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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.


Related in: MedlinePlus

Magnetic analysis on the magnetic patterned Co/Pt MLs.(a) ac-demagnetized MFM images of the uncapped (upper row) and the Ag-capped samples (lower row) at the as-deposited state, and after 250 oC, and 350 oC RTA. (b) ΔM curves with different Tann and capping conditions. (c) Tann dependence of the ac-demagnetized domain size (Ddomain) and activation volume (Vact). (d) Dependence between Ddomain and Vact. (e) Correlation between the reciprocal of activation volume (1/Vact) and nucleation field (Hn) of samples with different Tann. The red and blue arrows indicate the different amount of activation volume change from the as-deposited to the 350 oC annealed for uncapped and Ag-capped cases, respectively.
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f3: Magnetic analysis on the magnetic patterned Co/Pt MLs.(a) ac-demagnetized MFM images of the uncapped (upper row) and the Ag-capped samples (lower row) at the as-deposited state, and after 250 oC, and 350 oC RTA. (b) ΔM curves with different Tann and capping conditions. (c) Tann dependence of the ac-demagnetized domain size (Ddomain) and activation volume (Vact). (d) Dependence between Ddomain and Vact. (e) Correlation between the reciprocal of activation volume (1/Vact) and nucleation field (Hn) of samples with different Tann. The red and blue arrows indicate the different amount of activation volume change from the as-deposited to the 350 oC annealed for uncapped and Ag-capped cases, respectively.

Mentions: In addition to the changes of Hn and Hp, we also observed that sizes of the ac-demagnetized domains (Ddomain) are shrunk by elevating Tann, as shown in Fig. 3(a). Furthermore, the Ag-capped samples show the less modification of Ddomain compared to the uncapped ones. Based on the micromagnetic simulations reported by R. H. Victora et al.29, with Keff and Ms almost constant, the ac-demagnetized domain size of Co/Pt MLs can be determined by intergranular exchange coupling, which can be evaluated by using the ΔM curves30. In Fig. 3(b), the upper and lower panels show the ΔM curves of the uncapped and the Ag-capped samples, respectively. All samples exhibit positive ΔM peaks, indicating an exchange interaction dominated magnetization reversal31. The higher positive maximum intensity of the ΔM curve (ΔM(H)Max) indicates the stronger intergranular exchange coupling32. For all samples, the intergranular exchange coupling reduces with the elevating Tann as the ΔM(H)Max drops. The Ag-capped samples show a smaller drop of ΔM(H)Max with Tann than that of the uncapped counterparts, implying that the extra Ag capping layer hinders the reduction of intergranular exchange coupling during the RTA process. Furthermore, we also notice that the samples with smaller intergranular exchange coupling (lower ΔM(H)Max and smaller Ddomain) shows higher Hn, indicating that the intergranular exchange coupling should be an important factor for the magnetization reversal of Co/Pt MLs here.


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 analysis on the magnetic patterned Co/Pt MLs.(a) ac-demagnetized MFM images of the uncapped (upper row) and the Ag-capped samples (lower row) at the as-deposited state, and after 250 oC, and 350 oC RTA. (b) ΔM curves with different Tann and capping conditions. (c) Tann dependence of the ac-demagnetized domain size (Ddomain) and activation volume (Vact). (d) Dependence between Ddomain and Vact. (e) Correlation between the reciprocal of activation volume (1/Vact) and nucleation field (Hn) of samples with different Tann. The red and blue arrows indicate the different amount of activation volume change from the as-deposited to the 350 oC annealed for uncapped and Ag-capped cases, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: Magnetic analysis on the magnetic patterned Co/Pt MLs.(a) ac-demagnetized MFM images of the uncapped (upper row) and the Ag-capped samples (lower row) at the as-deposited state, and after 250 oC, and 350 oC RTA. (b) ΔM curves with different Tann and capping conditions. (c) Tann dependence of the ac-demagnetized domain size (Ddomain) and activation volume (Vact). (d) Dependence between Ddomain and Vact. (e) Correlation between the reciprocal of activation volume (1/Vact) and nucleation field (Hn) of samples with different Tann. The red and blue arrows indicate the different amount of activation volume change from the as-deposited to the 350 oC annealed for uncapped and Ag-capped cases, respectively.
Mentions: In addition to the changes of Hn and Hp, we also observed that sizes of the ac-demagnetized domains (Ddomain) are shrunk by elevating Tann, as shown in Fig. 3(a). Furthermore, the Ag-capped samples show the less modification of Ddomain compared to the uncapped ones. Based on the micromagnetic simulations reported by R. H. Victora et al.29, with Keff and Ms almost constant, the ac-demagnetized domain size of Co/Pt MLs can be determined by intergranular exchange coupling, which can be evaluated by using the ΔM curves30. In Fig. 3(b), the upper and lower panels show the ΔM curves of the uncapped and the Ag-capped samples, respectively. All samples exhibit positive ΔM peaks, indicating an exchange interaction dominated magnetization reversal31. The higher positive maximum intensity of the ΔM curve (ΔM(H)Max) indicates the stronger intergranular exchange coupling32. For all samples, the intergranular exchange coupling reduces with the elevating Tann as the ΔM(H)Max drops. The Ag-capped samples show a smaller drop of ΔM(H)Max with Tann than that of the uncapped counterparts, implying that the extra Ag capping layer hinders the reduction of intergranular exchange coupling during the RTA process. Furthermore, we also notice that the samples with smaller intergranular exchange coupling (lower ΔM(H)Max and smaller Ddomain) shows higher Hn, indicating that the intergranular exchange coupling should be an important factor for the magnetization reversal of Co/Pt MLs here.

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.


Related in: MedlinePlus