Name: scanning squid study of vortex manipulation by local contact
Uploaded: 2017-02-01T14:00:00
Description: Watch this Scientific Journal Video about Scanning SQUID Study of Vortex Manipulation by Local Contact at JoVE.com

We thank A. Sharoni from Bar-Ilan University for providing the superconducting films. This research was supported by European Research Council Grant ERC-2014-STG- 639792, Marie Curie Career Integration Grant FP7-PEOPLE-2012-CIG-333799, and Israel Science Foundation Grant ISF-1102/13.

1. Access to a Scanning SQUID System
<ol>
	<li>Use a scanning SQUID system that includes a SQUID sensor fabricated on a chip9,10, stick slip coarse motion stage, and a piezo-based scanner for fine motion. See Figure 1.</li>
	<li>Polish the SQUID chip into a corner around the pickup loop. The material of the chip needs to be removed all the way to the pickup loop.
	<ol>
		<li>Gently polish the SQUID, using a 5 to 0.5 &#181;m nonmagnetic polishin...

<ol>
	<li>Olson Reichhardt, C. J., Hastings, M. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Do+Vortices+Entangle?.">Do Vortices Entangle?.</a> Phys. Rev. Lett. 92, 157002 (2004).</li><li>Milo&#353;evi&#263;, M. V., Berdiyorov, G. R., Peeters, F. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluxonic+cellular+automata.">Fluxonic cellular automata.</a> Appl. Phys. Lett. 91, 212501 (2007).</li><li>Kalisky, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Scanning+Probe+Manipulation+of+Magnetism+at+the+LaAlO3/SrTiO3+Heterointerface.">Scanning Probe Manipulation of Magnetism at the LaAlO3/SrTiO3 Heterointerface.</a> Nano Lett. 12, 4055-4059 (2012).</li><li>Silva, C. C. D. S., Van de Vondel, J., Morelle, M., Moshchalkov, V. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled+multiple+reversals+of+a+ratchet+effect.">Controlled multiple reversals of a ratchet effect.</a> Nature. 440, 651-654 (2006).</li><li>Kalisky, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamics+of+single+vortices+in+grain+boundaries:+I-V+characteristics+on+the+femtovolt+scale.">Dynamics of single vortices in grain boundaries: I-V characteristics on the femtovolt scale.</a> Appl. Phys. Lett. 94, 202504 (2009).</li><li>Embon, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+dynamics+and+pinning+of+single+vortices+in+superconductors+at+nanometer+scales.">Probing dynamics and pinning of single vortices in superconductors at nanometer scales.</a> Sci. Rep. 5, 7598 (2015).</li><li>Auslaender, O. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanics+of+individual+isolated+vortices+in+a+cuprate+superconductor.">Mechanics of individual isolated vortices in a cuprate superconductor.</a> Nature Phys. 5, 35-39 (2008).</li><li>Kalisky, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Behavior+of+vortices+near+twin+boundaries+in+underdoped+Ba(Fe1-xCox)2As2.">Behavior of vortices near twin boundaries in underdoped Ba(Fe1-xCox)2As2.</a> Phys. Rev. B. 83, 064511 (2011).</li><li>Huber, M. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gradiometric+micro-SQUID+susceptometer+for+scanning+measurements+of+mesoscopic+samples.">Gradiometric micro-SQUID susceptometer for scanning measurements of mesoscopic samples.</a> Rev. Sci. Instrum. 79, 053704 (2008).</li><li>Koshnick, N. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+terraced+scanning+super+conducting+quantum+interference+device+susceptometer+with+submicron+pickup+loops.">A terraced scanning super conducting quantum interference device susceptometer with submicron pickup loops.</a> Appl. Phys. Lett. 93, 243101 (2008).</li><li>Kremen, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+Control+of+Individual+Superconducting+Vortices.">Mechanical Control of Individual Superconducting Vortices.</a> Nano Lett. 16, 1626-1630 (2016).</li></ol>

Successful manipulation of vortices depends on several critical steps. It is important to align the sensor at an angle, such that the tip of the chip will be the first to make contact with the sample. Second, it is important to note that the force exerted on the sample is determined by the mechanical properties of the cantilever that the chip is mounted on. In the elastic regime, the force applied is proportional to the deflection, x, according to Hooke&#39;s law: 
F = -kx
Where k is the ...

Vortices are magnetic objects at the nanoscale, formed in type 2 superconductors in the presence of external magnetic field. In a defect free sample, vortices can move freely. However, different defects in the material result in regions of reduced superconductivity which are energetically favorable for vortices. Vortices tend to decorate these regions, also known as the pinning sites. In this case, the force required to move a vortex must be greater than the pinning force. Properties of vortices, such as vortex density, interaction strength and range, can be easily determined by external field, temperature, or geometry of the sample. The ability to control these properties makes them a good model system for condensed matter behavior that can be easily tuned, as well as suitable candidates for electronic applications1,2. Control of the location of individual vortices is essential for the design of such logical elements.
Mechanical control of magnetic nanoparticles had been achieved before. Kalisky et al. recently used scanning superconducting quantum interference device (SQUID) to study the influence of local mechanical stress on ferromagnetic patches in complex oxide interfaces3. They were able to change the orientation of the patch by scanning in contact, pressing the tip of the SQUID into the sample, applying a force of up to 1 &#181;N in the process. We have used a similar method in our protocol in order to move vortices.
In existing studies of vortex manipulation, motion was achieved by applying current to the sample, thus creating Lorentz force4,5,6. While this method is effective, it is not local, and in order to control a single vortex, additional fabrication is required. Vortices can also be manipulated by applying external magnetic field, for example with a magnetic force microscope (MFM) or with a SQUID field coil7,8. This method is effective and local, but the force applied by these tools is small, and can overcome the pinning force only at high temperatures, close to the critical temperature of the superconductor. Our protocol allows effective, local manipulation at low temperatures (4 K) without additional fabrication of the sample.
We image vortices using scanning SQUID microscopy. The sensor is fabricated on a silicon chip which is polished into a corner, and glued on a flexible cantilever. The cantilever is used for capacitive sensing of the surface. The chip is placed at an angle to the sample, so that the contact point is at the tip of the chip. We apply forces of up to 2 &#181;N by pushing the chip into the sample. We move the sample relative to the SQUID by piezo elements. We move the vortex by tapping the silicon tip next to a vortex, or by sweeping it, touching the vortex.

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			<td height="21" style="height:21px;width:299px;">piezo elements</td>
			<td style="width:207px;">Piezo Systems Inc</td>
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			<td height="42" style="height:42px;width:299px;">low noise voltage preamplifier</td>
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			<td height="21" style="height:21px;width:299px;">dewar</td>
			<td style="width:207px;">Cryofab</td>
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			<td height="21" style="height:21px;width:299px;">vacuum cap</td>
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			<td height="21" style="height:21px;width:299px;">sputtering system</td>
			<td style="width:207px;">AJA international Inc</td>
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			<td height="21" style="height:21px;width:299px;">lapping film</td>
			<td style="width:207px;">3M</td>
			<td style="width:135px;">261X</td>
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			<td height="21" style="height:21px;width:299px;">Nb target</td>
			<td style="width:207px;">Kurt J. Lesker</td>
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			<td height="21" style="height:21px;width:299px;">GE Varnish</td>
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			<td>for cryogenic heatsinking</td>
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			<td height="22" style="height:22px;width:299px;">Silver paste</td>
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			<td style="width:135px;">05063-AB</td>
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scanning squid study of vortex manipulation by local contact

Local, deterministic manipulation of individual vortices in type 2 superconductors is challenging. The ability to control the position of individual vortices is necessary in order to study how vortices interact with each other, with the lattice, and with other magnetic objects. Here, we present a protocol for vortex manipulation in thin superconducting films by local contact, without applying current or magnetic field. Vortices are imaged using a scanning superconducting quantum interference device (SQUID), and vertical stress is applied to the sample by pushing the tip of a silicon chip into the sample, using a piezoelectric element. Vortices are moved by tapping the sample or sweeping it with the silicon tip. Our method allows for effective manipulation of individual vortices, without damaging the film or affecting its topography. We demonstrate how vortices were relocated to distances of up to 0.8 mm. The vortices remained stable at their new location up to five days. With this method, we can control vortices and move them to form complex configurations. This technique for vortex manipulation could also be implemented in applications such as vortex based logic devices.

Our protocol was successfully tested on thousands of individual, well separated vortices in two samples of Nb, and nine samples of NbN. We generate new vortices on the same sample by heating the sample above Tc, and cooling it back to 4.2 K in the presence of a magnetic field. We chose the external magnetic field to achieve the desired vortex density. We show here data from these experiments. These results have been described in detail by Kremen et al.11.<...

Watch this Scientific Journal Video about Scanning SQUID Study of Vortex Manipulation by Local Contact at JoVE.com

Scanning SQUID Study of Vortex Manipulation by Local Contact

We present a protocol for manipulation of individual vortices in thin superconducting films, using local mechanical contact. The method does not include applying current, magnetic field or additional fabrication steps.

Local, deterministic manipulation of individual vortices in type 2 superconductors is challenging. The ability to control the position of individual ...

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