{"id":79,"date":"2024-07-19T03:06:50","date_gmt":"2024-07-19T03:06:50","guid":{"rendered":"https:\/\/ktcn.edu.vn\/?page_id=79"},"modified":"2024-07-19T03:19:55","modified_gmt":"2024-07-19T03:19:55","slug":"vector-squids-microscope","status":"publish","type":"page","link":"https:\/\/ktcn.edu.vn\/?page_id=79","title":{"rendered":"Vector SQUIDs microscope"},"content":{"rendered":"\n

3D SQUID microscope based on the new principle<\/strong><\/p>\n\n\n\n

(1) Background<\/strong><\/p>\n\n\n\n

Most of conventional scanning SQUID microscopes typically raster a micro fabricated sensing coil in x-y <\/em>plane at a certain height z<\/em> above a sample, and measure the vertical component of magnetic field H<\/em>z<\/sub> in the sample surface. There are challenges and difficulties for a SQUID sensor to detect even a single electron spin and a magnetization vector of magnetic nano particle, which lead to potential applications in high density magnetic recording technology in the near future. The critical optimization requirement for nanometer-scale object detection is that the SQUID loop should be as small as the measurement scale. In fact, it is supposed that the SQUID loop dimension should be comparable to those of the magnetic nano object. There are many efforts to fabricate nano-sized pick up coil named as nano-SQUID sensor for detecting local magnetization of magnetic nano-particle [12] of nano-wire [13]. However, it is extremely difficult to manipulate specimen in direct contact with the SQUID loop and remove the sensor from the sample after doing measurement. Moreover, since the field sensitivity of SQUID increases linearly with pickup area, the sensitivity is limited when the size of pickup is reduced. There are strong demands for development of novel device in visualizing the three-dimensional information (size, orientation, position) of the magnetization of magnetic nanoscale object with reasonable resolution. My proposal would be very useful to fulfill such demands.<\/p>\n\n\n\n

References<\/strong><\/p>\n\n\n\n

[12]. L. Hao, D. Cox, P. See, J. Gallop and O. Kazakova, J. Phys. D: Appl. Phys. 43<\/strong> (2010) 474004.<\/p>\n\n\n\n

[13]. W. Wernsdorfer, et al., Phys. Rev. Lett. 77<\/strong> (1994) 9.<\/p>\n\n\n\n

(2) Our present study<\/strong><\/p>\n\n\n\n

I have been studying the vortex state of superconductor by using the scanning (SQUID) microscope, which is most sensitive among imaging instruments available for mapping surface local magnetic fields. The SQUID microscope performs a two-dimensional scanning in the horizontal plane at a certain height from sample surface to detect magnetic field distribution. While the scanning SQUID microscope (SSM) can achieve the best magnetic sensitivity of the order of nT (nano Tesla), the spatial resolution is limited typically to the size of the pickup loop (~10 \u03bcm). In requirement of improving resolution of images, a unique aspect of my research is the fruitful collaboration with leading theoretical scientists for restoring the high resolution image of SSM. Our method for improving the resolution of SSM is to apply an inverse transformation. <\/a>Fig. 2<\/a> show the sample is the superconducting Packman-shaped Mo80<\/sub>Ge20<\/sub> plate, opening <\/a>angle of sector defect of 90 degrees, diameter of 85 \u00b5m. At raw image data Fig. 2(a), we found failures of image such as the cracking was caused of contacting between sensor and sample. The curving of magnetics field caused the blur of sample boundary and the vortices near each other seem to be overlapped. By applying the numerical image processing technique, almost of cracking was removed effectivity (Fig. 2 <\/a>(b)), sharpness of the vortex profile is slightly improved, the diameter of Pacman was resorted similar with size of pattern (Fig. 2 (c)), vortex size is smaller and the distance of two neighboring vortex is more clear. This means that the resolution of the SSM is enhanced beyond the \u201cna\u00efve limitation\u201d of the pickup coil diameter and the processed data using an imaging filter developed by this works dramatically improves the spatial resolution. <\/p>\n\n\n\n

\n
\"\"<\/figure>\n<\/figure>\n\n\n\n

We optimized a vector SQUID sensor which was included a 3-dimensional (3D) scanning superconducting quantum interference device (SQUID) microscope base on previous study. To construct vector sensor, we fabricated three SQUID sensors on the same chip and each SQUID sensor has a pick-up coil. Three coils are configured in orthogonal with each other, respectively X, Y, Z<\/em> directions to measure the magnetic field vector. We also optimized the position of 3 coils. Follow way, we located 3 coils with their center at same line which made the distance between coils and sample are similar [17] (see Fig 5). This design will upgrade sensitive and reduce complicated in image processing. To confirm the proper operation of our SQUID sensor, we set a tiny coil about 30 turns and diameter of 3mm which is parallel and same center with z pickup coil [4]. This external magnetic field coil work in function of an extended vortex by curving of magnetic field around coil and main element of magnetic field is z direction. Fig 6 showed the F-V characteristic of x, y, z sensor respectively x, y, z elements of magnetic field. We found because of the curving of magnetic field from external coil, the vector SQUID sensor is not only catch z element magnetic field but it also take x and y elements of magnetic field. And the main element of magnetic field is z direction. Therefore, the amplitude of z element of magnetic field is larger than the amplitude of x, y elements of magnetic field. This results have been confirmed the fundamental characteristics of our vector SQUID sensors by take a vector of magnetic field. The F-V characteristic seem to be simple to study the fundamental characteristics of SQUID sensor but it is very restricted to rebuild an image of magnetic field. Therefore, we used a commercial Magnicon FLL readout electronics to connect with vector sensor. Fig 6 showed the voltage of Magnicon FLL readout are good linearity and a function of external magnetic field. The value of readout voltage also was confirmed by comparing the F0<\/sub> period of the F-V characteristics [14-16].<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

We have also designed a prototype model of the instrument. An XYZ<\/em> piezo-driven scanner with the range of 5 mm x 5 mm x 5 mm was used for controlling the position of the pick-up coils at low temperatures.<\/p>\n\n\n\n

Reference<\/strong><\/p>\n\n\n\n

[14] Vu The Dang, H. T. Huy, A. Ito, H. Miyoshi, M. Toji, S. Miyajima, H. Shishido, M. Maezawa, M. Hidaka, M. Hayashi, M. Kato and T. Ishida, “Scanning Vector SQUID Microcopy” JPS 72nd Annual Meeting, March 17 (Fri.) – 20 (Mon.), 2017, Osaka University<\/p>\n\n\n\n

[15]Vu The Dang, H. T. Huy, A. Ito, H. Miyoshi, M. Toji, S. Miyajima, H. Shishido, M. Maezawa, M. Hidaka, M. Hayashi, M. Kato and T. Ishida, “Scanning Microscopy of Vector SQUID Sensors” OPU Vortex Workshop on January 19-30, 2017, Osaka Prefecture University.<\/p>\n\n\n\n

[16]Vu The Dang, Ho Thanh Huy, Atsuki Ito, Hiroki Miyoshi, Masaki Toji, Shigeyuki Miyajima, Hiroaki Shishido, Masaaki Maezawa, Mutsuo Hidaka, Masahiko Hayashi, Masaru Kato and Takekazu Ishida, \u201cDevelopment of Scanning SQUID system for recovering vector magnetic fields\u201d Workshop of Radiation Center of Osaka Prefecture University, Nov 18, 2016.<\/p>\n\n\n\n

[17]Vu The Dang, Masaki Toji, Ho Thanh Huy, Shigeyuki Miyajima, Hiroaki Shishido, Mutsuo Hidaka, Masahiko Hayashi and Takekazu Ishida,”Vector sensor for scanning SQUID microscopy”  the 29th International Superconductivity Symposium (ISS2016), Tokyo International Forum on December 13\u221215, 2016, EDP1-2.<\/p>\n\n\n\n

(3) Purpose of proposed research<\/strong><\/p>\n\n\n\n

(1) To develop of novel scanning 3D SQUID microscope. This enables me to visualize the three-dimensional information (size, orientation, position) of the magnetization vector of nanometer-scale source(s). My study was constructed from combining of devices and software. Follow way, my research will eliminate physical limitation and safety for samples and sensor. Beside, data were caught in form of vector. Thus, they can be rebuilt much information by numerical processing algorithms. Therefore, my equipment can measure without contacting samples and scan one time at every site. This is very useful for nano samples and dynamic magnetics field. This features will develop many applications in future. That is main advantage of my study.<\/p>\n\n\n\n

(2) To clarify the magnetization dynamics of nanometer-size tiny objects (particles, wires, etc.). This is of critical importance for me in investigating nanoscale magnetic phenomena, spintronic, and organic functions in biological magnetic substances.<\/p>\n\n\n\n

The principle of three-dimensional SQUID microscope<\/strong><\/p>\n\n\n\n

The conventional scanning SQUID microscope (SSM) performs a two-dimensional XY scanning at a certain height above the sample surface, and is able to map out the vertical component of the magnetic distribution in the horizontal plane of sample. Prof. Masahiko Hayashi, myself, and collaborators [18] have developed image processing method by taking account of separation of the pickup coil and sample surface and perfect diamagnetism of pickup coil.<\/p>\n\n\n\n

The information on magnetic field sources or source currents can be reproduced by employing a so-called inverse problem, and I successfully demonstrated that the spatial resolution of SQUID microscope can be improved beautifully by using the inverse transformation in the Fourier space. By extending this path breaking principle, I propose to develop a novel three-dimensional scanning SQUID microscope, which is never available in the existing scientific technologies. This innovation makes it possible to detect not only the magnetic component of horizontal plane but also the vertical component, i.e., vector information of the local magnetic moment at any depth below the sample surface.<\/p>\n\n\n\n

Fig. 7 show the magnetization distribution within the sample:\u00a0(j <\/em>= 1, 2, 3, etc. are indices of magnetic moments in source points). The magnetization \u00a0of sample, as a source, can generate the magnetic field \u00a0at r<\/em><\/strong> in free space as<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n
\"\"<\/figure>\n\n\n\n

In Fig. 7, I explain the basic idea how to recover the magnetic moment vectors, which are not located on the surface but are buried in deep inside of the sample. I assume that the cubic mesh grid at the bottom contains several magnetic moments (or classic spins). The three dimensional planar grid at the top consists of observation points of \u00a0<\/em>by a SQUID sensor. From the freedom point of view, the contains all the information on the position, the amplitude, and direction of the magnetic moments, and hence it should be possible to recover them by solving the inverse Fourier transformation between \u00a0and. It is the idea of the 3D scanning SQUID microscope that the magnetic moments deep inside of the sample can be obtained by observing a magnetic field at outside of the sample or in free space at very near the surface. I consider that more detailed measurements of \u00a0would result in more precise recovery of the buried magnetic moments . I have to build the 3D SQUID microscope and the processing algorithms for reconstructing three-dimensional magnetic moments from the measured magnetic fields.<\/p>\n\n\n\n

References<\/strong><\/p>\n\n\n\n

[18]. M. Hayashi, H. Ebisawa, Ho Thanh Huy, T. Ishida, Appl. Phys. Lett 100<\/strong> (2012) 182601.<\/p>\n","protected":false},"excerpt":{"rendered":"

3D SQUID microscope based on the new principle (1) Background Most of conventional scanning SQUID microscopes typically raster a micro fabricated sensing coil in x-y plane at a certain height z above a sample, and measure the vertical component of magnetic field Hz in the sample surface. There are challenges and difficulties for a SQUID […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-79","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/ktcn.edu.vn\/index.php?rest_route=\/wp\/v2\/pages\/79","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ktcn.edu.vn\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/ktcn.edu.vn\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/ktcn.edu.vn\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ktcn.edu.vn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=79"}],"version-history":[{"count":4,"href":"https:\/\/ktcn.edu.vn\/index.php?rest_route=\/wp\/v2\/pages\/79\/revisions"}],"predecessor-version":[{"id":88,"href":"https:\/\/ktcn.edu.vn\/index.php?rest_route=\/wp\/v2\/pages\/79\/revisions\/88"}],"wp:attachment":[{"href":"https:\/\/ktcn.edu.vn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=79"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}