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Hysteresis loops of individual Co nanostripes measured by magnetic force microscopy.

Jaafar M, Serrano-Ramón L, Iglesias-Freire O, Fernández-Pacheco A, Ibarra MR, De Teresa JM, Asenjo A - Nanoscale Res Lett (2011)

Bottom Line: In the present work, we use a magnetic force microscope (MFM) operating under in-plane magnetic field in order to observe with high accuracy the domain configuration changes in Co nanowires as a function of the externally applied magnetic field.The main result is the quantitative evaluation of the coercive field of the individual nanostructures.Such characterization is performed by using an MFM-based technique in which a map of the magnetic signal is obtained as a function of both the lateral displacement and the magnetic field.

View Article: PubMed Central - HTML - PubMed

Affiliation: Instituto de Ciencia de Materiales de Madrid, CSIC, Madrid, 28049, Spain. aasenjo@icmm.csic.es.

ABSTRACT
High-resolution magnetic imaging is of utmost importance to understand magnetism at the nanoscale. In the present work, we use a magnetic force microscope (MFM) operating under in-plane magnetic field in order to observe with high accuracy the domain configuration changes in Co nanowires as a function of the externally applied magnetic field. The main result is the quantitative evaluation of the coercive field of the individual nanostructures. Such characterization is performed by using an MFM-based technique in which a map of the magnetic signal is obtained as a function of both the lateral displacement and the magnetic field.

No MeSH data available.


Topography and magnetic image of a typical region of the sample. (a) Topography and (b) MFM image of the array of nanowires (frequency shift contrast 11 Hz). Images size: 25.5 × 18.5 μm. Notice how the domain configuration is a function of the aspect ratio of the nanostructures (c) Nanowires domain configuration distribution as a function of their dimensions.
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Figure 1: Topography and magnetic image of a typical region of the sample. (a) Topography and (b) MFM image of the array of nanowires (frequency shift contrast 11 Hz). Images size: 25.5 × 18.5 μm. Notice how the domain configuration is a function of the aspect ratio of the nanostructures (c) Nanowires domain configuration distribution as a function of their dimensions.

Mentions: The MFM images of the whole array of Co nanowires measured in remanent state show the existence of different magnetic configuration as a function of the nanowire dimensions. The length of the nanowires is roughly constant (5.3 ± 0.1 μm) but the thickness varies between 20 to 140 nm and the width from 100 to 2,250 nm. The nanowires are well separated one from each other in order to avoid significant influence of dipolar interactions between nearby nanowires. Figure 1 displays the topography and the magnetic image of a typical region of the sample. Notice the evolution of the magnetic configuration from a multidomain structure (labeled A) to a single-domain state (labeled C). The largest nanostructures exhibit multidomain configuration in good agreement with magnetoresistance measurements on cobalt wires patterned by electron-beam lithography [31]. Nanowires narrower than 400 nm present single-domain state. In between, we distinguish nanostructures with rather complicated closure domain structure in their extremes (labeled B). Figure 1c shows the distribution of these three different configurations regarding the nanostructure width. For the wire dimensions reported here, the magnetization reversal is not expected to be influenced by structural defects. As previously discussed in Ref. [11], micromagnetic simulations support that the shape anisotropy is able to explain the main features of the magnetization reversal in this type of wires with dimensions around 200 nm in width. Thus, domain-wall pinning effects caused by structural defects are not expected for the wire dimensions studied here (width of 400 nm or larger) but only for much narrower wires.


Hysteresis loops of individual Co nanostripes measured by magnetic force microscopy.

Jaafar M, Serrano-Ramón L, Iglesias-Freire O, Fernández-Pacheco A, Ibarra MR, De Teresa JM, Asenjo A - Nanoscale Res Lett (2011)

Topography and magnetic image of a typical region of the sample. (a) Topography and (b) MFM image of the array of nanowires (frequency shift contrast 11 Hz). Images size: 25.5 × 18.5 μm. Notice how the domain configuration is a function of the aspect ratio of the nanostructures (c) Nanowires domain configuration distribution as a function of their dimensions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211502&req=5

Figure 1: Topography and magnetic image of a typical region of the sample. (a) Topography and (b) MFM image of the array of nanowires (frequency shift contrast 11 Hz). Images size: 25.5 × 18.5 μm. Notice how the domain configuration is a function of the aspect ratio of the nanostructures (c) Nanowires domain configuration distribution as a function of their dimensions.
Mentions: The MFM images of the whole array of Co nanowires measured in remanent state show the existence of different magnetic configuration as a function of the nanowire dimensions. The length of the nanowires is roughly constant (5.3 ± 0.1 μm) but the thickness varies between 20 to 140 nm and the width from 100 to 2,250 nm. The nanowires are well separated one from each other in order to avoid significant influence of dipolar interactions between nearby nanowires. Figure 1 displays the topography and the magnetic image of a typical region of the sample. Notice the evolution of the magnetic configuration from a multidomain structure (labeled A) to a single-domain state (labeled C). The largest nanostructures exhibit multidomain configuration in good agreement with magnetoresistance measurements on cobalt wires patterned by electron-beam lithography [31]. Nanowires narrower than 400 nm present single-domain state. In between, we distinguish nanostructures with rather complicated closure domain structure in their extremes (labeled B). Figure 1c shows the distribution of these three different configurations regarding the nanostructure width. For the wire dimensions reported here, the magnetization reversal is not expected to be influenced by structural defects. As previously discussed in Ref. [11], micromagnetic simulations support that the shape anisotropy is able to explain the main features of the magnetization reversal in this type of wires with dimensions around 200 nm in width. Thus, domain-wall pinning effects caused by structural defects are not expected for the wire dimensions studied here (width of 400 nm or larger) but only for much narrower wires.

Bottom Line: In the present work, we use a magnetic force microscope (MFM) operating under in-plane magnetic field in order to observe with high accuracy the domain configuration changes in Co nanowires as a function of the externally applied magnetic field.The main result is the quantitative evaluation of the coercive field of the individual nanostructures.Such characterization is performed by using an MFM-based technique in which a map of the magnetic signal is obtained as a function of both the lateral displacement and the magnetic field.

View Article: PubMed Central - HTML - PubMed

Affiliation: Instituto de Ciencia de Materiales de Madrid, CSIC, Madrid, 28049, Spain. aasenjo@icmm.csic.es.

ABSTRACT
High-resolution magnetic imaging is of utmost importance to understand magnetism at the nanoscale. In the present work, we use a magnetic force microscope (MFM) operating under in-plane magnetic field in order to observe with high accuracy the domain configuration changes in Co nanowires as a function of the externally applied magnetic field. The main result is the quantitative evaluation of the coercive field of the individual nanostructures. Such characterization is performed by using an MFM-based technique in which a map of the magnetic signal is obtained as a function of both the lateral displacement and the magnetic field.

No MeSH data available.