2011A1698

  BL17SU

ᆶ┤☢໬ᆺ☢ቨ⛣ື࣓ࣔࣜ⏝☢ᛶ⣽⥺ࡢ☢ቨ㟁ὶ㥑ືࡑࡢሙほᐹObservation of current induced domain wall motion in magnetic wires fordomain wall motion memory with perpendicular magnetic anisotropy㇂ᕝ ༤ಙ a, ኱ᔱ ๎࿴ a, ᑠᒣ ▱ᘯ b, ༓ⴥ ኱ᆅ b, ᑠ㔝 ㍤⏨ b, ᑠႹ ┿ே c, ኱Ἑෆ ᣅ㞝 c
Hironobu Tanigawaa, Norikazu Ohshimaa, Tomohiro Koyamab, Daichi Chibab, Teruo Onob,
Masato Kotsugic, Takuo Ohkochicaࣝࢿࢧࢫ࢚ࣞࢡࢺࣟࢽࢡࢫᰴᘧ఍♫, b ி㒔኱Ꮫ໬Ꮫ◊✲ᡤ, cJASRI/SPring-8
aRenesas Electronics Corp., bKyoto University, cJASRI/SPring-8☢ቨ㟁ὶ㥑ືࢲ࢖ࢼ࣑ࢡࢫࡢゎ᫂࠾ࡼࡧ☢ቨ⛣ື࣓ࣔࣜࡢᇶᮏືసゎᯒࡢ୍⎔࡜ࡋ࡚ࠊ
SPELEEM ࢆ⏝࠸ࡓ Co/Ni ᆶ┤☢໬⣽⥺୰࡟ᙧᡂࡋࡓ☢ቨࡢ㟁ὶ㥑ື⌧㇟ほᐹࢆ࠾ࡇ࡞ࡗ࡚࠸ࡿࠋ
2011A ᮇࡣࠊྠ୍⣲Ꮚ࡟࠾ࡅࡿ☢ቨ⛣ື㏿ᗘ࡜ࡤࡽࡘࡁ࡟ࡘ࠸࡚㆟ㄽࡍࡿࡓࡵ࡟ࠊ☢ቨᑟධ࠾ࡼࡧ☢ቨ⛣ືࡢࡓࡵࡢ㟁ὶ༳ຍࡀ SPELEEM ⿦⨨ෆ࡟࡚⾜࠼ࡿࡼ࠺࡞ ᐃ⎔ቃࢆᵓ⠏ࡍࡿࡇ࡜ࢆヨࡳࡓࠋࡑࡢ⤖ᯝࠊ㟁ὶ☢ሙࢆⓎ⏕ࡉࡏࡿࡇ࡜࡛ Co/Ni ⣽⥺ෆ࡟☢ቨࢆᑟධྍ⬟࡛࠶ࡿࡇ࡜ࢆᐇドࡋࡓࠋほᐹ࡟ࡣ BL17SU タ⨨ࡢ SPELEEM ⿦⨨ࢆ⏝࠸ࡓࠋ☢ቨ㟁ὶ㥑ືほᐹ࡟ࡘ࠸࡚ࡣࠊᨺ㟁࡟ࡼࡿヨᩱ◚ቯ࡟ࡼࡗ࡚☢ቨ⛣ືほᐹ࡟ࡲ࡛ࡣ⮳ࡽ࡞࠿ࡗࡓࡀࠊࡑࡢཎᅉࡣほᐹ⣲Ꮚࡢ㏆ഐ࡟⤯⦕యࡢ㡿ᇦࡀᗈ࠸ࡓࡵ࡛࠶ࡿࡇ࡜ࢆ✺ࡁṆࡵࡓࠋࡇࢀࡽࡢᐇ㦂⤖ᯝࢆ཯ᫎࡋࠊ2011B ᮇ࡟࠾࠸࡚ࡣSi ᇶᯈࡢ㟢ฟ㠃✚ࢆ࡞ࡿ࡭ࡃᑠࡉࡃࡋࠊ࡞࠾࠿ࡘ Co/Ni ⣽⥺㏆ഐࡢ➃Ꮚࢆࢥࣉࣞࢼ࣮ᵓ㐀࡟ࡋࡓ᪂ࡋ࠸⣲Ꮚ᳨࡛ウࢆ㐍ࡵࡿࠋ࣮࣮࢟࣡ࢻ㸸 SPELEEMࠊᆶ┤☢Ẽ␗᪉ᛶࠊ☢ቨ㟁ὶ㥑ືࠊࡑࡢሙほᐹ⫼ᬒ࡜◊✲┠ⓗ㸸☢ቨࢆᙧᡂࡋࡓ☢ᛶ⣽⥺࡟㟁ὶࢆ㏻ࡌࡿ࡜ࠊࢫࣆࣥ㟁ὶ࡜ᒁᅾ☢Ẽ࣮࣓ࣔࣥࢺ࡜ࡢ㛫࡛ゅ㐠ື㔞ࡀཷࡅΏࡉࢀ࡚☢໬ࡀᅇ㌿ࡋ☢ቨࡀືࡃࠋࡇࡢ⌧㇟ࡣ☢ቨ㟁ὶ㥑ື࡜࿧ࡤࢀࠊ᪂ࡋ࠸ࢫࣆࣥࢺࣟࢽࢡࢫࡢ◊✲ศ㔝࡜ࡋ࡚ᐇ㦂࣭⌮ㄽࡢഃ㠃࠿ࡽከࡃࡢ⯆࿡ࡀᣢࡓࢀ࡚࠸ࡿࠋࡇࢀࡲ࡛࡟☢ቨ⛣ື࣓࢝ࢽࢬ࣒[1-13]ࡸࢹࣂ࢖ࢫᛂ⏝[14-17]࡞࡝ࡢ◊✲ࡀᖜᗈࡃ㐍ࡵࡽࢀࠊከࡃࡢ᪂ࡋ࠸▱ぢࡀᚓࡽࢀ࡚࠸ࡿࠋࢧࣈ࣑ࢡࣟࣥ⣽⥺୰࡟ᙧᡂࡋࡓ☢ቨࡀ⮫⏺㟁ὶᐦᗘ JC ௨ୖ࡛⛣ືࢆࡣࡌࡵࠊࡑࡢ㏿ᗘࡣ㟁ὶᐦᗘ࡟ẚ౛ࡍࡿࡇ࡜ࡀᐇ㦂ⓗ࡟♧ࡉࢀ࡚࠸ࡿ[13]ࠋࡇࡢ≉ᚩࡣࠊ⣲Ꮚࡢᚤ⣽໬࡟ࡼࡾ☢ቨࡀప㟁ὶ࡛㧗㏿࡟⛣ືࡍࡿࡇ࡜ࢆ࠶ࡽࢃࡋࠊ࣓ࣔࣜ㐺⏝࡬ࡢྍ⬟ᛶࢆ♧ࡋ࡚࠸ࡿࠋࡇ࠺ࡋࡓほⅬ࡟❧ࡕࠊᡃࠎࡣ☢ቨ㟁ὶ㥑ື⌧㇟ࡢ࣓ࣔࣜᛂ⏝࡟ࡴࡅࡓ◊✲ࢆ㐍ࡵ࡚࠸ࡿࠋࡇࢀࡲ࡛࡟ࠊ☢ᛶ⣽⥺ࡢ୧➃࡟᥋⥆ࡋࡓ஧ࡘࡢࢺࣛࣥࢪࢫࢱ࠿ࡽࡢ㟁ὶ࡛⣽⥺୰ࡢ☢ቨࢆື࠿ࡍ᭩ࡁ㎸ࡳ᪉ᘧࡢ࣓ࣔࣜࢆᥦ᱌ࡋ
[14-16]ࠊCo/Ni ᆶ┤☢໬⣽⥺࡟ࡼࡿ☢ቨ㟁ὶ㥑ືࢆ᳨ドࡋࡓ[18,19]ࠋࡲࡓࠊᶍᘧⓗ࡞ࢹࣂ࢖ࢫࢆస〇ࡋ࡚ప㟁ຊࠊ㧗㏿ MRAM ࡢྍ⬟ᛶࢆ♧ࡋ࡚࠸ࡿ[10-16]ࠋࡇࢀ࡜ేࡏ࡚ࠊSPring-8ࠊBL17SU タ⨨ࡢ SPELEEM 㻔Spectroscopic Photo Emission and Low Energy Electron Microscope㻕ࢆ⏝࠸࡚ Co/Ni ᆶ┤☢໬⣽⥺ࡢ☢༊ほᐹࢆ࠾ࡇ࡞࠸ࠊ☢ቨ㟁ὶ㥑ື࣓࢝ࢽࢬ࣒ࡢ◊✲ࢆ㐍ࡵ࡚࠸ࡿ[20]ࠋ
2010B ᮇ࡟ࡣࠊ」ᩘࡢ☢ᛶ⣽⥺⣲Ꮚࢆྠ୍᮲௳࡛స〇ࡋࠊྠ୍᮲௳࡛㟁ὶࣃࣝࢫࢆ୚࠼ࡓ࡜ࡁࡢ☢ቨ⛣ື㏿ᗘࢆ⤫ィⓗ࡟ㄪ࡭ࠊ☢ቨ⛣ືࡢᖹᆒ㏿ᗘ࡜ࡑࡢࡤࡽࡘࡁࢆゎᯒࡋࡓࠋྠ୍ᇶᯈୖ࡟స〇ࡋࡓ 5-6 ಶࡢ Co/Ni ᆶ┤☢໬⣽⥺⣲Ꮚ࡟☢ቨᑟධࡋࠊ㟁ὶᐦᗘࢆ J=2.01012 A/m2ࠊ㟁ὶࣃࣝ
ࢫࢆձ10 ns1,3,6 ᅇࡢ」ᩘᅇࠊղ10ࠊ30ࠊ60 ns ࡢ୍ᅇ༳ຍࡋ࡚ࡑࡢᚋࡢ☢ቨ⛣ື㔞ࢆほᐹࡋࡓࠋձࡢ」ᩘᅇࣃࣝࢫ༳ຍࢆࡋࡓ⣲Ꮚ࡛ࡣ☢ቨ⛣ື㏿ᗘࡀ⣙ 35 m/sࠊࡤࡽࡘࡁࡣ⣙ 20 㸣࡛࠶ࡾࠊ㟁Ẽ≉ᛶホ౯ࡢ⤖ᯝ࡜ᑐᛂࡋࡓ[20]ࠋ୍᪉ࠊղࡢ༢୍ࡢ㛗࠸ࣃࣝࢫ࡛୚࠼ࡓሙྜࠊ☢ቨ⛣ື㏿ᗘࡣࣃࣝࢫ㛗࡜࡜ࡶ࡟ῶᑡࡋࠊከ☢༊ᵓ㐀ࡶࡳࡽࢀࡓࠋᏳᐃࡋࡓ☢ቨ⛣ືࡢࡓࡵ࡟ࡣ᪼ ࢆᢚไࡍࡿ▷ࣃࣝࢫ༳ຍࡀ᭷ຠ࡛࠶ࡿࡇ࡜ࡀࢃ࠿ࡗࡓࠋୖグࡢࡼ࠺࡟ࠊྠ୍ᙧ≧⣲Ꮚ࡟࠾ࡅࡿ☢ቨ㏿ᗘࡢࠗ⣲Ꮚ㛫ࡤࡽࡘࡁ࠘࡟࠾࠸࡚ࡣ᳨ドࡀྍ⬟࡟࡞ࡗࡓࡀࠊࢹࣂ࢖ࢫᛂ⏝ࡢࡓࡵ࡟ࡣྠ୍⣲Ꮚෆ࡟࠾ࡅࡿ
☢ቨ㏿ᗘࡢࠗ⮬ᕫࡤࡽࡘࡁ࠘ࡢᣲືࢆ᫂ࡽ࠿࡟ࡍࡿࡇ࡜ࡀᚲ㡲࡛࠶ࡿ࡜⪃࠼ࡽࢀࡿࠋࡑࡇ࡛ᮏㄢ㢟࡛ࡣࠊྠ୍⣲Ꮚ࡟࠾ࡅࡿ☢ቨ⛣ື㏿ᗘ࡜ࡤࡽࡘࡁ࡟ࡘ࠸࡚㆟ㄽࡍࡿࡓࡵ࡟ࠊSPELEEM ⿦⨨ෆ࡟࠾࠸࡚☢ቨᑟධ࠾ࡼࡧ☢ቨ⛣ືࡢࡓࡵࡢ㟁ὶ༳ຍࡀ⾜࠼ࡿࡼ࠺࡞ ᐃ⎔ቃࢆᵓ⠏ࡍࡿࡇ࡜ࢆヨࡳࡓࠋᮏሗ࿌࡛ࡣࠊࡇࢀࡽࡢ᳨ウ⤖ᯝ࡟ࡘ࠸࡚グ㏙ࡍࡿࠋᐇ㦂㸸1. ヨᩱ࡜ᐇ㦂⎔ቃ
Si ᇶᯈୖ࡟ࠊPt㻔1.6nm㻕/[Co㻔0.3nm㻕/Ni㻔0.9nm㻕]4/Co㻔0.3nm㻕/Pt㻔1.6nm㻕/Ta㻔3nm㻕/ᇶᯈ࡞ࡿᵓᡂࡢᆶ┤☢໬⭷ࢆ DC ࣐ࢢࢿࢺࣟࣥࢫࣃࢵࢱἲ㻔MAGEST-T200 ULVAC 〇㻕࡛స〇ࡋࡓࠋࡇࡢ⭷࡟ࣞࢪࢫࢺࢆሬᕸᚋࠊ㟁Ꮚࣅ࣮࣒㟢ග࣭࢖࣑࢜ࣥࣜࣥࢢ࡟ࡼࡾ☢ᛶ⣽⥺ࢆᙧᡂࡋࡓࠋCo/Ni ☢ᛶ⣽⥺ࡢ⥺ᖜࡣ 150 nm ࡛࠶ࡿࠋ☢ᛶ⣽⥺୧➃࡟ࡣࠊ☢
ቨᑟධව㟁ὶὀධ⏝ࡢ Ti/Au ⣽⥺㸦ᖜ 500 nm㸧࡜㟁ὶὀධ⏝ࡢ pad≧ Au 㟁ᴟࢆࣜࣇࢺ࢜ࣇἲ࡛ᙧᡂࡋࡓࠋస〇ࡉࢀࡓ⣲Ꮚࡢᴫᛕᅗ࡜
ගᏛ㢧ᚤ㙾ほᐹീࢆ Fig. 1 ࡟♧ࡍࠋᮏᐇ㦂࡟࠾࠸࡚ࡣࠊᩘ 10 ns ࣮࢜ࢲ࣮ࡢ▷࠸᪉ᙧἼࣃࣝࢫࢆ⣲Ꮚ࡟༳ຍࡍࡿᚲせࡀ࠶ࡿࠋ࡞ࡿ࡭ࡃྠ㍈ࣛ࢖ࣥࢆ☜ಖࡍࡿࡓࡵ࡟ࠊSPELEEM ⿦⨨ࡢ preparation chamberෆ࡛㟁ὶ༳ຍࢆ⾜࠼ࡿࡼ࠺࡞⎔ቃࢆᵓ⠏ࡋࡓࠋᮏ⎔ቃࢆ⏝࠸ࡿࡇ࡜࡛ࠊCo/Ni ⣽⥺࡟ 10 ns ⛬ᗘࡢ᪉ᙧἼࣃࣝࢫࡀ༳ຍྍ⬟࡜࡞ࡗࡓࠋୖグ⣲Ꮚ࡟⣙ 2 kOe ࡢ☢ሙࢆ㠃┤᪉ྥ࡟༳ຍࡋ࡚⣽⥺ࢆ༢☢༊໬ࡋࡓᚋࠊࡲࡎ Ti/Au 㟁ᴟࡢ୧➃࡟ 10 Vࠊ40 ns ࡢࣃࣝࢫ㟁ᅽࢆ༳ຍࡋࠊࡑ
ࡢ㝿Ⓨ⏕ࡍࡿᒁᡤ☢ሙ࡟ࡼࡾ☢ቨࢆᑟධࡋࡓࠋ
2. ☢༊ほᐹ☢༊ほᐹ࡟ࡣ኱ᆺᨺᑕග᪋タ SPring-8 ࡢ BL17SU㸦⌮໬Ꮫ◊✲ᡤࣅ࣮࣒ࣛ࢖ࣥ㸧࡟タ⨨ࡉࢀ࡚࠸ࡿ ELMITEC ♫〇ࡢ SPELEEM ⿦⨨ࢆ⏝࠸ࡓࠋCo L-III ࣆ࣮ࢡ㸦779eV㸧࡟࠾࠸࡚ྑᅇࡾ೫ගࠊᕥᅇࡾ೫
Fig.1 స〇ࡋࡓヨᩱࡢᴫᛕගࢆ⏝࠸ࡓീࢆ᧜ᙳࡋࠊ⡆౽ࡢࡓࡵྑᅇࡾ೫ගീ࡜ᕥᅇࡾ೫ගീࡢᅗ࡜ගᏛ㢧ᚤ㙾ീẚࢆ࡜ࡿࡇ࡜࡛☢༊ീࢆᚓࡓࠋど㔝ᚄࡣ 20 PmI࡜ࡋࡓࠋ⤖ᯝ㸸Fig. 1 ࡢヨᩱ࡟ࠊᇶᯈᆶ┤᪉ྥ࡟⣙ 2 kOe ࡢእ㒊☢ሙࢆ༳ຍࡋࡓᚋࠊSPELEEM ほᐹࡋࡓ࡜ࡁࡢ
ീࢆ Fig. 2㻔a㻕࡟♧ࡍࠋⓑᩳ⥺࡛そࢃࢀࡓ㒊ศࡣ Ti/Au 㟁ᴟ㒊࡛࠶ࡿࠋCo/Ni ⣽⥺୰ࡢ☢໬ࡣࠊࢥࣥ
ࢺࣛࢫࢺࡀ୍ᵝ࡛࠶ࡿࡇ࡜࠿ࡽྠ୍᪉ྥ࡜࡞ࡗ࡚࠸ࡿࡇ࡜ࡀ☜ㄆ࡛ࡁࡿࠋࡇࡢ≧ែ࠿ࡽࠊTi/Au㟁ᴟ㻔㟁ᴟ B ࠿ࡽ A㻕࡟ 10 V㻔⣙ 90 mA㻕ࠊࣃࣝࢫᖜ 40 ns ࡢࣃࣝࢫ㟁ὶࢆ༳ຍࡋࡓᚋࡢほᐹീࢆ Fig.
2㻔b㻕࡟♧ࡍࠋTi/Au 㟁ᴟ௜㏆࡟Ⓨ⏕ࡋࡓ㟁ὶ☢ሙࡢᙳ㡪࡟ࡼࡗ࡚ࠊ㟁ᴟ࿘㎶㒊ࡢࢥࣥࢺࣛࢫࢺࡀ㯮Ⰽ࠿ࡽⓑⰍ࡟ኚ໬ࡋ࡚࠾ࡾࠊCo/Ni ⣽⥺ෆ࡟☢ቨࡀᑟධࡉࢀ࡚࠸ࡿࡇ࡜ࡀほᐹࡉࢀࡓࠋ☢ቨࡢึᮇ఩⨨ࡣࠊ㟁ᴟ➃࠿ࡽ⣙ 400 nm ࡛࠶ࡾࠊ2010B ᮇ࡟⾜ࢃࢀࡓ SPELEEM ⿦⨨እ࡟࡚☢ቨᑟධࢆ⾜ࡗࡓ࡜ࡁࡢ⤖ᯝ࡜୍⮴ࡍࡿࠋFig. 2㻔b㻕࡟♧ࡋࡓࡼ࠺࡟ࠊ
Co/Ni ⣽⥺ෆ࡟☢ቨࢆᑟධࡋࡓ≧ែ࠿ࡽ Ti/Au 㟁ᴟ㻔㟁ᴟ C ࠿ࡽ A㻕࡟ࣃࣝࢫ㟁ὶࢆ༳ຍࡋ࡚☢ቨ⛣ືᐇ㦂ࢆヨࡳࡓࡀࠊ⿦⨨ෆࡢᨺ㟁࡟ࡼࡿヨᩱ◚ቯࡀ㉳ Fig.2 ࣃࣝࢫ㟁ὶ༳ຍ࡟ࡼࡿ☢ቨᑟධ๓ᚋࡢ SPELEEM ほᐹീࡇࡾࠊ☢ቨ⛣ືほᐹࢆ⾜࠺ࡲ࡛࡟ࡣ⮳㻔a㻕༢☢༊≧ែࠊࡽ࡞࠿ࡗࡓࠋヨᩱ◚ቯࡢ୺࡞ཎᅉࡣࠊ(b)☢ቨᑟධᚋ(I~90 mA, t=40 ns ᪉ᙧἼࣃࣝࢫ༳ຍᚋ)ほᐹ⣲Ꮚࡢ㏆ഐ࡟⤯⦕యࡢ㡿ᇦࡀᗈࡃࠊ㟁⏺㞟୰ࡀ㉳ࡇࡗࡓࡇ࡜ࡀ୺࡞ཎᅉ࡜ࡋ࡚⪃࠼ࡽࢀࡿࠋࡇࢀࡽࡢᐇ㦂⤖ᯝࢆ཯ᫎࡋࠊ2011B ᮇ࡟࠾࠸࡚ࡣ Si ᇶᯈࡢ㟢ฟ㠃✚ࢆ࡞ࡿ࡭ࡃᑠࡉࡃࡋࠊࡉࡽ࡟ Co/Ni ⣽⥺㏆ഐࡢ➃Ꮚࢆࢥࣉࣞࢼ࣮ᵓ㐀࡟ࡋࡓ᪂ࡋ࠸⣲Ꮚ᳨࡛ウࢆ㐍ࡵࡿࠋ
ㅰ㎡㸸
SPELEEM ほᐹ࡟༠ຊ࠸ࡓࡔࡁࠊ᭷ព⩏࡞㆟ㄽࢆࡋ࡚࠸ࡓࡔ࠸ࡓ SPring-8 ᮌୗ㇏ᙪẶ࡟ឤㅰ࠸ࡓࡋࡲࡍࠋࡲࡓᡂ⭷࡟ࡣ NEC ஬༑ᔒᛅ஧Ặ࡟ࡈ༠ຊࢆᚓࡲࡋࡓࠋࡇࡇ࡟ឤㅰ࠸ࡓࡋࡲࡍࠋཧ⪃ᩥ⊩㸸
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