Magnetic structures in cross-shaped nano permalloy pattern-arrays embedded in silicon substratesK.Sato, T.Tezuka, T. Yamamoto, K.Machida, T. Ishibashi, Y. Morishita and A. Koukitu2003.10.29

IntroductionVSM, MFM150nm100nm300nm100nm1000nmMFM

Clean Room LaboratoryElectron beam lithography

EB-patterning processDot sizesquare(1m 1m)rectangular(300nm100nm)circular(100 nm)cross(200nm3m, 100nm 1.5m) Patterned area: 3mm3mm4mm4mmEB-resist thickness: 300 nmby spin-coating with 5000 rpm rotationBaking16020minSpin coating of resistEB exposureSi substrateDevelopment

Dry-etching

Etching gas:CF4Vacuum3.010-3PaGas pressure 9.2PaRF power:400WEtching rate: 0.1m/minSilicon surface after etchingDry etching process

LaboratoryEB depositionRF magnetron sputtering

Embedding of permalloyEmbedding of permalloy film by electron beam depositionmaterial:permalloyNi80Fe20Vacuum3.010-6TorrAccelerating voltage 4kV Deposition rate 1.0/secPolishing chemicals: Polished by Kent3(Nanofactor)SlurryGRANZOX sp-15(Al2O3 powder)grain-size20nmpH11polishing rate:60nm/minflatteningChemical mechanical polishing (CMP)

Observation/MFMFE-SEM

SEM observation 300nm100nmsquare dot, 300 nm space

Cross sectional SEM observation

1m square dot arrayAFMMFM

VSM measurement

LLG simulationBy K. Machida

Hy = 10 kOe 0 Oe Dot modeldivMdivMy

Saturation magnetization (Ms)800 emu/cm3Exchange field (A)110-6 erg/cm3Anisotropic constant (Ku)1000 erg/cm3Gyro magnetic constant)-1.76107 rad/(sOe)Damping constant0.2Easy axisY directionDot Size200 nm200 nm100 nmNumber of dot1Mesh size10 nm10 nm10 nm

Hy = 10 kOeHy = 5 kOeHy = 3 kOeHy = 2 kOeHy = 1 kOeHy = 0 Oe

AFM observationCircular dotsRectangular dotsAFM Line scan Surface roughness~10nm

Rectangular dots VSM measurement

Pattern variations for different scan directionScanning directionMFM images

MFM image of 300nm x 100nm dot with a low-moment probe tipAFMMFM

L=3m, d=200nm s=3mL=1.5 m, d=100nm s=1.5 mLds

AFMMFMCROSS3 (200nm3000nm cross dots)

Initial stateProbe-sampleAntiparallel 20kOeprobe-sampleParallel 20kOenmnm cross dots(wide scan)

Initial stateProbe-sampleParallel 20kOeProbe-sample Parallel 20kOe200nm3000nm cross dots(narrow scan)

MFM and AFM images of CROSS3

Kerr microscope image

InitializedProbe-sampleParallel 20kOeProbe-sample Antiparallel 20kOe100nm1500nm cross dots(wide scan)

InitialProbe-sampleParallel 20kOeProbe-sampleParallel 20kOenmnm cross dots(narrow scan)

LLG simulationCross-pattern model Hz = 20 kOe 0 Oe divMdivMz

Hz = 1 kOeHz = 0 OeHz = 5 kOeHz = 10 kOeHz = 20 kOe

Cross1(empty dots)1.5cmcamerascreen30

Cross1(permalloy embedded)30

90Cross3 (permalloy embedded)30

Cross, no magnetic material embedded, H=0PinPoutSinPoutPinSoutSinSout

Cross, permalloy embeddedH=2kOe appliedPinPout1st2nd3rdRepeated measurement

Summary1mLLGMFMLLG

Summary contdKerrSHGSHGMSHG

ProposalMFMLLG1mMO-SNOMMO200nm100nm

AcknowledgementCOE