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Magnetic patterning: local manipulation of the intergranular exchange coupling via grain boundary engineering.

Huang KF, Liao JW, Hsieh CY, Wang LW, Huang YC, Wen WC, Chang MT, Lo SC, Yuan J, Lin HH, Lai CH - Sci Rep (2015)

Bottom Line: As demonstration, the grain boundary structure of Co/Pt multilayers is engineered by thermal treatment, where the stress state of the multilayers and thus the intergranular exchange coupling can be modified.With Ag passivation layers on top of the Co/Pt multilayers, we can hinder the stress relaxation and grain boundary modification.Combining the pre-patterned Ag passivation layer with thermal treatment, we can design spatial variations of the magnetic properties by tuning the intergranular exchange coupling, which diversifies the magnetic patterning process and extends its feasibility for varieties of new devices.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, 300, Taiwan.

ABSTRACT
Magnetic patterning, with designed spatial profile of the desired magnetic properties, has been a rising challenge for developing magnetic devices at nanoscale. Most existing methods rely on locally modifying magnetic anisotropy energy or saturation magnetization, and thus post stringent constraints on the adaptability in diverse applications. We propose an alternative route for magnetic patterning: by manipulating the local intergranular exchange coupling to tune lateral magnetic properties. As demonstration, the grain boundary structure of Co/Pt multilayers is engineered by thermal treatment, where the stress state of the multilayers and thus the intergranular exchange coupling can be modified. With Ag passivation layers on top of the Co/Pt multilayers, we can hinder the stress relaxation and grain boundary modification. Combining the pre-patterned Ag passivation layer with thermal treatment, we can design spatial variations of the magnetic properties by tuning the intergranular exchange coupling, which diversifies the magnetic patterning process and extends its feasibility for varieties of new devices.

No MeSH data available.


Magnetic patterning by Joule heating (a) A sketch of the process flow for Joule heating annealing, where individual wire can be selected for magnetic patterning. (b) Hysteresis loops obtained by FMOKE at different regions on the magnetic patterned wire. The insertion of (b) shows the MFM image of magnetic patterned magnetic wire at the partially saturated states. The Ag-capped region is indicated by blue dot-squares with different width of Ag pre-pattern (4 and 2 μm, respectively).
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f5: Magnetic patterning by Joule heating (a) A sketch of the process flow for Joule heating annealing, where individual wire can be selected for magnetic patterning. (b) Hysteresis loops obtained by FMOKE at different regions on the magnetic patterned wire. The insertion of (b) shows the MFM image of magnetic patterned magnetic wire at the partially saturated states. The Ag-capped region is indicated by blue dot-squares with different width of Ag pre-pattern (4 and 2 μm, respectively).

Mentions: As discussed in previous paragraphs, the magnetic properties can be locally manipulated by controlling stress relaxation during annealing process. However, the infared lamp used in our RTA process, providing uniform heating area for the whole sample, should not be the only driving force for stress relaxation. Here we demonstrate how Joule heating48 generated by currents can replace the RTA process so that we can selectively anneal the designated magnetic wires. The Joule heating method provides another route to manipulate the spatial distribution of magnetic properties. As shown in Fig. 5(a), by applying current pulses (40 pulses with the current density of 45MA/cm2 and the duration of 50 ms for each pulse) into the selected magnetic wires, only the wires with current are annealed. The same passivation effects as RTA are observed by using Joule heating annealing. As shown in Fig. 5(b), the hysteresis loops acquired by FMOKE reveal that the magnetization switching of the Ag-capped regions occurs at a lower field than that of the uncapped regions. Inset of Fig. 5(b) shows the partially reversed MFM images of the magnetic patterned Co/Pt MLs wires by Joule heating annealing. Indeed, the reversed domain first nucleated in Ag-capped regions (enclosed by blue dot-squares) and the domain walls was pinned at the boundary between the Ag-capped and uncapped regions, that is, the magnetic patterning can be achieved not only by RTA but by Joule heating annealing.


Magnetic patterning: local manipulation of the intergranular exchange coupling via grain boundary engineering.

Huang KF, Liao JW, Hsieh CY, Wang LW, Huang YC, Wen WC, Chang MT, Lo SC, Yuan J, Lin HH, Lai CH - Sci Rep (2015)

Magnetic patterning by Joule heating (a) A sketch of the process flow for Joule heating annealing, where individual wire can be selected for magnetic patterning. (b) Hysteresis loops obtained by FMOKE at different regions on the magnetic patterned wire. The insertion of (b) shows the MFM image of magnetic patterned magnetic wire at the partially saturated states. The Ag-capped region is indicated by blue dot-squares with different width of Ag pre-pattern (4 and 2 μm, respectively).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4496669&req=5

f5: Magnetic patterning by Joule heating (a) A sketch of the process flow for Joule heating annealing, where individual wire can be selected for magnetic patterning. (b) Hysteresis loops obtained by FMOKE at different regions on the magnetic patterned wire. The insertion of (b) shows the MFM image of magnetic patterned magnetic wire at the partially saturated states. The Ag-capped region is indicated by blue dot-squares with different width of Ag pre-pattern (4 and 2 μm, respectively).
Mentions: As discussed in previous paragraphs, the magnetic properties can be locally manipulated by controlling stress relaxation during annealing process. However, the infared lamp used in our RTA process, providing uniform heating area for the whole sample, should not be the only driving force for stress relaxation. Here we demonstrate how Joule heating48 generated by currents can replace the RTA process so that we can selectively anneal the designated magnetic wires. The Joule heating method provides another route to manipulate the spatial distribution of magnetic properties. As shown in Fig. 5(a), by applying current pulses (40 pulses with the current density of 45MA/cm2 and the duration of 50 ms for each pulse) into the selected magnetic wires, only the wires with current are annealed. The same passivation effects as RTA are observed by using Joule heating annealing. As shown in Fig. 5(b), the hysteresis loops acquired by FMOKE reveal that the magnetization switching of the Ag-capped regions occurs at a lower field than that of the uncapped regions. Inset of Fig. 5(b) shows the partially reversed MFM images of the magnetic patterned Co/Pt MLs wires by Joule heating annealing. Indeed, the reversed domain first nucleated in Ag-capped regions (enclosed by blue dot-squares) and the domain walls was pinned at the boundary between the Ag-capped and uncapped regions, that is, the magnetic patterning can be achieved not only by RTA but by Joule heating annealing.

Bottom Line: As demonstration, the grain boundary structure of Co/Pt multilayers is engineered by thermal treatment, where the stress state of the multilayers and thus the intergranular exchange coupling can be modified.With Ag passivation layers on top of the Co/Pt multilayers, we can hinder the stress relaxation and grain boundary modification.Combining the pre-patterned Ag passivation layer with thermal treatment, we can design spatial variations of the magnetic properties by tuning the intergranular exchange coupling, which diversifies the magnetic patterning process and extends its feasibility for varieties of new devices.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, 300, Taiwan.

ABSTRACT
Magnetic patterning, with designed spatial profile of the desired magnetic properties, has been a rising challenge for developing magnetic devices at nanoscale. Most existing methods rely on locally modifying magnetic anisotropy energy or saturation magnetization, and thus post stringent constraints on the adaptability in diverse applications. We propose an alternative route for magnetic patterning: by manipulating the local intergranular exchange coupling to tune lateral magnetic properties. As demonstration, the grain boundary structure of Co/Pt multilayers is engineered by thermal treatment, where the stress state of the multilayers and thus the intergranular exchange coupling can be modified. With Ag passivation layers on top of the Co/Pt multilayers, we can hinder the stress relaxation and grain boundary modification. Combining the pre-patterned Ag passivation layer with thermal treatment, we can design spatial variations of the magnetic properties by tuning the intergranular exchange coupling, which diversifies the magnetic patterning process and extends its feasibility for varieties of new devices.

No MeSH data available.