Pub Date : 2005-04-04DOI: 10.1109/INTMAG.2005.1464244
J. Fassbender, J. McCord, M. Weisheit, R. Mattheis
The static and dynamic magnetic properties of 20 nm thick permalloy films are studied as prepared and after Cr implantation with different Cr fluences. Doping results a decrease in the Curie temperature of the permalloy film with the implantation fluence. The magnetization damping is investigated by performing pulsed inductive microwave magnetometry (PIMM) for various applied magnetic fields. It is found that upon Cr implantation the PIMM amplitude decreases consistent with a decrease in the uniaxial anisotropy and a reduction in saturation magnetization. In contrast to this, a 7-fold increase of the magnetic damping is obtained for only 4% of the Cr doping.
{"title":"Increased magnetic damping of permalloy upon Cr implantation","authors":"J. Fassbender, J. McCord, M. Weisheit, R. Mattheis","doi":"10.1109/INTMAG.2005.1464244","DOIUrl":"https://doi.org/10.1109/INTMAG.2005.1464244","url":null,"abstract":"The static and dynamic magnetic properties of 20 nm thick permalloy films are studied as prepared and after Cr implantation with different Cr fluences. Doping results a decrease in the Curie temperature of the permalloy film with the implantation fluence. The magnetization damping is investigated by performing pulsed inductive microwave magnetometry (PIMM) for various applied magnetic fields. It is found that upon Cr implantation the PIMM amplitude decreases consistent with a decrease in the uniaxial anisotropy and a reduction in saturation magnetization. In contrast to this, a 7-fold increase of the magnetic damping is obtained for only 4% of the Cr doping.","PeriodicalId":273174,"journal":{"name":"INTERMAG Asia 2005. Digests of the IEEE International Magnetics Conference, 2005.","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126545951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-04-04DOI: 10.1109/INTMAG.2005.1464296
S. Gee, Y. Hong, F. Jeffers
In this paper, well-dispersed 50-60 nm sized spherical BaFe (S-BaFe) particles were synthesized and characterized. The magnetic and physical properties of both nanoparticles and S-BaFe magnetic tape were discussed. The coercivity, saturation magnetization, and remanent magnetic moment of the particles were 1568 Oe, 48.6 emu/g, and 28.9 emu/g, respectively.
{"title":"Synthesis of nano-sized spherical barium ferrite particles","authors":"S. Gee, Y. Hong, F. Jeffers","doi":"10.1109/INTMAG.2005.1464296","DOIUrl":"https://doi.org/10.1109/INTMAG.2005.1464296","url":null,"abstract":"In this paper, well-dispersed 50-60 nm sized spherical BaFe (S-BaFe) particles were synthesized and characterized. The magnetic and physical properties of both nanoparticles and S-BaFe magnetic tape were discussed. The coercivity, saturation magnetization, and remanent magnetic moment of the particles were 1568 Oe, 48.6 emu/g, and 28.9 emu/g, respectively.","PeriodicalId":273174,"journal":{"name":"INTERMAG Asia 2005. Digests of the IEEE International Magnetics Conference, 2005.","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125473476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-04-04DOI: 10.1109/INTMAG.2005.1464114
F. Tian, D. Wei, Jing Zhu
A new way to make high performance Ni nanowire arrays with external magnetic field inducing DC electrodeposition. The magnetic properties of the arrays are also studied by micromagnetic simulations. The electrodeposition of Ni nanowires is carried out in a two electrode electrodeposition pool. The deposition current is kept constant at 2 A/dm/sup 2/ with deposition time of 5 min and a 3000 Oe magnetic field along the wires is exerted parallel to the counter electrode direction. TEM photograph shows the nanowires are 600 nm long and polycrystalline. M-H loops for the Ni nanowires prepared with a magnetic field applied determine the squareness of 0.88 and coercivity of 690 Oe. Results of micromagnetic simulations show that the shape anisotropy field is dominant for the magnetic properties of a pure Ni elongated magnetic grain. Also, the simulated hysteresis loops agree quite well with the measured loops.
{"title":"Experimental and micromagnetics studies on magnetism of Ni nanowire arrays prepared with magnetic field induction","authors":"F. Tian, D. Wei, Jing Zhu","doi":"10.1109/INTMAG.2005.1464114","DOIUrl":"https://doi.org/10.1109/INTMAG.2005.1464114","url":null,"abstract":"A new way to make high performance Ni nanowire arrays with external magnetic field inducing DC electrodeposition. The magnetic properties of the arrays are also studied by micromagnetic simulations. The electrodeposition of Ni nanowires is carried out in a two electrode electrodeposition pool. The deposition current is kept constant at 2 A/dm/sup 2/ with deposition time of 5 min and a 3000 Oe magnetic field along the wires is exerted parallel to the counter electrode direction. TEM photograph shows the nanowires are 600 nm long and polycrystalline. M-H loops for the Ni nanowires prepared with a magnetic field applied determine the squareness of 0.88 and coercivity of 690 Oe. Results of micromagnetic simulations show that the shape anisotropy field is dominant for the magnetic properties of a pure Ni elongated magnetic grain. Also, the simulated hysteresis loops agree quite well with the measured loops.","PeriodicalId":273174,"journal":{"name":"INTERMAG Asia 2005. Digests of the IEEE International Magnetics Conference, 2005.","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125742947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-04-04DOI: 10.1109/INTMAG.2005.1463566
K. Kim, Young Ran Park, C. Kim, G. Ahn, J. Park
Magnetic and electronic properties of Fe- and Co-doped TiO/sub 2-/spl delta// thin films are investigated by vibrating sample magnetometer (VSM), Mossbauer spectroscopy, and X-ray photoelectron spectroscopy (XPS). When the precursor films are annealed in vacuum, the resulting oxygen-deficient TiO/sub 2-/spl delta//:Fe and TiO/sub 2-/spl delta//:Co films are found to become semiconducting with p-type carriers in the 10/sup 18/ cm/sup -3/ range. The oxygen-deficient films go through conductivity transitions from n-type to p-type by Fe and Co doping. Results of VSM measurements show that ferromagnetism is exhibited at room temperature. XPS measurements on the thin films reveal that Fe ions have both Fe/sup 2+/ and Fe/sup 3+/ ionic valences while Co ions have Co/sup 2+/ mostly. Also, the density of Fe/sup 2+/ ions is found to decrease after annealing.
{"title":"Diluted ferromagnetic properties in Fe- and Co-doped TiO/sub 2-/spl delta// thin films","authors":"K. Kim, Young Ran Park, C. Kim, G. Ahn, J. Park","doi":"10.1109/INTMAG.2005.1463566","DOIUrl":"https://doi.org/10.1109/INTMAG.2005.1463566","url":null,"abstract":"Magnetic and electronic properties of Fe- and Co-doped TiO/sub 2-/spl delta// thin films are investigated by vibrating sample magnetometer (VSM), Mossbauer spectroscopy, and X-ray photoelectron spectroscopy (XPS). When the precursor films are annealed in vacuum, the resulting oxygen-deficient TiO/sub 2-/spl delta//:Fe and TiO/sub 2-/spl delta//:Co films are found to become semiconducting with p-type carriers in the 10/sup 18/ cm/sup -3/ range. The oxygen-deficient films go through conductivity transitions from n-type to p-type by Fe and Co doping. Results of VSM measurements show that ferromagnetism is exhibited at room temperature. XPS measurements on the thin films reveal that Fe ions have both Fe/sup 2+/ and Fe/sup 3+/ ionic valences while Co ions have Co/sup 2+/ mostly. Also, the density of Fe/sup 2+/ ions is found to decrease after annealing.","PeriodicalId":273174,"journal":{"name":"INTERMAG Asia 2005. Digests of the IEEE International Magnetics Conference, 2005.","volume":"128 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126025087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-04-04DOI: 10.1109/INTMAG.2005.1464049
K. Tsukada, T. Kiwa, K. Ogata, T. Miyashita, A. Kandori
In this study, the spatial distribution of a cardiomagnetic vector field featuring multiple measurement planes obtained by separated distance was analyzed. Each of the vector components comprising a magnetocardiogram (MCG) and normal and tangential components are measured using an individual MCG measuring system respectively. Results on the overlapping time-wave forms of vector MCG in the case of a normal adult subject (40 years old) was presented. Where a localized single current source exists, each time-wave form must theoretically have a similar figure. However, the peak height ratios (Q, R, S, T) are different for each time-wave forms. On the other hand, the vector MCG time-wave forms of a 5 year old child showed a shape almost similar to that of adults, thought to be due to the relatively small size of the infant heart. However, it was observed that the vector fetal MCG was hardly influenced by a change by the fetal physique. For the next analysis of the vector MCG, changes in the magnetic field strength in distance z from the chest wall were measured. The magnetic field strength decreases according to the distance from the subject, although attenuation curves are different on each occasion This characteristic is the reflected difference in the current source depth in the heart. Here, another method was developed for current estimation using the attenuation factor of distance, which was obtained by calculating the change in the magnetic field strength against the distance r with 1/r/sup /spl alpha//. Current sources were estimated using the attenuation factor. This study showed that vector MCG measurement is helpful in the analysis of the current distribution.
{"title":"Spatial analysis of the three dimensional components of a magnetocardiogram","authors":"K. Tsukada, T. Kiwa, K. Ogata, T. Miyashita, A. Kandori","doi":"10.1109/INTMAG.2005.1464049","DOIUrl":"https://doi.org/10.1109/INTMAG.2005.1464049","url":null,"abstract":"In this study, the spatial distribution of a cardiomagnetic vector field featuring multiple measurement planes obtained by separated distance was analyzed. Each of the vector components comprising a magnetocardiogram (MCG) and normal and tangential components are measured using an individual MCG measuring system respectively. Results on the overlapping time-wave forms of vector MCG in the case of a normal adult subject (40 years old) was presented. Where a localized single current source exists, each time-wave form must theoretically have a similar figure. However, the peak height ratios (Q, R, S, T) are different for each time-wave forms. On the other hand, the vector MCG time-wave forms of a 5 year old child showed a shape almost similar to that of adults, thought to be due to the relatively small size of the infant heart. However, it was observed that the vector fetal MCG was hardly influenced by a change by the fetal physique. For the next analysis of the vector MCG, changes in the magnetic field strength in distance z from the chest wall were measured. The magnetic field strength decreases according to the distance from the subject, although attenuation curves are different on each occasion This characteristic is the reflected difference in the current source depth in the heart. Here, another method was developed for current estimation using the attenuation factor of distance, which was obtained by calculating the change in the magnetic field strength against the distance r with 1/r/sup /spl alpha//. Current sources were estimated using the attenuation factor. This study showed that vector MCG measurement is helpful in the analysis of the current distribution.","PeriodicalId":273174,"journal":{"name":"INTERMAG Asia 2005. Digests of the IEEE International Magnetics Conference, 2005.","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121446313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-04-04DOI: 10.1109/INTMAG.2005.1463514
T. Miyazaki, Y. Takahashi, S. Okamoto, O. Kitakami, Y. Shimada, Z. Akase, Y. Murakami, D. Shindo, K. Hono
In the present work, we investigate the size effect on the L1/sub 0/ ordering of FePt [001] epitaxial particles. From the dark field images using superlattice 110 spots, we clarify the critical size for L1/sub 0/ ordering of FePt. Furthermore, we investigate the order parameter S of each FePt nanoparticle from its electron diffraction pattern taken by nanometer-size electron beam, and clarify the relationship between the particle size d and the order parameter S. The present work has unambiguously shown that the ordering of L1/sub 0/ FePt is entirely suppressed when its size is less than d /spl sim/ 2 nm. Such size effect is not so serious for practical applications of FePt to permanent magnets or magnetic recording media, because the effect is significant only for d < 1.5 /spl sim/ 2 nm which is much smaller than the superparamagnetic limit of L1/sub 0/ FePt.
{"title":"Quantitative analysis of ordering of equiatomic FePt nanoparticles by electron diffraction","authors":"T. Miyazaki, Y. Takahashi, S. Okamoto, O. Kitakami, Y. Shimada, Z. Akase, Y. Murakami, D. Shindo, K. Hono","doi":"10.1109/INTMAG.2005.1463514","DOIUrl":"https://doi.org/10.1109/INTMAG.2005.1463514","url":null,"abstract":"In the present work, we investigate the size effect on the L1/sub 0/ ordering of FePt [001] epitaxial particles. From the dark field images using superlattice 110 spots, we clarify the critical size for L1/sub 0/ ordering of FePt. Furthermore, we investigate the order parameter S of each FePt nanoparticle from its electron diffraction pattern taken by nanometer-size electron beam, and clarify the relationship between the particle size d and the order parameter S. The present work has unambiguously shown that the ordering of L1/sub 0/ FePt is entirely suppressed when its size is less than d /spl sim/ 2 nm. Such size effect is not so serious for practical applications of FePt to permanent magnets or magnetic recording media, because the effect is significant only for d < 1.5 /spl sim/ 2 nm which is much smaller than the superparamagnetic limit of L1/sub 0/ FePt.","PeriodicalId":273174,"journal":{"name":"INTERMAG Asia 2005. Digests of the IEEE International Magnetics Conference, 2005.","volume":"113 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131943664","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-04-04DOI: 10.1109/INTMAG.2005.1463689
R. Wirix-Speetjens, W. Fyen, K. Xu, J. De Boeck, G. Borghs
Magnetic biosensors are emerging as promising alternatives for classical fluorescent-based micro-arrays, replacing the fluorescent label by a super-paramagnetic particle. While on-chip detection of magnetic particles is firmly established, research groups now start to explore the unique ability of manipulating these particles by applying controlled magnetic forces. In this paper, we describe the importance of magnetic, hydrodynamic and electrostatic forces in the actuation of magnetic particles. The use of magnetic actuation for biological applications in which aqueous solutions with high ionic strengths are often used, increases the need to study the effect of electrostatic forces into greater detail. We conclude that for transport of magnetic particles, suspended in aqueous solutions with a high ionic strength, the electrostatic force starts to become an important factor. Therefore, a quantitative study of air forces acting on the magnetic particle is necessary for a further development of magnetic force generating structures.
{"title":"On-chip magnetic particle transport: where physics, chemistry and biology meet","authors":"R. Wirix-Speetjens, W. Fyen, K. Xu, J. De Boeck, G. Borghs","doi":"10.1109/INTMAG.2005.1463689","DOIUrl":"https://doi.org/10.1109/INTMAG.2005.1463689","url":null,"abstract":"Magnetic biosensors are emerging as promising alternatives for classical fluorescent-based micro-arrays, replacing the fluorescent label by a super-paramagnetic particle. While on-chip detection of magnetic particles is firmly established, research groups now start to explore the unique ability of manipulating these particles by applying controlled magnetic forces. In this paper, we describe the importance of magnetic, hydrodynamic and electrostatic forces in the actuation of magnetic particles. The use of magnetic actuation for biological applications in which aqueous solutions with high ionic strengths are often used, increases the need to study the effect of electrostatic forces into greater detail. We conclude that for transport of magnetic particles, suspended in aqueous solutions with a high ionic strength, the electrostatic force starts to become an important factor. Therefore, a quantitative study of air forces acting on the magnetic particle is necessary for a further development of magnetic force generating structures.","PeriodicalId":273174,"journal":{"name":"INTERMAG Asia 2005. Digests of the IEEE International Magnetics Conference, 2005.","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129986069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-04-04DOI: 10.1109/INTMAG.2005.1463993
M. Sekino, A. Kaneko, S. Ueno
Diffusion tensor magnetic resonance (MR) images reflect structure of cell membranes as well as the self-diffusion coefficient of water. A change in the geometry of cell membrane affects diffusion tensor images, which suggests a potential for a new method of strain mapping. In this study, we investigated the effect of strain on diffusion tensor images of muscles using numerical simulation and animal experiments. The finite difference method was used to calculate the signal intensities of diffusion tensor images. To investigate the effect of strain, the aspect ratio of the model was varied from 1.0 to 4.0, which corresponded to varying strain from 0.0 to 1.0. The apparent diffusion coefficient (ADC), the mean diffusivity (MD), and the fractional anisotropy (FA) were calculated for each aspect ratio in the presence and absence of strain. Diffusion tensor images of the isolated frog gastrocnemius muscle were obtained using a 4.7 T MR imaging system. Results indicate that the ADC monotonically increases with strain. The MD decreased with the compression due to a decrease in the cross-sectional area. The FA also decreased with the compression because a decrease in the diffusion tensor parameter D/sub xx/ caused a decrease in diffusion anisotropy.
{"title":"Mapping strain in biological tissues using magnetic resonance","authors":"M. Sekino, A. Kaneko, S. Ueno","doi":"10.1109/INTMAG.2005.1463993","DOIUrl":"https://doi.org/10.1109/INTMAG.2005.1463993","url":null,"abstract":"Diffusion tensor magnetic resonance (MR) images reflect structure of cell membranes as well as the self-diffusion coefficient of water. A change in the geometry of cell membrane affects diffusion tensor images, which suggests a potential for a new method of strain mapping. In this study, we investigated the effect of strain on diffusion tensor images of muscles using numerical simulation and animal experiments. The finite difference method was used to calculate the signal intensities of diffusion tensor images. To investigate the effect of strain, the aspect ratio of the model was varied from 1.0 to 4.0, which corresponded to varying strain from 0.0 to 1.0. The apparent diffusion coefficient (ADC), the mean diffusivity (MD), and the fractional anisotropy (FA) were calculated for each aspect ratio in the presence and absence of strain. Diffusion tensor images of the isolated frog gastrocnemius muscle were obtained using a 4.7 T MR imaging system. Results indicate that the ADC monotonically increases with strain. The MD decreased with the compression due to a decrease in the cross-sectional area. The FA also decreased with the compression because a decrease in the diffusion tensor parameter D/sub xx/ caused a decrease in diffusion anisotropy.","PeriodicalId":273174,"journal":{"name":"INTERMAG Asia 2005. Digests of the IEEE International Magnetics Conference, 2005.","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130143344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-04-04DOI: 10.1109/INTMAG.2005.1464377
S. Cheng, Y. Chou, J.G. Lin
In this work, ionic size or the radius of A-site cation was utilized for the fine-tuning of the magnetoresistance (MR) of Nd/sub 0.5/Ca/sub 0.5-y/Sr/sub y/MnO/sub 3/. The values of were set to be from 1.182 /spl Aring/ to 1.20 /spl Aring/. The highest MR ratio was obtained to be /spl sim/ 800% at 50 K in the samples with y = 0.08. Furthermore, the "spin valve" like behavior was observed at 100 K at the same sample, which may have originated from the melting of charge ordering.
{"title":"Fine-tuning of magnetoresistance in Nd/sub 0.5/(Ca,Sr)/sub 0.5/MnO/sub 3/ system","authors":"S. Cheng, Y. Chou, J.G. Lin","doi":"10.1109/INTMAG.2005.1464377","DOIUrl":"https://doi.org/10.1109/INTMAG.2005.1464377","url":null,"abstract":"In this work, ionic size or the radius of A-site cation was utilized for the fine-tuning of the magnetoresistance (MR) of Nd/sub 0.5/Ca/sub 0.5-y/Sr/sub y/MnO/sub 3/. The values of were set to be from 1.182 /spl Aring/ to 1.20 /spl Aring/. The highest MR ratio was obtained to be /spl sim/ 800% at 50 K in the samples with y = 0.08. Furthermore, the \"spin valve\" like behavior was observed at 100 K at the same sample, which may have originated from the melting of charge ordering.","PeriodicalId":273174,"journal":{"name":"INTERMAG Asia 2005. Digests of the IEEE International Magnetics Conference, 2005.","volume":"97 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134080440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-04-04DOI: 10.1109/INTMAG.2005.1464214
S. Yuasa, H. Kubota, A. Fukushima, T. Nagahama, T. Katayama, Y. Suzuki, K. Ando
A fully epitaxial Fe(001)/MgO(001)/Fe(001) magnetic tunnel junctions were fabricated using electron beam evaporation under ultrahigh vacuum and achieved a giant tunneling magnetoresistance (TMR) effect over 180% at room temperature. The magnetoresistance (MR) ratio for the crystalline MgO(001) tunnel barrier is about three times that for the amorphous Al-O barrier indicating an importance of the crystalline symmetry of tunnel barrier for the coherent tunneling of /spl Delta//sub 1/ electrons. The MTJs with crystalline MgO(001) tunnel barrier also have high thermal stability and reproducibility of TMR. An oscillation of the TMR effect was also observed as a function of the thickness of MgO tunnel barrier, which could be a direct evidence of coherent spin-dependent tunneling. Such conservation of the coherency of spin polarized electron across the tunnel barrier will enable us to develop a variety of novel spintronics devices with quantum mechanical functions.
{"title":"Coherent spin-dependent tunneling in magnetic tunnel junctions with MgO(001) tunnel barrier","authors":"S. Yuasa, H. Kubota, A. Fukushima, T. Nagahama, T. Katayama, Y. Suzuki, K. Ando","doi":"10.1109/INTMAG.2005.1464214","DOIUrl":"https://doi.org/10.1109/INTMAG.2005.1464214","url":null,"abstract":"A fully epitaxial Fe(001)/MgO(001)/Fe(001) magnetic tunnel junctions were fabricated using electron beam evaporation under ultrahigh vacuum and achieved a giant tunneling magnetoresistance (TMR) effect over 180% at room temperature. The magnetoresistance (MR) ratio for the crystalline MgO(001) tunnel barrier is about three times that for the amorphous Al-O barrier indicating an importance of the crystalline symmetry of tunnel barrier for the coherent tunneling of /spl Delta//sub 1/ electrons. The MTJs with crystalline MgO(001) tunnel barrier also have high thermal stability and reproducibility of TMR. An oscillation of the TMR effect was also observed as a function of the thickness of MgO tunnel barrier, which could be a direct evidence of coherent spin-dependent tunneling. Such conservation of the coherency of spin polarized electron across the tunnel barrier will enable us to develop a variety of novel spintronics devices with quantum mechanical functions.","PeriodicalId":273174,"journal":{"name":"INTERMAG Asia 2005. Digests of the IEEE International Magnetics Conference, 2005.","volume":"140 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131887996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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