The switching behavior of magnetic patterns prepared by ion  irradiation was investigated. Co/Pt multilayers with perpendicular anisotropy  and large out-of-plane coercivities 5-6 kOe were grown on electron transparent  SiN windows. Regularly spaced 1 micron sized regions, were magnetically  pattered via ion beam irradiation through a stencil mask. Lorentz TEM was used  to observe in-situ magnetization reversal processes of irradiated regions  under well-defined applied magnetic fields. When the in-plane field was  increased, domain wall motion was observed, resulting in the alignment of the  patterns with the direction of the applied field. The switching mechanism of  the in-plane patterns was by domain wall motion

Baglin, J.E.E.

Folks, L.

Kellock, A.J.

Krishnan, K.M.

Kusinski, G.J.

Terris, B.D.

Thomas, G.

Weller, D.

eScholarship - University of California

Lawrence Berkeley National LaboratoryLawrence Berkeley National LaboratoryTitleLorentz transmission electron microscopy investigation of magnetically patterned Co/Pt multilayersPermalinkhttps://escholarship.org/uc/item/6gr7d3t3AuthorsKusinski, G.J.Krishnan, K.M.Weller, D.et al.Publication Date2000-08-01eScholarship.org Powered by the California Digital LibraryUniversity of CaliforniaPage 1/5LORENTZ TRANSMISSION ELECTRON MICROSCOPY INVESTIGATIONOF MAGNETICALLY PATTERNED Co/Pt MULTILAYERSG.J. KUSINSKI1,2, K.M. KRISHNAN2, D. WELLER3, B.D. TERRIS3,L. FOLKS3, A.J. KELLOCK3, J.E.E. BAGLIN3 AND G. THOMAS1,21) Department of Materials Science and Engineering, University ofCalifornia, Berkeley, CA 94720,2) Materials Sciences Division, Lawrence Berkeley National Laboratory,University of California, Berkeley, CA 94720,3) IBM Almaden Research Center, 650 Harry Road, San Jose, CA 95120AbstractThe switching behavior of magnetic patterns prepared by ion irradiation wasinvestigated.  Co/Pt multilayers with perpendicular anisotropy and large out-of-planecoercivities 5-6 kOe were grown on electron transparent SiN windows.  Regularlyspaced 1 micron sized regions, were magnetically pattered via ion beam irradiationthrough a stencil mask.  Lorentz TEM was used to observe in-situ magnetizationreversal processes of irradiated regions under well-defined applied magnetic fields.When the in-plane field was increased, domain wall motion was observed, resulting inthe alignment of the patterns with the direction of the applied field.  The switchingmechanism of the in-plane patterns was by domain wall motion.1. IntroductionOne of the approaches to ultrahigh-density magnetic storage is patterned magneticmedia.  Previously, small isolated islands of magnetic material have been produced by anumber of techniques [1], all of which require a resist step and subsequent deposition oretch step.  However, with the head-to-disk spacing in the range of 10nm, the cleanlinessof the media surfaces is a key parameter.  For this reason, it is desirable to develop anon-contact magnetic patterning method that preserves surface smoothness andplanarity.  Ion-beam patterning of magnetic thin films through suitable non-contactstencil masks, has been suggested [2] as a good candidate to produce such a planarpatterned media.  Co/Pt multilayers, in particular, are ideally suited for this application,since bombardment with a suitable dose of energetic ions has been shown to change themagnetic easy axis of the multilayer [3].  The irradiation may induce interface mixing[4,5], thereby triggering a spin-reorientation transition from the out-of-plane to the in-plane easy axis.  In addition, ion-irradiation through a resist layer [6], particularlythrough non-contact stencil masks [7], were shown to produce a patterned magneticfilm.  Understanding the switching mechanism of sub-micron magnetic elements is anessential step for the implementation of such patterned media into data storage, and thisis discussed in this paper.Page 2/52. ExperimentalThe samples under study were Co/Pt multilayers deposited by electron beamevaporation.  The Co/Pt multilayer structure consisted of a 20nm Pt buffer layer, 10periods of 3Å Co/10Å Pt, followed by a 10Å Pt capping layer.  Samples were grown onelectron transparent Si3N4windows to facilitate transmission electron microscopy(TEM) and, in particular, the Lorentz magnetic imaging. Magnetic measurements of theas-grown samples were performed using polar and transverse Kerr hysteresismeasurements.As mentioned before, ion-irradiation was found to cause a rotation of the easy axisof the Co/Pt multilayers to in-plane.  The origin of such spin-reorientation (SR) inducedby ion-irradiation is currently investigated by HRTEM but will not be discussed here.The ion induced SR was used to locally change the magnetization of the multilayer.Regularly spaced 1 micron sized regions were patterned via ion beam irradiationthrough a stencil mask with 1micron sized circular holes.  The mask was placed directlyon the film and the sample was bombarded with 700 keV N+ ions from a NEC 3UHPelletron accelerator.  The detailed description of this experiment is describedelsewhere [7].Lorentz transmission electron microscopy was used to investigate the magneticstructure of these patterns.  The objective lens of the microscope is a source of verticalfield, which can be controlled by adjusting the objective lens current [8].  In-situmagnetizing experiments were performed by applying a constant 1500 Oe vertical field.By tilting the sample up to ±35o, an in-plane component of the field, perpendicular tothe specimen tilt axis, can be applied.  Sample was taken through the hysteresis loop,and the Lorentz Fresnel imaging was used to in-situ record the magnetization reversalprocesses of the patterned areas.  In the Fresnel imaging mode contrast arises whenthere is a spatially varying component of the in-plane magnetic induction.  Hence,domain walls appear as dark or bright fringes [9,10].3. Results and DiscussionFigure 1 shows a plan-view, bright field TEM image and an electron diffractionpattern of a Co/Pt multilayer grown at 250oC.  The sample was polycrystalline with anaverage grain size of 50 ± 16nm.  The fine structure visible in some of the grains isattributed to Moiré fringes caused by the small lattice mismatch and rotation betweenCo and Pt planes.  The films have a [111] texture, as indicated by the bright (220) ringin the selected area diffraction pattern (SADP) (see inset Figure 1).  Figure 2 is a TEMcross-section image of the Co/Pt multilayer.  The grain growth is typically columnarwith grains propagating through the film thickness.Figure 3 shows a perpendicular hysteresis loop measured by Kerr rotation.  Thesquareness of the loop indicates that the easy direction of magnetization is out-of-plane.High resolution TEM imaging found the multilayers to have a face centered cubicstacking, what implies a small volume anisotropy of Co.  Hence, the perpendicular easyaxis of magnetization is attributed to the interface anisotropy [5].The deflection of electrons in the TEM is governed by the well-known Lorentzforce,F = -e.(v x B)where e is electron charge, v is the velocity of electrons and B is the magneticinduction.  The deflection β  of electron is given by:Page 3/5β = e.λ.B⊥.t/h,where h is Plank’s constant, λ is the electron wavelength, and B⊥.t is the component ofmagnetic induction perpendicular to the electron path and integrated over thickness t.Therefore, the deflection of the beam is perpendicular to the magnetization.  In the caseof a uniformly magnetized “particle”, this gives an increased intensity, or (seen as)bright fringe, at one end of the patterned region, and decreased intensity, or (seen as)dark fringe at the other end, as schematically illustrated in Figure 4.  Whenmagnetization is reversed the contrast is opposite.Figure 1. Transmission electron micrograph andselected area diffraction pattern of the Co/Ptmultilayer (see text).Figure 2. TEM cross-section image of the Co/Ptmultilayer showing columnar grain growth.  Imageslightly out of focus to enhance the ML’s contrast.Figure 3. Polar Kerr hysteresis loops of a 10x(3ÅCo/10Å Pt) multilayer.  Arrow shows the loop forthe irradiated sample.Figure 4. Schematic illustrating observed Fresnelcontrast for patterned areas. a) side view, b) topview.The analyzed multilayers consist of only 3nm of magnetic thickness, what resultsin a very small magnetic signal contribution to the overall contrast.  This is mainly dueto the strong microstructure contrast, arising from the diffraction of the individualcolumnar grains, as shown in Figure 1.  However, in this case the physicalmicrostructure is on a significantly smaller scale than the magnetic pattern size (50nm-1.5-1-0.500.511.5-15 -5 5 15Magnetic Field [kOe]Polar Kerr Rotation BBrightDarkb)XDark BrightBa)FIntensityFPage 4/5vs. 1µm).  Hence, the influence of the high spatial frequency component (physicalmicrostructure) was reduced by utilizing a large 100µm defocus in the Fresnel mode,which however limits the resolution.Figure 5 shows a series of Fresnel images of the patterned multilayers, recorded atdifferent sample tilts, and hence at a different in-plane magnetic field applied.  For eachimage, the sample tilt and the applied in-plane magnetic field are indicated. Figure 5a isan image recorded at a 10o tilt (H|| = 264 Oe).  This field was sufficient to align all thein-plane patterned areas.  The Fresnel contrast consists of dark and bright fringes at thetop and bottom, respectively, of each irradiated pattern.  The contrast is consistent withthe sample being magnetized to the right, along the applied field direction as indicatedby the arrow and explained in Figure 4.Figure 5. A series of Fresnel images of patterned multilayers recorded at different sample tilts.a) tilt =10o; H| | = 264 Oe, b) tilt = 0.3o; H| | = 7 Oe, c) tilt = -2o; H| | = -54 Oe, d) tilt = -3.1o; H| | = -82 Oe,e) tilt = -5.1o; H| | = -135 Oe, f) tilt = -10o; H| | = -264 Oe.When the in-plane field was decreased, the sample remained magnetized in thesame direction.  Figure 5b, shows the area with the field reduced to H|| = ~7 Oe.Patterned areas still have a white fringe at the bottom but some develop split contrast.When the field was applied in negative direction, reversal was observed by domain wallmotion.  The reversal, for some of the patterns, starts at relatively low fields (Figure 5c,H|| = -54 Oe), however, patterns magnetized in positive direction are still present.  Atthis field for some of the patterns, the contrast changes to a bright (dark) fringe at thetop and at the bottom what corresponds to white, almost continuous, circular fringe anddark center, (dark area with bright middle).  The patterns showing this contrast supportthe multi-domain state, and hence Lorentz deflection is in both directions.  When thefield is further increased in negative direction, (Figure 5d, H|| = -82 Oe), the multi-domain contrast is observed for most of the patterns.   As the field is further increased,Page 5/5(Figure 5e, H|| = -135 Oe), the observed contrast is similar to that in Figure 5d, howevernotice that the bright fringes are less continuous, and are brighter at the top of thepatterns what implies multidomain state with majority of the area already magnetized innegative direction.   Finally, when H|| = -264 Oe is applied further domain wall motionwas observed.  This resulted in the complete alignment of the patterns with the directionof the applied field, (to the left), as shown in Figure 5f.  The Fresnel contrast consistsonly of dark and bright fringes at the bottom and the top, respectively, which is oppositeto the contrast shown on Figure 5a.4. ConclusionsThe analyzed Co/Pt multilayers were polycrystalline [111] textured, with anaverage grain size of 50 ± 16nm.  The switching mechanism of the in-plane patternsprepared by ion irradiation was by domain wall motion.  In the remanent state, and withno field applied, the irradiated areas were in-plane and supported a multi-domainconfiguration.  The significant softening of the in-plane regions (Hc < 300 Oe) ascompared to the out-of-plane coercivity was recorded.AcknowledgementsGreg Kusinski acknowledges financial support through the “IBM ResearchFellowship”.  Work at MSD and NCEM at LBNL was supported by the Director, Officeof Energy Research, Office of Basic Energy Sciences, Materials Sciences Division ofthe U.S. Department of Energy under contract No. DE-AC03-76SF00098References1 Farhoud, M.; Hwang, M.; Smith, Henry I.; Schattenburg, M.L.; Bae, J.M.; Youcef-Toumi, K.; Ross, C.A.(1998)  Fabrication of large area nanostructured magnets by interferometric lithography, IEEE Transactionson Magnetics 34, 1087-1089.Ross, CA; Smith, HI; Savas, T; Schattenburg, M; Farhoud, M; Hwang, M; Walsh, M; Abraham, MC; Ram,RJ.  (1999) Fabrication of patterned media for high density magnetic storage, J. Vac. Sci. Tehcnol. B 17,3168-3176.2 Chappert, C., Bernas, H., Ferré, J., Kottler, V., Jamet, J. -P., Chen, Y., Cambril, E., Devolder, T.,Rousseaux, F., Mathet, V., and Launois, H. (1998) Planar Patterned Magnetic Media Obtained By IonIrradiation, Science 280, 1919-1922.3 Ferré, J., Chappert, C., Bernas, H., Jamet, J.-P., Meyer, P., Kaitasov, O., Lemerle, S., Mathet, V.,Rousseaux, F., and Launois H. (1999) Irradiation Induced Effects on Magnetic Properties of Pt/Co/PtUltrathin Films, J. Magn. Magn. Mater. 191,198-199.4 Carcia, P.F., Shah, S.I., and Zeper, W.B. (1990) Effect of energetic bombardment on the magneticcoercivity of sputtered Pt/Co thin-film multilayers, Appl. Phys. Lett. 56, 2345.5 Weller, D. Baglin, J.E.E., Kellock, A.J., Hannibal, K.A., Toney, M.F., Kusinski, G., Lang, S., Folks, L.,Best M.E., and Terris, B.D. (2000) Ion Induced Magnetization Reorientation in Co/Pt Multilayers forPatterned Media, J. Appl. Phys. 87, 5768-5770.6 Devolder, T., Chappert, C., Chen, Y., Cambril, E., Bernas, H., Jamet, J.-P., and Ferré, J. (1999) Sub 50 nmplanar magnetic nanostructures fabricated by ion irradiation, Appl. Phys. Lett. 74, 3383-3385.7 Terris, B., Folks, L., Weller, D., Baglin, J.E.E., Kellock, A.J., Rothuizen, H., and Vettiger, P. (1999) IonBeam Patterning of Magnetic Films Using Stencil Masks, Appl. Phys. Lett. 75, 403-405.8 Verbist, K., Nelson, E.C., Anthony, T.C., Brug, J.A., and K.M. Krishnan (1998) Lorentz transmissionelectron microscopy in a standard CM200FEG, Proc. Int. Conf. Elec. Mic., ICEM14, vol II, 503-5049 Fuller, H.W., and Hale, M.E. (1959) Determination of magnetization distribution in thin foils using electronmicroscopy, J. Appl. Phys. 31, 238-234.10 Chapman, J.N. (1984) The investigation of magnetic domain structures in thin foils by electronmicroscopy, J. Phys. D: Apply. Phys. 17, 623-647

English

Lorentz transmission electron microscopy investigation of magnetically 
patterned Co/Pt multilayers

The switching behavior of magnetic patterns prepared by ion irradiation was investigated. Co/Pt multilayers with perpendicular anisotropy and large out-of-plane coercivities 5-6 kOe were grown on electron transparent SiN windows. Regularly spaced 1 micron sized regions, were magnetically pattered via ion beam irradiation through a stencil mask. Lorentz TEM was used to observe in-situ magnetization reversal processes of irradiated regions under well-defined applied magnetic fields. When the in-plane field was increased, domain wall motion was observed, resulting in the alignment of the patterns with the direction of the applied field. The switching mechanism of the in-plane patterns was by domain wall motion

Kusinski, G. J.

Krishnan, K. M.

Terris, B. D.

Kellock, A. J.

Baglin, J. E. E.

UNT Digital Library

Page 1/5LORENTZ TRANSMISSION ELECTRON MICROSCOPY INVESTIGATIONOF MAGNETICALLY PATTERNED Co/Pt MULTILAYERSG.J. KUSINSKI1,2, K.M. KRISHNAN2, D. WELLER3, B.D. TERRIS3,L. FOLKS3, A.J. KELLOCK3, J.E.E. BAGLIN3 AND G. THOMAS1,21) Department of Materials Science and Engineering, University ofCalifornia, Berkeley, CA 94720,2) Materials Sciences Division, Lawrence Berkeley National Laboratory,University of California, Berkeley, CA 94720,3) IBM Almaden Research Center, 650 Harry Road, San Jose, CA 95120AbstractThe switching behavior of magnetic patterns prepared by ion irradiation wasinvestigated.  Co/Pt multilayers with perpendicular anisotropy and large out-of-planecoercivities 5-6 kOe were grown on electron transparent SiN windows.  Regularlyspaced 1 micron sized regions, were magnetically pattered via ion beam irradiationthrough a stencil mask.  Lorentz TEM was used to observe in-situ magnetizationreversal processes of irradiated regions under well-defined applied magnetic fields.When the in-plane field was increased, domain wall motion was observed, resulting inthe alignment of the patterns with the direction of the applied field.  The switchingmechanism of the in-plane patterns was by domain wall motion.1. IntroductionOne of the approaches to ultrahigh-density magnetic storage is patterned magneticmedia.  Previously, small isolated islands of magnetic material have been produced by anumber of techniques [1], all of which require a resist step and subsequent deposition oretch step.  However, with the head-to-disk spacing in the range of 10nm, the cleanlinessof the media surfaces is a key parameter.  For this reason, it is desirable to develop anon-contact magnetic patterning method that preserves surface smoothness andplanarity.  Ion-beam patterning of magnetic thin films through suitable non-contactstencil masks, has been suggested [2] as a good candidate to produce such a planarpatterned media.  Co/Pt multilayers, in particular, are ideally suited for this application,since bombardment with a suitable dose of energetic ions has been shown to change themagnetic easy axis of the multilayer [3].  The irradiation may induce interface mixing[4,5], thereby triggering a spin-reorientation transition from the out-of-plane to the in-plane easy axis.  In addition, ion-irradiation through a resist layer [6], particularlythrough non-contact stencil masks [7], were shown to produce a patterned magneticfilm.  Understanding the switching mechanism of sub-micron magnetic elements is anessential step for the implementation of such patterned media into data storage, and thisis discussed in this paper.Page 2/52. ExperimentalThe samples under study were Co/Pt multilayers deposited by electron beamevaporation.  The Co/Pt multilayer structure consisted of a 20nm Pt buffer layer, 10periods of 3Å Co/10Å Pt, followed by a 10Å Pt capping layer.  Samples were grown onelectron transparent Si3N4windows to facilitate transmission electron microscopy(TEM) and, in particular, the Lorentz magnetic imaging. Magnetic measurements of theas-grown samples were performed using polar and transverse Kerr hysteresismeasurements.As mentioned before, ion-irradiation was found to cause a rotation of the easy axisof the Co/Pt multilayers to in-plane.  The origin of such spin-reorientation (SR) inducedby ion-irradiation is currently investigated by HRTEM but will not be discussed here.The ion induced SR was used to locally change the magnetization of the multilayer.Regularly spaced 1 micron sized regions were patterned via ion beam irradiationthrough a stencil mask with 1micron sized circular holes.  The mask was placed directlyon the film and the sample was bombarded with 700 keV N+ ions from a NEC 3UHPelletron accelerator.  The detailed description of this experiment is describedelsewhere [7].Lorentz transmission electron microscopy was used to investigate the magneticstructure of these patterns.  The objective lens of the microscope is a source of verticalfield, which can be controlled by adjusting the objective lens current [8].  In-situmagnetizing experiments were performed by applying a constant 1500 Oe vertical field.By tilting the sample up to ±35o, an in-plane component of the field, perpendicular tothe specimen tilt axis, can be applied.  Sample was taken through the hysteresis loop,and the Lorentz Fresnel imaging was used to in-situ record the magnetization reversalprocesses of the patterned areas.  In the Fresnel imaging mode contrast arises whenthere is a spatially varying component of the in-plane magnetic induction.  Hence,domain walls appear as dark or bright fringes [9,10].3. Results and DiscussionFigure 1 shows a plan-view, bright field TEM image and an electron diffractionpattern of a Co/Pt multilayer grown at 250oC.  The sample was polycrystalline with anaverage grain size of 50 ± 16nm.  The fine structure visible in some of the grains isattributed to Moiré fringes caused by the small lattice mismatch and rotation betweenCo and Pt planes.  The films have a [111] texture, as indicated by the bright (220) ringin the selected area diffraction pattern (SADP) (see inset Figure 1).  Figure 2 is a TEMcross-section image of the Co/Pt multilayer.  The grain growth is typically columnarwith grains propagating through the film thickness.Figure 3 shows a perpendicular hysteresis loop measured by Kerr rotation.  Thesquareness of the loop indicates that the easy direction of magnetization is out-of-plane.High resolution TEM imaging found the multilayers to have a face centered cubicstacking, what implies a small volume anisotropy of Co.  Hence, the perpendicular easyaxis of magnetization is attributed to the interface anisotropy [5].The deflection of electrons in the TEM is governed by the well-known Lorentzforce,F = -e.(v x B)where e is electron charge, v is the velocity of electrons and B is the magneticinduction.  The deflection β  of electron is given by:Page 3/5β = e.λ.B⊥.t/h,where h is Plank’s constant, λ is the electron wavelength, and B⊥.t is the component ofmagnetic induction perpendicular to the electron path and integrated over thickness t.Therefore, the deflection of the beam is perpendicular to the magnetization.  In the caseof a uniformly magnetized “particle”, this gives an increased intensity, or (seen as)bright fringe, at one end of the patterned region, and decreased intensity, or (seen as)dark fringe at the other end, as schematically illustrated in Figure 4.  Whenmagnetization is reversed the contrast is opposite.Figure 1. Transmission electron micrograph andselected area diffraction pattern of the Co/Ptmultilayer (see text).Figure 2. TEM cross-section image of the Co/Ptmultilayer showing columnar grain growth.  Imageslightly out of focus to enhance the ML’s contrast.Figure 3. Polar Kerr hysteresis loops of a 10x(3ÅCo/10Å Pt) multilayer.  Arrow shows the loop forthe irradiated sample.Figure 4. Schematic illustrating observed Fresnelcontrast for patterned areas. a) side view, b) topview.The analyzed multilayers consist of only 3nm of magnetic thickness, what resultsin a very small magnetic signal contribution to the overall contrast.  This is mainly dueto the strong microstructure contrast, arising from the diffraction of the individualcolumnar grains, as shown in Figure 1.  However, in this case the physicalmicrostructure is on a significantly smaller scale than the magnetic pattern size (50nm-1.5-1-0.500.511.5-15 -5 5 15Magnetic Field [kOe]Polar Kerr Rotation BBrightDarkb)XDark BrightBa)FIntensityFPage 4/5vs. 1µm).  Hence, the influence of the high spatial frequency component (physicalmicrostructure) was reduced by utilizing a large 100µm defocus in the Fresnel mode,which however limits the resolution.Figure 5 shows a series of Fresnel images of the patterned multilayers, recorded atdifferent sample tilts, and hence at a different in-plane magnetic field applied.  For eachimage, the sample tilt and the applied in-plane magnetic field are indicated. Figure 5a isan image recorded at a 10o tilt (H|| = 264 Oe).  This field was sufficient to align all thein-plane patterned areas.  The Fresnel contrast consists of dark and bright fringes at thetop and bottom, respectively, of each irradiated pattern.  The contrast is consistent withthe sample being magnetized to the right, along the applied field direction as indicatedby the arrow and explained in Figure 4.Figure 5. A series of Fresnel images of patterned multilayers recorded at different sample tilts.a) tilt =10o; H| | = 264 Oe, b) tilt = 0.3o; H| | = 7 Oe, c) tilt = -2o; H| | = -54 Oe, d) tilt = -3.1o; H| | = -82 Oe,e) tilt = -5.1o; H| | = -135 Oe, f) tilt = -10o; H| | = -264 Oe.When the in-plane field was decreased, the sample remained magnetized in thesame direction.  Figure 5b, shows the area with the field reduced to H|| = ~7 Oe.Patterned areas still have a white fringe at the bottom but some develop split contrast.When the field was applied in negative direction, reversal was observed by domain wallmotion.  The reversal, for some of the patterns, starts at relatively low fields (Figure 5c,H|| = -54 Oe), however, patterns magnetized in positive direction are still present.  Atthis field for some of the patterns, the contrast changes to a bright (dark) fringe at thetop and at the bottom what corresponds to white, almost continuous, circular fringe anddark center, (dark area with bright middle).  The patterns showing this contrast supportthe multi-domain state, and hence Lorentz deflection is in both directions.  When thefield is further increased in negative direction, (Figure 5d, H|| = -82 Oe), the multi-domain contrast is observed for most of the patterns.   As the field is further increased,Page 5/5(Figure 5e, H|| = -135 Oe), the observed contrast is similar to that in Figure 5d, howevernotice that the bright fringes are less continuous, and are brighter at the top of thepatterns what implies multidomain state with majority of the area already magnetized innegative direction.   Finally, when H|| = -264 Oe is applied further domain wall motionwas observed.  This resulted in the complete alignment of the patterns with the directionof the applied field, (to the left), as shown in Figure 5f.  The Fresnel contrast consistsonly of dark and bright fringes at the bottom and the top, respectively, which is oppositeto the contrast shown on Figure 5a.4. ConclusionsThe analyzed Co/Pt multilayers were polycrystalline [111] textured, with anaverage grain size of 50 ± 16nm.  The switching mechanism of the in-plane patternsprepared by ion irradiation was by domain wall motion.  In the remanent state, and withno field applied, the irradiated areas were in-plane and supported a multi-domainconfiguration.  The significant softening of the in-plane regions (Hc < 300 Oe) ascompared to the out-of-plane coercivity was recorded.AcknowledgementsGreg Kusinski acknowledges financial support through the “IBM ResearchFellowship”.  Work at MSD and NCEM at LBNL was supported by the Director, Officeof Energy Research, Office of Basic Energy Sciences, Materials Sciences Division ofthe U.S. Department of Energy under contract No. DE-AC03-76SF00098References1 Farhoud, M.; Hwang, M.; Smith, Henry I.; Schattenburg, M.L.; Bae, J.M.; Youcef-Toumi, K.; Ross, C.A.(1998)  Fabrication of large area nanostructured magnets by interferometric lithography, IEEE Transactionson Magnetics 34, 1087-1089.Ross, CA; Smith, HI; Savas, T; Schattenburg, M; Farhoud, M; Hwang, M; Walsh, M; Abraham, MC; Ram,RJ.  (1999) Fabrication of patterned media for high density magnetic storage, J. Vac. Sci. Tehcnol. B 17,3168-3176.2 Chappert, C., Bernas, H., Ferré, J., Kottler, V., Jamet, J. -P., Chen, Y., Cambril, E., Devolder, T.,Rousseaux, F., Mathet, V., and Launois, H. (1998) Planar Patterned Magnetic Media Obtained By IonIrradiation, Science 280, 1919-1922.3 Ferré, J., Chappert, C., Bernas, H., Jamet, J.-P., Meyer, P., Kaitasov, O., Lemerle, S., Mathet, V.,Rousseaux, F., and Launois H. (1999) Irradiation Induced Effects on Magnetic Properties of Pt/Co/PtUltrathin Films, J. Magn. Magn. Mater. 191,198-199.4 Carcia, P.F., Shah, S.I., and Zeper, W.B. (1990) Effect of energetic bombardment on the magneticcoercivity of sputtered Pt/Co thin-film multilayers, Appl. Phys. Lett. 56, 2345.5 Weller, D. Baglin, J.E.E., Kellock, A.J., Hannibal, K.A., Toney, M.F., Kusinski, G., Lang, S., Folks, L.,Best M.E., and Terris, B.D. (2000) Ion Induced Magnetization Reorientation in Co/Pt Multilayers forPatterned Media, J. Appl. Phys. 87, 5768-5770.6 Devolder, T., Chappert, C., Chen, Y., Cambril, E., Bernas, H., Jamet, J.-P., and Ferré, J. (1999) Sub 50 nmplanar magnetic nanostructures fabricated by ion irradiation, Appl. Phys. Lett. 74, 3383-3385.7 Terris, B., Folks, L., Weller, D., Baglin, J.E.E., Kellock, A.J., Rothuizen, H., and Vettiger, P. (1999) IonBeam Patterning of Magnetic Films Using Stencil Masks, Appl. Phys. Lett. 75, 403-405.8 Verbist, K., Nelson, E.C., Anthony, T.C., Brug, J.A., and K.M. Krishnan (1998) Lorentz transmissionelectron microscopy in a standard CM200FEG, Proc. Int. Conf. Elec. Mic., ICEM14, vol II, 503-5049 Fuller, H.W., and Hale, M.E. (1959) Determination of magnetization distribution in thin foils using electronmicroscopy, J. Appl. Phys. 31, 238-234.10 Chapman, J.N. (1984) The investigation of magnetic domain structures in thin foils by electronmicroscopy, J. Phys. D: Apply. Phys. 17, 623-647

Lorentz transmission electron microscopy investigation of magnetically patterned Co/Pt multilayers

Lorentz transmission electron microscopy investigation of magnetically patterned Co/Pt multilayers

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