÍliqÌ¥CÅé³lÊÌÉÍCñÊèÌü«ªªC»ê¼êÌ¥C[gÌü«ð N ÉÆ S ÉÅ\

éB±êçðÖXIÉl

ÊÌ A, B Æ¼Ã¯éBFig. 6(a)Ì all­in/all­out ¥C·ÆCFigs. 6(c), 6(d)ÌóÔÉÎ·éBall­in/all­out ¥óÔÅÍCOs ãÌ·×ÄÌ¥C[gÍlÊÌ A É

CóÔªL·éÔ½]ÎÌ«ÌjêÆóÔIÈûÖµÄà¤ÌlÊÌSiq111rûüjÖü©ÁÄ¢éB«ÌÛ¶Æ¢¤ 2 ÂÌÁ¥àCI¥CªÉqÆ¢¤·Èí¿lÊÌ A ¾¯©éÆ¥C[gÌü«Í all­`ÆµµÈ¢BÈ¨C8 ÂÌÛÀÉ

éÉÌiNúËõ Sept. 2013 Vol.26 No.5  287

É© S É©jªÖ xyz ÌÆêvµÄ¢é½ßC±ÌªÉqÍ xyz ^ÆÄÎêéB

íÞÌ¥ChCÅtÅ3)éBêÌ¥cÆcÝUNÌ¥»F¥êÌûÊÉæÁ

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4.2\ª³êéÁÙÈoN¨«ÊÆµÄCÍÉæÁÄ¥»ðo»³¹é±ÆàÅ«Ú×ÉÍ§¿üçÈ¢ªCIÈ xyz ^Ì¥CªÉq

éBo»·écÝâ¥»ÌÍCñíÞÌ¥Ch

éÆC©RGlM[Öª HxHyHz, HxEyEz {ExHyªEz{ExEyHz, Hxsyz{Hyszx{Hzsxy ÈÇC§ûÎÌÅ©Â

CÅtÅ
4)

(2) v véÆCM 2v
z x1 E x E y CÔ½]ÉÂ¢ÄïÈðÂ±Æª³êéB±±ÅC
H, E, s ÍC»ê¼êC¥ECdECÍÅêéiFig. 7jB1)v v
é¢ÍCPz2vx(2)2 Ex Hy Ìæ¤ÈÉæÁÄ²gª­¶·éBéB»Ì½ßCOêÉÎ·éÆµÄCÈºÌæ¤È»Ûª\z³éBñÌñü`õwøÊFæñ²g­¶ðáÉÆ±êçÌ»ÛÍÎÌ«ÉîÃ¢Ä\z³êéàÌÅ

ªC÷IÈÏ_É§ÄÎCO¥êÉæé¥C[ñÎÌÈñü`¥»ÈüFq111r²ûüÌ¥» MÆO¥ê H ÌÖWªgÌûüÌÏ»ðl¦é±ÆÅà¾Å«éB¥C[gÌûüªÏ»·é±ÆÅCelÊÌàÌdqÌòÑÚè
ÌoXªöêéB»ÌÊC³¿Å(2)2MxH{x H {céB¥êð c ²É½sÉóÁµÆÈé±Æª\z³êéBx(2) ÌÍCñíÞÌ¥½êÍCFig. 8(a)É¦·æ¤ÉCãÓÉ

ChCÅtÅ

ÌÆºÓÉ

éB

Á½É­ãª¶¶CdqÌhç¬ÌÙû«âClÊÌÌ`ÌÏ»ÉÂÈªéÆl¦éÌÅ2)éé[110]ûü

é[1_10]ûüÌª¿ÅÈ­È¥êÉêÌ¥CUdøÊC¥CïRøÊC¥CéB]ÁÄCUd¦âüÜ¦ÉÙû«ª¶¶éÆÆàÉC

õwøÊFdêÆ¥êÌûÊÉæÁÄÍCUd¦âdab ÊàÉcÝª¶¶éBÜ½CFig. 8(b)Æ(c)É¦·æ¤CïR¦Cé¢ÍõÌ½Ë¦ªCO¥êÉÎµÄêÌÏ»ð¦·±Æª

éB±êçÌWÍCñ

ÉCm111]ûüÉ¥êðóÁµ½êÍC¥êÌ³ÉæÁÄ¥C[gÌpxÏ»ªÙÈèC±êªñü`¥»ßöð¶Ýo·BÜ½CêÊðÍÞ 3 {ÌÆ¼Ì 3{Ìª¿ÅÈ­ÈÁÄ¨èCm111]ûüÌLkâC
Ud¦ÌÙû«ð¶¶³¹éB

4.3

\ÊóÔ

All­in/all­out ¥CÅÍC³lÊÌÌpÌ 4 ÂÌ¥C[gð«µí¹éÆ[ÆÈéÌÅCoN
SÌÆµÄÌ¥»Í[ÅéBµ©µCi111)\Êðl¦éÆCFig. 9(a)Ìæ¤ÉCÅ\ÊÌTCgÌ·×ÄÌ¥C[gªà¤iFig. 7(a) Nonlinear magnetization and (b) linear mag­
netocapacitance, linear magnetostriction, linear magneto­
birefringence predicted for the all­in/all­out magnetic or­dered phase. Solid and dotted lines denote the responses forthe two kinds of magnetic variants.

Fig. 8é¢ÍO¤jðü­±ÆÉÈèC

\Ê¥»ªcéBi111)\ÊÅÍÜê½PhCóÔÌ»ÉÂ¢Äe\ÊÌ¥»ðl¦éÆCFig. 9(b)Ìæ¤É
ÈéB±êÍCIÈ¥CªÉq©çà¼ÏIÉðÅ«éB³çÉC±Ì¥»Æ­¢XsO¹Ýìp©çC(Color online) Changes in the directions of the `all­out' magnetic moments on a tetrahedron. A magnetic eld isapplied in the (a) [001], (b) [111], and (c) [_1 _1 _
1] direction. The six bonds are not equivalent any more, in­ducing several unique physical responses. Excerpt from Ref. 21.

288  úËõ Sept. 2013 Vol.26 No.5

gsbNX ¡ 5d JÚà®pCNA_»¨É¨¯éÁÙÈ¥C\¢Ó«±Ì¤ÍC½­ÌûXÆÌ¤¯¤ðÊµÄÀµ½
àÌÅ·BÖWÒÌûXÉ±ÌêðØèÄ[­´ÓvµÜ·B¤Â X ü¥CUÀ±ÅÍC»w¤Êq¤O[vic¹÷O[vfBN^[jXs
¤`[Ìå÷°KC|ºjC¿cNvCyÑCPxõÈw¤Z^[Ì{MvÉ­ÍÈT|[gð¢½¾«Üµ½BÜ½Cåø¤çCAäPñ
C·JìICFcìÁsCRàêGCëìmCd®©CKcÍGCåìÇTCiª°çÉÀ±sCÊÌðßÉ¨¢Ä¨¢bÉÈèÜµ½B{¤Ì¬ÊÍCÈw¤ïâàC¨æÑC¶ÈwÈu³fíFig. 9(Color online) (a) A {111} surface of the pyrochlore latticewith the all­in/all­out magnetic order. (b) Directions of sur­face magnetization in a crystal of a regular octahedral shapewith a single­domain state of the all­in/all­out magnetic
phase. Surface magnetization normal to each {111} surface
is indicated by arrows. Excerpt from Ref. 21.

ªvWFNgq¤_`¬^rvÌ¬ðó¯Ä¾ç
ê½àÌÅ·B

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iv[vd¬Ì¶ÝàúÒ³êéBÜ½Coh\¢ÉæÁÄÍC\ÊÅ¾¯ohMbvªÂÔêÄñ³à®óÔªcéÂ\«àéBÜ½CñíÞÌhCðuÄé¥ÇÌ«¿ÉÂ¢ÄÍ¤ªÙÆñÇiñÅ¢È¢B¢¸êÉ¹æCÀ±IÉÍCCd2Os2O7 Í¥CÌ`¬ÉæÁÄohMbvªJ¢½æ¤É©¦éÌÅC¥C
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10)Ì«Ìl@©ç¥C\¢ðèµ½B±êÍCÅßÌ 5dnÉ¨¯éÀ±ZpÌiWÉæÁÄà½ç³ê½àÌÅ
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N±µÉ­¢Í¸ÌtXg[giqãÅ¢]Ú·xðÀ»µÄ¢éB¡ñÐîµ½àÌÈOÉàC½Ì»¡éÀ±ªisÅèCå«ÈLªèðúÒµÄ¢éB

16)
17)
18)

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ÒÐî
RY~ê

HÆåwÉ³fíª¤Z^[ÉÁCy³ö
E­mail: jyamauralucid.msl.titech.ac.jpêåF\¢¨«CÅÌ»wmªðn
1997NHÆåwHw¤ÈmÛ
öC¹Cmiw)B1997Nåw¨«¤³C2012Næè»EB

LnF®

åwÉVÌæn¬Èw¤ÈÉ³ö
E­mail: arimak.u­tokyo.ac.jpêåF¨¿Èw
mªðn
1988Nåwåw@Hwn¤ÈCm
ÛöC¹C1994Nmiw)B®
ïÐªq¤CåwwèCåwHwn¤ÈèC}gåw¨¿
Hwn³öCkåw½³¨¿Èw¤
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2007N 4 æè»w¤±B

Peculiar magnetic structure in the 5d ­transition
metal pyrochlore oxideJun­ichi YAMAURA

Materials Research Center of Element Strategy, Tokyo Institute of Technology
Nagatsuta, Yokohama, Kanagawa 226_8503, Japan

Takahisa ARIMA

Graduate School of Frontier Sciences, The University of Tokyo,
Kashiwanoha, Kashiwa, Chiba 277_8561, Japan

Abstract

5d ­transition metal pyrochlore oxide Cd2Os2O7 shows a metal­insulator transition at 227 K withmagnetic ordering. The pyrochlore lattice is composed of the corner­shared tetrahedral Os
network, in which the Os atoms have functions as the electric conduction and/or the magnetic
moment. Since a geometrical frustration between localized spins prevents a long­range magnetic
ordering, a peculiar magnetic structure is expected in the ordered state. We observed a commen­
surate magnetic peak of q (0, 0, 0) by resonant x­ray scattering in a high­quality single crystal.
We propose a noncollinear all­in/all­out spin arrangement on the pyrochlore lattice of Os atoms, inwhich all the spins point to (all­in) or away (all­out) from the centers of the tetrahedron. The mag­
netostriction, magnetocapacitance, Voigt magnetooptic eect, and magnetic susceptibility are
expected to have a term linear to the external magnetic eld.

290  úËõ Sept. 2013 Vol.26 No.5