Guidelines for fabrication of high quality BiFeO...116 Transaction of the Magnetics Society of Japan...
Transcript of Guidelines for fabrication of high quality BiFeO...116 Transaction of the Magnetics Society of Japan...
116 Transaction of the Magnetics Society of Japan (Special Issues) Vol.4, No.2, 2020
INDEXINDEX
T. Magn. Soc. Jpn. (Special Issues)., 4, 116-120 (2020)<Paper>
ååå¿å¿æ§æ§ããã«ã«ã¹ã¹ DDCC ã¹ã¹ããããã¿ã¿ãªãªã³ã³ã°ã°ææèèã«ã«ãããããã BBiiFFeeOO33系系匷匷ç£ç£æ§æ§ïœ¥ïœ¥åŒ·åŒ·èªèªé»é»èèèèã®ã®é«é«ååäœäœäœäœè£œè£œã®ã®ææéé
GGuuiiddeelliinneess ffoorr ffaabbrriiccaattiioonn ooff hhiigghh qquuaalliittyy BBiiFFeeOO33 bbaasseedd
mmuullttiiffeerrrrooiicc tthhiinn ffiillmmss iinn ppuullsseedd DDCC rreeaaccttiivvee ssppuutttteerriinngg mmeetthhoodd
æŠç°èªå€ªæã»å±±æ¬å€§å°ã»åæå²â
ç§ç°å€§åŠ 倧åŠé¢çå·¥åŠç ç©¶ç§ é©æ°ææç 究ã»ã³ã¿ãŒïŒç§ç°çç§ç°åžæ圢åŠåçºïŒâïŒ (ã010-8502)
K. Takeda, D. Yamamoto, and S. Yoshimuraâ Research Center of Advanced Materials for Breakthrough Technology, Graduate School of Engineering Science, Akita University,
1-1 Tegatagakuen-machi, Akita City 010-8502, Japan BiFeO3 based thin films with ferromagnetism were fabricated by using a pulsed DC reactive sputtering method. Guidelines on sputtering targets for fabricating the films are discussed in regard to obtaining high-quality BiFeO3 based thin films. By using a target with a low oxide content (low molar ratio of oxide) and thus good conductivity, it is possible to suppress the charging and arc discharge on the surface of the target and enable high-energy sputtering. As a result, high-quality BiFeO3 based thin films with a high saturation magnetization were formed. By using a target with a high oxygen content (including oxides with a high oxidation valence), the generation of oxygen vacancies that degrade the ferroelectric properties is suppressed, and pinning sites that suppress domain wall movement are then also suppressed. As a result, high-quality BiFeO3 based thin films with good ferromagnetic properties could be formed. KKeeyywwoorrddss:: Multiferroic thin film, pulsed DC reactive sputtering method, sputtering target
11.. ã¯ã¯ããããã«ã« ãã§ã©ã€ããçªåéãªã©ã«ä»£è¡šãããé žåç©ãçªåç©ç£
æ§äœã«ã¯ïŒå€§ããªçµæ¶ç£æ°ç°æ¹æ§ã倧ããªé£œåç£åãªã©ã®
åªããç©æ§ã瀺ããã®ãå€ãïŒBi ãã§ã©ã€ã(BiFeO3)ã¯å®€
æž©ã§åŒ·èªé»ã»å匷ç£æ§ãæãããã«ããã§ãã€ãã¯ç¹æ§ã
æããŠãã 1)ïŒé©æ°çãªæ¬¡äžä»£é»åææãšããŠæåŸ ãããŠ
ããïŒæ¬ææã«ãããŠïŒBi3+ã Ba2+ã§çœ®æããããšã§ Fe3+
ã®äžéšã Fe4+ãšãªãïŒå匷ç£æ§ãããã§ãªç£æ§ãšãªãããš
ã§åŒ·ç£æ§ãšåŒ·èªé»æ§ãçºçŸããããšãå ±åãããŠãã 2)ïŒ
ãŸãïŒFe ã Co ã§çœ®æããããšã«ãã£ãŠã匷ç£æ§ãšåŒ·èªé»
æ§ãçºçŸããããšãå ±åãããŠãã 3), 4)ïŒãã®ãããªåŒ·ç£
æ§â§åŒ·èªé»ææã¯ïŒå°å é»ç E ã«ããç£å M ã®æ¹åå¶åŸ¡ïŒ
å°å ç£å ŽHã«ããé»æ°å極Pã®æ¹åå¶åŸ¡ãå¯èœãšãããŠã
ãããïŒé»çé§ååç£æ°ããã€ã¹ãžã®å¿çšãæåŸ ãããŠã
ã 5), 6), 7), 8)ïŒæã ã®ç 究ã°ã«ãŒãã§ã¯æ¬ææãçšããèè
ãïŒé»çèšé²åã®ããŒããã£ã¹ã¯ãã©ã€ããïŒé»çèšé²å
ã®ç£æ°çŽ°ç·ã¡ã¢ãªãªã©ãžå¿çšããããšãç®æãç 究ãè¡ã£
ãŠããïŒãã®ããã«é»çé§ååã®ç£æ°èšé²ããã€ã¹ã«äœ¿çš
ããå ŽåïŒé«ä¿¡å·åºååãªã©ã®èŠ³ç¹ããé«ã飜åç£åãæ±
ããããïŒä»¥åïŒæ¬ç 究ã°ã«ãŒãã§ã¯ RF ã¹ããã¿ãªã³ã°
æ³ã䜿çšããŠ(Bi,Ba)FeO3 èèãäœè£œããŠãããïŒãã®é£œ
åç£åã®æ倧å€ã¯(Bi,Ba)FeO3 ç²æ«ã®é£œåç£åã®ååçšåºŠ
ã® 60 emu/cm3ãã瀺ããªãã£ã 9)ïŒããã¯(Bi,Ba)FeO3è
èã®çµæ¶åãäžååã§ãã£ãããšãåå ãšèããããïŒã
ãã§ïŒèèãé«åäœã«äœè£œããããïŒRF ã¹ããã¿ãªã³ã°æ³
ã«ä»£ããŠïŒåå¿æ§ãã«ã¹ DC ã¹ããã¿ãªã³ã°æ³ 10) ãçšããŠ
(Bi,Ba)FeO3ç³»èèã®äœè£œãè©Šã¿ãïŒéãã«ã¹é»å§(ïŒ)ãã¿
ãŒã²ããã«åšæçã«å°å ããããšã§ïŒã¿ãŒã²ããè¡šé¢ã®åž¯
é»ã«ããã¢ãŒã¯æŸé»ãæå¶ããïŒè¿å¹Žç¢ºç«ãããææ³ã§ã
ãïŒãã®çµæïŒåå¿æ§ãã«ã¹ DC ã¹ããã¿ãªã³ã°æ³ã§äœè£œ
ããèèã®é£œåç£åã¯ïŒæ倧 92 emu/cm3 ãšãªãïŒå€§å¹ ãª
åäžãèŠãããïŒãŸãïŒåå¿æ§ãã«ã¹ DC ã¹ããã¿ãªã³ã°
æ³ã§äœè£œããèèã¯ïŒRF ã¹ããã¿ãªã³ã°æ³ã§äœè£œããèè
ã«æ¯ã¹ïŒæèé床㯠5 åçšåºŠïŒæµæå€ã¯ 20 åçšåºŠãšãªãïŒ
ä»ã®ç¹æ§ã«é¢ããŠãå€§å¹ ãªåäžãèŠããã 11)ïŒãŸãïŒæ¬æ€
èšã«ãããŠïŒåå¿æ§ãã«ã¹ DC ã¹ããã¿ãªã³ã°æ³ãçšãã
å ŽåïŒæèé»åãé«ãïŒåšæ³¢æ°ãäœãæ¡ä»¶ã§äœè£œãããè
èã®æ¹ãïŒçµæ¶åãä¿é²ããŠããïŒããé«ã飜åç£åã瀺
ããïŒããã¯é«ããšãã«ã®ãŒãæããã¹ããã¿ç²åãé¢æ£
çã«åºæ¿ã«å°éãããããšã§ïŒã¹ããã¿ã OFF ã®éã«åå
ã®åºæ¿è¡šé¢æ¡æ£ãä¿é²ããããã ãšèããããïŒãã®åå¿
æ§ãã«ã¹ DC ã¹ããã¿ãªã³ã°æ³ã«ãããŠïŒRF ã¹ããã¿ãªã³
ã°æ³ã§äœ¿çšããŠãã絶çžäœã§ããïŒBi-Ba-Fe-O ã¿ãŒã²ãã
ãçšããŠèèäœè£œãè¡ããšïŒã¿ãŒã²ããã®æµæãéåžžã«å€§
ããããšããïŒãã©ãºãçç«æã®ã¿ãªãããã©ãºãçç«åŸ
ã«ãããŠãéåžžã«å€ãã®ã¢ãŒã¯æŸé»ãçããïŒããã«å ã
ãŠïŒäœè£œããèèã«ãã㊠Bi ããŸã£ããå«ãŸããïŒäœè£œã
ããçµæã®èèãäœè£œã§ããªãã£ãïŒãã®ããïŒå ã®å®éš
ã§ã¯ïŒç¹å¥ã«äœè£œããå°é»æ§ã® Ba-Fe-O ã¿ãŒã²ããã« Biã·ãŒããé 眮ãããã®ãçšããŠèèäœè£œãè¡ã£ãïŒãã£ãŠïŒ
åå¿æ§ãã«ã¹ DC ã¹ããã¿ãªã³ã°æ³ã«ãããã¿ãŒã²ããã®
詳现ãªæ€èšãå¿ èŠãšãªã£ãŠããïŒ äžæ¹ã§ïŒå°é»æ§ã®ã¿ãŒã²ãããçšããŠé žåç©èèãäœè£œ
ããå ŽåïŒèèäžã«ãããŠé žçŽ æ¬ æãçãããããªãããš
ãæžå¿µãããïŒBiFeO3ç³»èèã®é žçŽ æ¬ æã¯ïŒèªé»ç¹æ§ãå£
åãããããšãå ±åãããŠãã 12)ïŒãã®ç¹æ§ã¯ïŒé»çé§å
åã®ç£æ°èšé²ããã€ã¹ãžã®å¿çšã«ããããŠéèŠã§ããïŒé
åžžã® DC é»æºããã³æ¬ãã«ã¹ DC é»æºãçšããå Žåã®åå¿
117Transaction of the Magnetics Society of Japan (Special Issues) Vol.4, No.2, 2020
INDEXINDEX
æ§ã¹ããã¿ãªã³ã°æèã«ãããŠïŒèèäžé žçŽ æ¿åºŠãå¢å€§ã
ããŠé žçŽ æ¬ æãæå¶ããææ³ã®ã²ãšã€ãšããŠïŒæèããã»
ã¹ã¬ã¹ã«ãããé žçŽ åå§ãå¢å€§ãããããšãæãããããïŒ
Ar ãš O2 ã®åå§æ¯ã 7ïŒ3 ã§æèããå Žåã®æèé床ã¯
0.0733 nm/s ã§ãã£ãã®ã«å¯ŸãïŒ5ïŒ5 ã§æèããå ŽåïŒæ
èé床㯠0.0380 nm/s ãšååçšåºŠãšãªãïŒé žçŽ åå§ã®å¢å€§
ã«äŒŽãæèé床ãé ããªãããšãå€ã£ãïŒãŸãïŒ5ïŒ5 ã§æ
èããå Žåã§ã¯ïŒèèäžã® Bi å«æéããŒããšãªãïŒèèçµ
æã®å¶åŸ¡ã極ããŠé£ãããªããªã©ã®åé¡ãèŠãããïŒä»¥äž
ã®ããšããïŒæèããã»ã¹ã¬ã¹ã«ãããé žçŽ ã®å°å ¥ã¯ïŒArãš O2ã®åå§æ¯ã§ 7ïŒ3 ãéçã§ãããšèšãïŒæèããã»ã¹
äžã®é žçŽ åå§ã®å¢å€§ä»¥å€ã®ææ³ã§ã®èèäžé žçŽ æ¿åºŠã®å¢å€§
ãå³ãå¿ èŠãããïŒ
ããã§æ¬ç 究ã§ã¯ïŒåå¿æ§ãã«ã¹ DC ã¹ããã¿ãªã³ã°æ³
ã«ãããŠäœè£œãããèèã§ã®ïŒãã©ãºãå®å®æ§ããã³ç£æ°
ç¹æ§ã«ãããã¿ãŒã²ããå°é»æ§äŸåãæããã«ããããšãšïŒ
èèã®ç£æ°ã»èªé»ç¹æ§ã«ãããã¿ãŒã²ããäžé žçŽ æ¿åºŠäŸå
ãæããã«ããããšãç®çãšããïŒããã«ãã£ãŠïŒåŒ·ç£æ§ã»
匷èªé» BiFeO3 ç³»èèã®ãã«ã¹ DC ã¹ããã¿ãªã³ã°æèã«
ãããé«åäœäœè£œã®æéãã§ãïŒããå¹ççã«é«åäœã®è
èãäœè£œã§ããããã«ãªããšæåŸ ã§ããïŒ
22.. å®å®éšéš
22..11 å°å°é»é»æ§æ§ã®ã®ç°ç°ãªãªããã¹ã¹ããããã¿ã¿ãªãªã³ã³ã°ã°ã¿ã¿ãŒãŒã²ã²ããããããçšçšããããå Žå Ž
ååã®ã®èèèèäœäœè£œè£œ
(Bi,Ba)FeO3(BBFO)èè(èå 200 nm)ãïŒåå¿æ§ãã«ã¹
DC ã¹ããã¿ãªã³ã°æ³ãçšããŠïŒç±é žåèä»ã Si åºæ¿äžã«
Ta(5 nm)/Pt(100 nm)ã®äžå°å±€ 13) ãæèããåŸïŒç©å±€èãš
ããŠäœè£œããïŒç©å±€èã¯åºæ¿æž©åºŠãšããŠïŒTa ã宀枩ïŒPtã 300âïŒBBFO ã 695âã§æèããïŒããã«ïŒBBFO è
èã®ãããã¹ã«ã€ãæ§é ã®åœ¢æãä¿é²ãããããã«ïŒæè
æã®èèã« VHF ãã©ãºãç §å°ãæœããïŒBBFO èèã®æ
èã«ã¯ïŒFe ç²æ«ãš Ba-Fe-Oç²æ«ãšãçŒçµãããŠäœè£œããïŒ
é žåç©ã®å«æéãç°ãªã(å°é»æ§ãç°ãªã)3 çš®é¡ã®ã¿ãŒã²
ããã«ïŒBi ã·ãŒããé 眮ãããã®ãçšããïŒããããã®ã¿
ãŒã²ããã«å«ãŸããé žåç©å«æéã®å²åã¯ïŒ14, 17, 20 mol%ã§ãã(ããããã®ã¿ãŒã²ããåã䟿å®äž Ox-14ïŒOx-17ïŒOx-20 ãšãã)ïŒã¹ããã¿ãªã³ã°é»æºã«ã¯ ULVAC瀟補ã®åå¿æ§ SPUTTER çš DC PULSE é»æº DPG-5P ã
çšããïŒãã«ã¹åšæ³¢æ°ããã³éãã«ã¹å°å (ã¹ããã¿ OFF)æéãïŒ5ïœ250ïœHz ããã³ 0.4ïœ5 ÎŒs ã®ç¯å²ã§å€åããã
ããšãã§ããæ¬é»æºã¯ïŒã¢ãŒã¯æŸé»ã®åæ°ãã«ãŠã³ãã§ã
ãæ©èœãæããŠããïŒåå¿æ§ãã«ã¹ DC ã¹ããã¿ãªã³ã°æ³
ã«ããããã«ã¹æ¡ä»¶ãšããŠïŒåšæ³¢æ°ã 200 kHzïŒé»åã 150 WïŒONïŒOFF æ¯ã 3ïŒ2 ã§åºå®ããŠæèãè¡ã£ãïŒæèã
ãã»ã¹ã¬ã¹ã«ããã Ar ãš O2 ã®åå§æ¯ã¯åèšã®èŠ³ç¹ãã
7ïŒ3 ã§åºå®ãïŒå šå§ã 10 mTorr ãšããïŒ
22..22 é žé žçŽ çŽ æ¿æ¿åºŠåºŠã®ã®ç°ç°ãªãªããå°å°é»é»æ§æ§ã¹ã¹ããããã¿ã¿ãªãªã³ã³ã°ã°ã¿ã¿ãŒãŒã²ã²ãããããã
çšçšããããå Žå Žååã®ã®èèèèäœäœè£œè£œ
(Bi,Gd)(Fe,Co)O3(BGFCO)èè(èå 200 nm) ãïŒåå¿
æ§ãã«ã¹ DC ã¹ããã¿ãªã³ã°æ³ãçšããŠïŒBBFO èèã®å Ž
åãšåæ§ã®ç©å±€æ§é ããã³åºæ¿æž©åºŠïŒVHF ãã©ãºãç §å°ã«
ããäœè£œããïŒBi ãã§ã©ã€ã(BiFeO3)ã® Bi ã Gd ã§çœ®æ
ããããšã«ãã£ãŠã匷ç£æ§ã»åŒ·èªé»ãçºçŸããããšãå ±å
ãããŠãã 14)ïŒBGFCO èèã®æèã«ã¯ïŒGd-Fe-O ç²æ«ïŒ
Fe ç²æ«ïŒCo ç²æ«ãçŒçµãããŠäœè£œããå°é»æ§ã¿ãŒã²ãã
ã«ïŒBi ã·ãŒããé 眮ãããã®ãçšããïŒäœ¿çšããã¿ãŒã²ã
ãã®çµæã¯ïŒFe ç²æ«ïŒCo ç²æ«ïŒGdFeO3 ç²æ«ã 7ïŒ3ïŒ2ã® mol æ¯ã§æ··åãããŠçŒçµäœè£œããã¿ãŒã²ãã(G1O3)ãšïŒ
Fe ç²æ«ïŒCo ç²æ«ïŒGd3Fe5O12ç²æ«ã 8ïŒ4ïŒ1 ã® mol æ¯ã§
æ··åãããŠçŒçµäœè£œããã¿ãŒã²ãã(G1O4)ã®2çš®ãçšããïŒ
åå¿æ§ãã«ã¹ DC ã¹ããã¿ãªã³ã°æ³ã«ããããã«ã¹æ¡ä»¶ãš
ããŠïŒåšæ³¢æ°ã 100 kHzïŒé»åã 150WïŒONïŒOFF æ¯ã
3ïŒ2 ã§åºå®ããŠæèãè¡ã£ãïŒ
22..33 èèèèã®ã®ç¹ç¹æ§æ§è©è©äŸ¡äŸ¡
äœè£œããèèã®çµæåæã¯ïŒãšãã«ã®ãŒåæ£å X ç·åå
åš(EDS)ã«ããïŒç£æ°æž¬å®ã¯ïŒæ¯åè©Šæåç£åèš(VSM)ã«ããïŒçµæ¶æ§é ããã³çµæ¶æ§ã®è©äŸ¡ã¯ XRD ã«ããè¡ã£ãïŒ
èªé»æž¬å®ã¯ïŒBGFCOç©å±€èã®æè¡šé¢ã« Ptãããç¶é»æ¥µ(Ï100 µm)ãæèããåŸã«ïŒåŒ·èªé»äœç¹æ§è©äŸ¡ã·ã¹ãã ã«ã
ãè¡ã£ãïŒ
33.. çµçµææ 33..11 èèèèã®ã®çµçµæ¶æ¶æ§æ§é é ïŒïŒç£ç£æ°æ°ç¹ç¹æ§æ§ããããã³ã³ããã©ã©ãºãºããå®å®å®å®æ§æ§ã«ã«ãã
ããããã¹ã¹ããããã¿ã¿ãªãªã³ã³ã°ã°ã¿ã¿ãŒãŒã²ã²ããããå°å°é»é»æ§æ§äŸäŸåå
åè¿°ã®éãïŒåå¿æ§ãã«ã¹ DC ã¹ããã¿ãªã³ã°æ³ã§ã¯ïŒ
éãã«ã¹é»å§(ïŒ)ã®å°å ã«ããã¿ãŒã²ããè¡šé¢ã®åž¯é»ãæ
å¶ããå¹æãããããïŒã¿ãŒã²ããã«ã¯å°é»æ§ãæããã
ãšãå¿ èŠã§ãããïŒã©ã®çšåºŠã®å°é»æ§ãå¿ èŠãã«ã€ããŠã¯ïŒ
å šãããã£ãŠããªãïŒããããµãŸããŠïŒèèã®çµæ¶æ§é ïŒ
ç£æ°ç¹æ§ããã³æèäžã®ãã©ãºãå®å®æ§ã«ãããã¿ãŒã²ã
ãå°é»æ§ã®äŸåæ§ã調ã¹ãïŒ
ãŸãïŒå Ox-14ïŒOx-17ïŒOx-20 ã¿ãŒã²ããã«ãããã·
ãŒãæµæã枬å®ããçµæïŒæ°Î©/sqïŒæ°åΩ/sqïŒæ° kΩ/sqçšåºŠã§ãã£ãïŒæ¬¡ã«ïŒå°é»æ§ãç°ãªãå Ox-14ïŒOx-17ïŒ
FFiigg.. 11 XRD profiles of Bi-Ba-Fe-O films on Ta/Pt layer fabricated with various sputtering targets.
118 Transaction of the Magnetics Society of Japan (Special Issues) Vol.4, No.2, 2020
INDEXINDEX
Ox-20 ã¿ãŒã²ãããçšããŠäœè£œããèèã®ïŒçµæïŒçµæ¶æ§
é ã®è©äŸ¡ãè¡ã£ãïŒEDS ã«ããçµæåæã®çµæã¯ïŒOx-14㿠㌠㲠ã ã ã çš ã ãŠ äœ è£œ ã ã è è 㧠㯠ïŒ
(Bi0.46Ba0.54)0.35Fe0.65OxïŒOx-17 ã¿ãŒã²ãããçšããå Žåã§
ã¯ïŒ (Bi0.50Ba0.50)0.40Fe0.60OxïŒOx-20 ã¿ãŒã²ãããçšãã
å Žåã§ã¯ïŒ(Bi0.49Ba0.51)0.44Fe0.56Ox ãšãªã£ãïŒãŸãïŒFig.1ã«ãããã®èèã® XRD ã«ããçµæ¶æ§é ã®è©äŸ¡çµæã瀺ãïŒ
å³äžã®è²ä»ããããé åã(Bi,Ba)FeO3(001)ã®åæããŒã¯
ã§ããïŒãã以å€ã®(Bi,Ba)FeO3 ã®åæããŒã¯ã¯èŠ³æž¬ãã
ãªãã£ãïŒãããã®ããšããïŒãããã®ã¿ãŒã²ããã§äœè£œ
ããèèã«ãããŠãïŒBiFeO3ç³»åçžèèã圢æãããŠããïŒ
ãã€ïŒé žåç©å«æéãå°ãªãå°é»æ§ãé«ãã¿ãŒã²ãããçš
ããããšã«ããïŒçµæ¶æ§ãåäžããããšã確èªãããïŒ
Fig.2 ã«ïŒå°é»æ§ãç°ãªãã¿ãŒã²ããïŒOx-14ïŒOx-17ïŒOx-20 ãçšããŠäœè£œããèèã®é£œåç£åã®ã¿ãŒã²ããäžé ž
åç©å«æéäŸåæ§ã瀺ãïŒé žåç©å«æéãå°ãªãå°é»æ§ã
é«ãã¿ãŒã²ãããçšãããšé£œåç£åã¯é«ãå€ã瀺ãïŒãã®
å€ã¯ 62 emu/cm3ã ã£ãïŒãªãïŒéå»ã®æã ã®å®éšçµæ 11) ã«
察ããŠé£œåç£åãå°ããçç±ã¯ïŒä»åçšãããã«ã¹åšæ³¢æ°
ãæé©å€ããé«ããŠçµæ¶åã®ä¿é²ãäžå®å šã§ãã£ããããš
èããããïŒãããŠïŒå°é»æ§ãæªããªããšïŒé£œåç£åã¯æ¥
æ¿ã«æžå°ãïŒåå以äžã®å€ã«ãªã£ãïŒ å°é»æ§ãæªããªããšé£œåç£åãæžå°ããèŠå ã調ã¹ã
ããã«ïŒé»æºã«ä»å±ã®ã¢ãŒã¯æŸé»ã®åæ°ãã«ãŠã³ãã§ãã
æ©èœãçšãïŒåã¿ãŒã²ãããçšããæã®ãã©ãºãã®å®å®æ§
ã調ã¹ãïŒOx-14 ã¿ãŒã²ããã®å Žåã§ã¯ïŒãã©ãºãçç«æ
ããã³ãã©ãºãçç«åŸã«ãããŠãã¢ãŒã¯æŸé»ã¯å šãã«ãŠã³
ããããªãã£ããïŒã¿ãŒã²ããäžã®é žåç©å«æéãå€ãå°
é»æ§ãäœã Ox-17ïŒOx-20 ã¿ãŒã²ããã®å Žåã§ã¯ïŒãã©ãº
ãçç«çŽåŸã®æ°ç§éã«æ°ååïŒãã©ãºãçç«ä»¥éã«ãããŠ
ãæç¶çã«æ°çŸåã®ã¢ãŒã¯æŸé»ã芳枬ãããïŒãããã®ã
ãšããïŒã¿ãŒã²ããã«å°é»æ§ããã£ãŠãïŒãã®å€ãäœãå Ž
åã§ã¯ïŒéãã«ã¹é»å§(ïŒ)ã®å°å ã«ãã£ãŠãã¿ãŒã²ããè¡š
é¢ã®åž¯é»ãå®å šã«æå¶ããããšã¯åºæ¥ãªãããšïŒãã®åž¯é»
ã«ããé«ãšãã«ã®ãŒã®ã¹ããã¿ç²åãçæãããã«çµæ¶å
ãé»å®³ãããããšã瀺åãããïŒãŸãïŒã¢ãŒã¯æŸé»ã®çºç
ã¯ïŒããã€ã¹ã®è£œé ãèããéïŒæ¬ é¥éšã®çæãåå ãšã
ãäžå®å šåäœãäžè¯åãçºçãããããªã©ã®åé¡ã«çºå±ã
ãæãããã芳ç¹ãããïŒã§ããã ãçºçãæå¶ããå¿ èŠ
ããããšæãããïŒ
以äžããïŒæ¬åå¿æ§ãã«ã¹ DC ã¹ããã¿ãªã³ã°æ³ã«ãã
ãŠïŒã§ããã ãå°é»æ§ã®è¯ãã¿ãŒã²ãããçšããããšã§ïŒ
ã¿ãŒã²ããè¡šé¢ã§ã®åž¯é»ãã¢ãŒã¯æŸé»ãæå¶ãããããšã
ãïŒçµæ¶æ§ãè¯ãé«åäœãªèèã圢æããïŒé«ã飜åç£å
ã瀺ãèèãäœè£œã§ãããšèããããïŒ
33..22 èèèèã®ã®çµçµæ¶æ¶æ§æ§é é ããããã³ã³ç£ç£æ°æ°ã»ã»èªèªé»é»ç¹ç¹æ§æ§ã«ã«ããããããã¹ã¹ãããã
ã¿ã¿ãªãªã³ã³ã°ã°ã¿ã¿ãŒãŒã²ã²ããããäžäžé žé žçŽ çŽ æ¿æ¿åºŠåºŠäŸäŸåå
ãããŸã§ã®è°è«ããïŒã¿ãŒã²ããã«ã¯ïŒå°é»æ§ãé«ãïŒ
ã€ãŸãã¿ãŒã²ããäžé žåç©å«æé (é žåç©ã® mol) æ¯ãå°
ãªããã®ãè¯ãããšãããã£ãïŒããããªããïŒã¿ãŒã²ã
ãäžé žåç©å«æéãåçŽã«æžå°ããããšïŒèèäžé žçŽ æ¬ æ
ãçãããããªãããšãæžå¿µãããïŒãã®åœ±é¿ã調ã¹ãã
ãã«ïŒã¿ãŒã²ããã®äœè£œæã«çšããé žåç©ã® mol æ¯ãå°ãª
ãç¶æããªããïŒé žå䟡æ°ãç°ãªãé žåç©(GdFeO3ç²æ«ã
ãã³ Gd3Fe5O12 ç²æ«)ãçšããã¿ãŒã²ãã(G1O3 ããã³
G1O4)ãäœè£œããŠå®éšãè¡ã£ãïŒ
3.1 ã® BBFO èèãšåæ§ã«ïŒãŸãïŒå G1O3ïŒG1O4 ã¿
ãŒã²ããã«ãããã·ãŒãæµæã枬å®ããçµæïŒããããæ°
Ω/sq çšåºŠã§ãã£ãïŒæ¬¡ã«ïŒé žçŽ æ¿åºŠãç°ãªãåã¿ãŒã²ãã
ãçšããŠäœè£œããèèã®ïŒçµæïŒçµæ¶æ§é ã®è©äŸ¡ãè¡ã£ãïŒ
EDS ã«ããçµæåæã®çµæã¯ïŒG1O3 ã¿ãŒã²ãããçšããŠ
äœè£œããèèã§ã¯ïŒ (Bi0.48Gd0.52)0.36(Fe0.75Co0.25)0.64OxïŒ
G1O4 㿠㌠㲠ã ã ã çš ã ã å Ž å 㧠㯠ïŒ
(Bi0.52Gd0.48)0.36(Fe0.75Co0.25)0.64Ox ãšãªã£ãïŒãŸãïŒFig.3ã«ãããã®èèã® XRD ã«ããçµæ¶æ§é ã®è©äŸ¡çµæã瀺ãïŒ
å³äžã®è²ä»ããããé åã(Bi,Gd)(Fe,Co)O3(001)ã®åæ
ããŒã¯ã§ããïŒãã以å€ã®(Bi,Gd)(Fe,Co)O3 ã®åæããŒã¯
ã¯èŠ³æž¬ãããªãã£ãïŒãããã®ããšããïŒãããã®ã¿ãŒã²
ããã§äœè£œããèèã«ãããŠãïŒBiFeO3ç³»åçžèèã圢æ
FFiigg.. 22 Dependence of saturation magnetization of (Bi,Ba)FeO3 films on oxide content in sputtering target.
FFiigg.. 33 XRD profiles of Bi-Gd-Fe-Co-O films on Ta/Pt layer fabricated with various sputtering targets.
119Transaction of the Magnetics Society of Japan (Special Issues) Vol.4, No.2, 2020
INDEXINDEX
ãããŠããïŒãã€ïŒé žçŽ æ¿åºŠãé«ãã¿ãŒã²ãããçšããã
ãšã«ããïŒçµæ¶æ§ãåäžããããšã確èªãããïŒ
Fig.4ïŒFig.5 ã«ïŒé žçŽ æ¿åºŠã®ç°ãªã 2 ã€ã®ã¿ãŒã²ããã
çšããŠäœè£œãã BGFCO èèã®èé¢å ããã³åçŽæ¹åã®ç£
åæ²ç·ã瀺ãïŒé£œåç£åã¯ãããã®èèè©Šæã«ãããŠãïŒ
80 emu/cm3çšåºŠã®æ¯èŒçé«ãå€ãåŸãããïŒä¿ç£åã«é¢ã
ãŠã¯ïŒãããã®èèè©Šæã«ãããŠãïŒèé¢åçŽæ¹åã«å€§ã
ãªä¿ç£åãåŸããããïŒé žçŽ æ¿åºŠãé«ã G1O4 ã¿ãŒã²ãã
ãçšããŠäœè£œããèèã®æ¹ãå°ããå€ã瀺ããïŒFig.6ïŒFig.7 ã«ïŒåèèã®èªé»ç¹æ§ã瀺ãïŒG1O3 ã¿ãŒã²ãããçš
ããŠäœè£œããèèã§ã¯ïŒæçãªãã¹ããªã·ã¹ã確èªã§ããª
ãã£ãããšããïŒåžžèªé»æ§ãæããŠãããšæãããïŒãŸãïŒ
å³ã«ã¯ç€ºããŠããªããïŒåäžèèè©Šæå ã®å¥çŽ åã®æž¬å®ã«
ãããŠã¯ïŒå°å é»çã倧ããããéäžã«ãããŠçµ¶çžç Žå£ã
ãã°ãã°èµ·ããåŸåãèŠãããïŒäžæ¹ã§ïŒG1O4 ã¿ãŒã²ã
ããçšããå Žåã®èèã§ã¯ïŒå³ã«ç€ºããçŽ åãå«ãã»ãšã
ã©ã®çŽ åã«ãããŠåç¹å¯Ÿç§°æ§ãè¯ãæçãªãã¹ããªã·ã¹ã
åŸãããããšããïŒåŒ·èªé»ç¹æ§ã瀺åãããïŒäœ¿çšããã¿
ãŒã²ããã«ãã匷èªé»ç¹æ§ã®éããçããèŠå ãšããŠïŒé ž
çŽ æ¿åºŠãé«ã G1O4 ã¿ãŒã²ãããçšããŠç©æ¥µçã«é žçŽ ãäŸ
絊ããªããæèãããè©Šæã§ã¯ïŒçµæ¶æ§ãåäžããŠããã
ãšããïŒåŒ·èªé»ç¹æ§ãå£åãããé žçŽ æ¬ æã®çºçãæå¶ã
ããããã§ãããšèããããïŒãããŠïŒãã®é žçŽ æ¬ æã®äœ
æžãïŒå€éšç£å Žã«å¯Ÿããç£å£ç§»åãæå¶ãããã³ãã³ã°ãµ
ã€ãã®äœæžãããããïŒFig. 5 ã§ç€ºããããã«ä¿ç£åãå°
ãããªã£ããšèããããïŒ
以äžããïŒæ¬åå¿æ§ãã«ã¹ DC ã¹ããã¿ãªã³ã°æ³ã«ãã
ãŠïŒå°é»æ§ãé«ãé žçŽ æ¿åºŠã®é«ãã¿ãŒã²ãããçšããããš
ãïŒé«ã飜åç£åããã³åŒ·èªé»ç¹æ§ãæåŸ ãããïŒé«åäœ
ãªèèã圢æã§ããæ¡ä»¶ã§ãããšãããïŒ
44.. ãŸãŸãšãšãã åå¿æ§ãã«ã¹ DC ã¹ããã¿ãªã³ã°æ³ãçšããŠé«åäœãªåŒ·
ç£æ§ïœ¥åŒ·èªé»èèãäœè£œããã«ãããïŒã¹ããã¿ãªã³ã°ã¿ãŒ
ã²ããã«ãããŠïŒä»¥äžã®æéãåŸãïŒ
ïŒïŒé žåç©å«æé(é žåç©ã® mol æ¯)ãå°ãªãå°é»æ§ã®è¯
ãã¿ãŒã²ãããçšããããšã«ããïŒã¿ãŒã²ããè¡šé¢ã®åž¯é»
ãã¢ãŒã¯æŸé»ãæå¶ããŠïŒé«ããšãã«ã®ãŒã§ã®ã¹ããã¿ãª
ã³ã°ãå¯èœã«ãªãçµæïŒé«åäœãªèèã圢æããïŒé«ã飜
åç£åã瀺ãèèãäœè£œã§ããïŒãšèããããïŒ
FFiigg.. 66 P-E curves of (Bi,Gd)(Fe,Co)O3 film fabricated with target G1O3.
FFiigg.. 77 P-E curves of (Bi,Gd)(Fe,Co)O3 film fabricated with target G1O4.
FFiigg.. 55 M-H curves (red line: out-of-plane, blue line: in-plane) of (Bi,Gd)(Fe,Co)O3 film fabricated with target G1O4.
FFiigg.. 44 M-H curves (red line: out-of-plane, blue line: in-plane) of (Bi,Gd)(Fe,Co)O3 film fabricated with target G1O3.
120 Transaction of the Magnetics Society of Japan (Special Issues) Vol.4, No.2, 2020
INDEXINDEX
ïŒïŒé žçŽ æ¿åºŠãé«ã(é žå䟡æ°ã®é«ã)ã¿ãŒã²ãããçšã
ãããšã«ããïŒåŒ·èªé»ç¹æ§ãæåŸ ãããïŒãã€å°ããªä¿ç£
åãåŸãããïŒçµæ¶æ§ã®è¯ãé«åäœãªèèãäœè£œã§ããïŒ
ããã¯ïŒåŒ·èªé»ç¹æ§ãå£åãããé žçŽ æ¬ æã®çºçãæå¶ã
ãïŒç£å£ç§»åãæå¶ãããã³ãã³ã°ãµã€ãã®äœæžãåå ã§
ãããšèããããïŒ
References 1) G. A. Smolenskii and D. H. Wang: Chupis, Sov. Phys. Usp., 2255,
475 (1982). 2) D. H. Wang, W. C. Goh, M. Ning, and C. K. Ong: Appl. Phys.
Lett., 8888, 212907 (2006). 3) D. G. Barrionuevo, S. P. Singh, R. S. Katiyar, and M. S.
Tomar: MRS Proc., 11225566, 1256-N06-47 (2010). 4) H. Hojo, R. Kawabe, K. Shimizu, H. Yamamoto, K. Mibu, K.
Samanta, T. Saha-Dasgupta, and M. Azuma: Advanced Materials, 2299, 1603131 (2017).
5) T. Kimura, T. Goto, H. Shinatani, K. Ishizaka, T. Arima, and Y. Tokura: Nature, 442266, 55 (2003).
6) N. Hur, S. Park, P. A. Sharma, J. S. Ahn, S. Guha, and S.-W. Cheong: Nature 442299, 392 (2004).
7) J. Wang, J. B. Neaton, H. Zheng, V. Nagarajan, S. B. Ogale, B. Liu, D. Viehland, V. Vaithyanathan, D. G. Schlom, U. V. Waghmare, N. A. Spaldin, K. M. Rabe, M. Wuttig, and R. Ramesh: Science, 229999, 1719 (2003).
8) W. Prellier, M. P. Singh, and P. Murugavel, J. Phys.: Condens. Matter, 1177, R803 (2005).
9) S. Yoshimura, Y. Sugawara, G. Egawa, and H. Saito: Journal of the Magnetics Society of Japan, 4422, 11 (2018).
10) D. R. Pelleymounter, D. J. Christie, and B. D. Fries: 57th Annu. Technical Conf. Proc., 183 (2014).
11) S. Yoshimura, and M. Kuppan: Japanese Journal of Applied Physics, Selected Topics in Applied Physics, 5577, 0902B7 (2018).
12) X. Qi, J. Dho, R. Tomov, M. G. Blamire, and J. L. MacManus-Driscoll: Appl. Phys. Lett., 8866, 062903 (2005).
13) Y. Takeda, S. Yoshimura, M. Takano, H. Asano, and M. Matsui: J. Appl. Phys., 110011, 09J514 (2007).
14) A. Ablat, R. Wu, M. Mamat, J. Lia, E. Muhemmed, C. Si, R. Wu, J. Wang, H. Qian, K. Ibrahim: Ceramics International, 4400 14083 (2014).
22001199幎幎1111ææ77æ¥æ¥ååççïŒïŒ22002200幎幎77ææ1166æ¥æ¥æ¡æ¡é²é²