Y. Shiratsuchi, J. Shen, Y. Tao, K. Takahara, K. Toyoki, R. Nakatani
Perpendicular exchange bias using magnetoelectric Cr 2 O 3 has an electric-field triggered switching ability, and the thickness limit of the Cr 2 O 3 layer for inducing this bias is a topic of research. In this paper, we investigated the structural, magnetic, and electric properties of Pt/Co/Au/Cr 2 O 3 /Pt thin films with a Cr 2 O 3 layer in the thickness range of 5.7 to 25 nm. By using a magnetron sputtering method, a well-crystallized Cr 2 O 3 (0001) layer was formed in 5.7-nm-thick Cr 2 O 3 . All studied films showed perpendicular magnetic anisotropy. The uniaxial magnetic anisotropy energy density increased as the Cr 2 O 3 thickness decreased, and 810±90 kJ/m 3 was obtained for the film with 5.7-nm-thick Cr 2 O 3 . Perpendicular exchange bias was evaluated above 80 K, and an exchange anisotropy energy density of 0.30 mJ/m 2 was observed for the film with a 25-nm-thick Cr 2 O 3 at 80 K. The exchange bias could not be observed below 18 nm. Instead, coercivity enhancement, which yields the exchange bias by precisely controlling interfacial exchange coupling, was observed. The electric resistivity was about 5 10 5 ·m for the 5.7-nm-thick Cr 2 O 3 layer, which is sufficiently high for magnetoelectric applications.
{"title":"Structural, Magnetic, and Electric Properties of Pt/Co/Au/Cr2O3/Pt Thin Film with Cr2O3 Layer below 25 nm","authors":"Y. Shiratsuchi, J. Shen, Y. Tao, K. Takahara, K. Toyoki, R. Nakatani","doi":"10.3379/MSJMAG.2107R004","DOIUrl":"https://doi.org/10.3379/MSJMAG.2107R004","url":null,"abstract":"Perpendicular exchange bias using magnetoelectric Cr 2 O 3 has an electric-field triggered switching ability, and the thickness limit of the Cr 2 O 3 layer for inducing this bias is a topic of research. In this paper, we investigated the structural, magnetic, and electric properties of Pt/Co/Au/Cr 2 O 3 /Pt thin films with a Cr 2 O 3 layer in the thickness range of 5.7 to 25 nm. By using a magnetron sputtering method, a well-crystallized Cr 2 O 3 (0001) layer was formed in 5.7-nm-thick Cr 2 O 3 . All studied films showed perpendicular magnetic anisotropy. The uniaxial magnetic anisotropy energy density increased as the Cr 2 O 3 thickness decreased, and 810±90 kJ/m 3 was obtained for the film with 5.7-nm-thick Cr 2 O 3 . Perpendicular exchange bias was evaluated above 80 K, and an exchange anisotropy energy density of 0.30 mJ/m 2 was observed for the film with a 25-nm-thick Cr 2 O 3 at 80 K. The exchange bias could not be observed below 18 nm. Instead, coercivity enhancement, which yields the exchange bias by precisely controlling interfacial exchange coupling, was observed. The electric resistivity was about 5 10 5 ·m for the 5.7-nm-thick Cr 2 O 3 layer, which is sufficiently high for magnetoelectric applications.","PeriodicalId":36791,"journal":{"name":"Journal of the Magnetics Society of Japan","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82484046","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}
We examine the adjacent track interference (ATI) problem that arises during three-dimensional heat-assisted magnetic recording (3D HAMR) at 2 Tbpsi per layer (total density of 4 Tbpsi) where the medium consists of a high Curie temperature (HC) layer and a low Curie temperature (LC) layer. To evaluate the grain error distribution, the expected magnetization value is calculated using the grain error probability. Prior to considering the ATI in 3D HAMR, we examine the ATI problem for conventional HAMR. Since the temperature of the LC layer in the adjacent tracks while writing in the HC layer (HC writing) exceeds the LC Curie temperature, HC writing will erase the data of the LC layer in the adjacent tracks. Therefore, we investigate 3D HAMR combined with shingled magnetic recording. The ATI in an LC (upper, namely, surface) / HC (lower) layer structure is compared with that in an HC / LC layer structure. The latter is disadvantageous in relation to ATI caused by the small thermal gradient in the LC layer.
{"title":"Adjacent Track Interference in Three-Dimensional Heat-Assisted Magnetic Recording","authors":"T. Kobayashi, Y. Nakatani, Y. Fujiwara","doi":"10.3379/MSJMAG.2107R003","DOIUrl":"https://doi.org/10.3379/MSJMAG.2107R003","url":null,"abstract":"We examine the adjacent track interference (ATI) problem that arises during three-dimensional heat-assisted magnetic recording (3D HAMR) at 2 Tbpsi per layer (total density of 4 Tbpsi) where the medium consists of a high Curie temperature (HC) layer and a low Curie temperature (LC) layer. To evaluate the grain error distribution, the expected magnetization value is calculated using the grain error probability. Prior to considering the ATI in 3D HAMR, we examine the ATI problem for conventional HAMR. Since the temperature of the LC layer in the adjacent tracks while writing in the HC layer (HC writing) exceeds the LC Curie temperature, HC writing will erase the data of the LC layer in the adjacent tracks. Therefore, we investigate 3D HAMR combined with shingled magnetic recording. The ATI in an LC (upper, namely, surface) / HC (lower) layer structure is compared with that in an HC / LC layer structure. The latter is disadvantageous in relation to ATI caused by the small thermal gradient in the LC layer.","PeriodicalId":36791,"journal":{"name":"Journal of the Magnetics Society of Japan","volume":"547 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78172490","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}
Yuta Kobayashi, Tetsuya Ikebuchi, Y. Shiota, T. Ono, T. Moriyama
Chiral antiferromagnets have recently been drawing attention due to their unique magnetic transport properties such as the giant anomalous Hall effect. We previously reported an experimental demonstration of the giant anomalous Hall effect in the chiral antiferromagnet Mn3Ir thin films with quite blunt hysteresis curves suggesting a large distribution of magnetic properties associated with magnetic domains. In this work, we measured the anomalous Hall effect and its hysteresis curve in the Mn3Ir of various device sizes. By comparing the experimental data with our developed statistical model, we characterize a distribution of the magnetic domain size in our Mn3Ir films.
{"title":"Estimation of Magnetic Domain Size in Chiral Antiferromagnet Mn3Ir by the Anomalous Hall Measurements","authors":"Yuta Kobayashi, Tetsuya Ikebuchi, Y. Shiota, T. Ono, T. Moriyama","doi":"10.3379/MSJMAG.2107L002","DOIUrl":"https://doi.org/10.3379/MSJMAG.2107L002","url":null,"abstract":"Chiral antiferromagnets have recently been drawing attention due to their unique magnetic transport properties such as the giant anomalous Hall effect. We previously reported an experimental demonstration of the giant anomalous Hall effect in the chiral antiferromagnet Mn3Ir thin films with quite blunt hysteresis curves suggesting a large distribution of magnetic properties associated with magnetic domains. In this work, we measured the anomalous Hall effect and its hysteresis curve in the Mn3Ir of various device sizes. By comparing the experimental data with our developed statistical model, we characterize a distribution of the magnetic domain size in our Mn3Ir films.","PeriodicalId":36791,"journal":{"name":"Journal of the Magnetics Society of Japan","volume":"29 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90845723","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}
MgO/Fe/Au(001) and Au/Fe/Au(001) trilayers with Fe layer thickness from 0.4 to 1.2 nm were grown by the molecular beam epitaxy (MBE) method, and the perpendicular magnetic anisotropy (PMA) and magnetization dynamics of the trilayers were studied. The MgO/Fe/Au trilayer exhibited a slightly larger interface anisotropy than the Au/Fe/Au trilayer, and the effective anisotropy of both trilayers decreased with increasing Fe thickness due to the shape anisotropy. The g-factor of both trilayers decreased from the bulk value with decreasing Fe thickness, and MgO/Fe/Au showed a slightly lower g-factor than Au/Fe/Au. The effective damping constant a of both trilayers increased with decreasing Fe thickness due to the effect of spin pumping, and interestingly the MgO/Fe/Au trilayers showed large damping compared with the Au/Fe/Au ones. These results suggest that the broken inversion symmetry in MgO/Fe/Au leads to a large PMA and damping through Rashba spin-orbit coupling.
{"title":"Perpendicular Anisotropy and Damping of MBE-grown MgO/Fe/Au(001) and Au/Fe/Au(001) Trilayers","authors":"N. Kamiya, D. Oshima, S. Iwata, T. Kato","doi":"10.3379/MSJMAG.2107R005","DOIUrl":"https://doi.org/10.3379/MSJMAG.2107R005","url":null,"abstract":"MgO/Fe/Au(001) and Au/Fe/Au(001) trilayers with Fe layer thickness from 0.4 to 1.2 nm were grown by the molecular beam epitaxy (MBE) method, and the perpendicular magnetic anisotropy (PMA) and magnetization dynamics of the trilayers were studied. The MgO/Fe/Au trilayer exhibited a slightly larger interface anisotropy than the Au/Fe/Au trilayer, and the effective anisotropy of both trilayers decreased with increasing Fe thickness due to the shape anisotropy. The g-factor of both trilayers decreased from the bulk value with decreasing Fe thickness, and MgO/Fe/Au showed a slightly lower g-factor than Au/Fe/Au. The effective damping constant a of both trilayers increased with decreasing Fe thickness due to the effect of spin pumping, and interestingly the MgO/Fe/Au trilayers showed large damping compared with the Au/Fe/Au ones. These results suggest that the broken inversion symmetry in MgO/Fe/Au leads to a large PMA and damping through Rashba spin-orbit coupling.","PeriodicalId":36791,"journal":{"name":"Journal of the Magnetics Society of Japan","volume":"22 4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89887297","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}
In previous research, we have developed a reluctance network analysis (RNA) to calculate various electric machines ’ characteristics, including electric motors, with high accuracy and high speed. However, those researches were limited to the closed magnetic circuits. This paper presents a novel RNA model for open magnetic circuits with the Kelvin transformation concept. The proposed method applies to analyzing the particle accelerator magnets, wireless power transfer systems, etc.
{"title":"A Novel Reluctance Network Model Applicable for Open Magnetic Circuits","authors":"Y. Hane, K. Sugahara, K. Nakamura","doi":"10.3379/MSJMAG.2107R006","DOIUrl":"https://doi.org/10.3379/MSJMAG.2107R006","url":null,"abstract":"In previous research, we have developed a reluctance network analysis (RNA) to calculate various electric machines ’ characteristics, including electric motors, with high accuracy and high speed. However, those researches were limited to the closed magnetic circuits. This paper presents a novel RNA model for open magnetic circuits with the Kelvin transformation concept. The proposed method applies to analyzing the particle accelerator magnets, wireless power transfer systems, etc.","PeriodicalId":36791,"journal":{"name":"Journal of the Magnetics Society of Japan","volume":"72 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89623906","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}
Void-defect induced magnetism of graphene molecule was recently reported in our previous paper of this series study. This paper investigated the case of hydrogenated graphene molecule, in chemical term, polycyclic aromatic hydrocarbon (PAH). Molecular infrared spectrum obtained by density functional theory was compared with astronomical observation. Void-defect on PAH caused serious structure change. Typical example of C 23 H 12 had two carbon pentagon rings among hexagon networks. Stable spin state was non-magnetic singlet state. This is contrary to pure carbon case of C 23 , which show magnetic triplet state. It was discussed that Hydrogen played an important role to diminish magnetism by creating an SP3-bond among SP2-networks. Such a structure change affected molecular vibration and finally to photoemission spectrum in infrared region. The dication-C 23 H 12 showed featured bands at 3.2, 6.3, 7.7, 8.6, 11.2, and 12.7 micrometer. It was surprising that those calculated bands coincided well with astronomically observed bands in many planetary nebulae. To confirm our study, large size molecule of C 53 H 18 was studied. Calculation reproduced again similar astronomical bands. Also, small size molecule of C 12 H 8 showed good coincidence with the spectrum observed for young stars. This paper would be the first report to indicate the specific PAH in space.
{"title":"Void-Defect Induced Magnetism and Structure Change of Carbon Material-Ⅲ: Hydrocarbon Molecules","authors":"N. Ota, Aigen Li, L. Nemes","doi":"10.3379/msjmag.2107R014","DOIUrl":"https://doi.org/10.3379/msjmag.2107R014","url":null,"abstract":"Void-defect induced magnetism of graphene molecule was recently reported in our previous paper of this series study. This paper investigated the case of hydrogenated graphene molecule, in chemical term, polycyclic aromatic hydrocarbon (PAH). Molecular infrared spectrum obtained by density functional theory was compared with astronomical observation. Void-defect on PAH caused serious structure change. Typical example of C 23 H 12 had two carbon pentagon rings among hexagon networks. Stable spin state was non-magnetic singlet state. This is contrary to pure carbon case of C 23 , which show magnetic triplet state. It was discussed that Hydrogen played an important role to diminish magnetism by creating an SP3-bond among SP2-networks. Such a structure change affected molecular vibration and finally to photoemission spectrum in infrared region. The dication-C 23 H 12 showed featured bands at 3.2, 6.3, 7.7, 8.6, 11.2, and 12.7 micrometer. It was surprising that those calculated bands coincided well with astronomically observed bands in many planetary nebulae. To confirm our study, large size molecule of C 53 H 18 was studied. Calculation reproduced again similar astronomical bands. Also, small size molecule of C 12 H 8 showed good coincidence with the spectrum observed for young stars. This paper would be the first report to indicate the specific PAH in space.","PeriodicalId":36791,"journal":{"name":"Journal of the Magnetics Society of Japan","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78826248","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}
Void-defect is a possible origin of ferromagnetic feature on pure carbon materials. In our previous paper, void-defect on graphene-nanoribbon show highly polarized spin configuration. In this paper, we studied cases for graphene molecules by quantum theory, by astronomical observation and by laboratory experiment. Model molecules for the density functional theory are graphene molecules of C23 and C53 induced by a void-defect. They have carbon pentagon ring within a hexagon network. Single void has three radical carbons, holding six spins. Those spins make several spin-states, which affects to molecular structure and molecular vibration, finally to infrared spectrum. The stable spin state was triplet, not singlet. This suggests magnetic pure carbon molecule. It was a surprise that those molecules show close infrared spectrum with astronomically observed one, especially observed on carbon rich planetary nebulae. We could assign major band at 18.9 micrometer, and sub-bands at 6.6, 7.0, 7.6, 8.1, 8.5, 9.0 and 17.4 micrometer. Also, calculated spectrum roughly coincides with that of laboratory experiment by the laser-induced carbon plasma, which is an analogy of cosmic carbon creation in interstellar space. [To be published on Journal of the Magnetics Society of Japan (2021), e-mail to Norio Ota: n-otajitaku@nifty.com ]
{"title":"Void-Defect Induced Magnetism and Structure Change of Carbon Material-Ⅱ: Graphene Molecules","authors":"N. Ota, Aigen Li, L. Nemes, M. Otsuka","doi":"10.3379/MSJMAG.2103R007","DOIUrl":"https://doi.org/10.3379/MSJMAG.2103R007","url":null,"abstract":"Void-defect is a possible origin of ferromagnetic feature on pure carbon materials. In our previous paper, void-defect on graphene-nanoribbon show highly polarized spin configuration. In this paper, we studied cases for graphene molecules by quantum theory, by astronomical observation and by laboratory experiment. Model molecules for the density functional theory are graphene molecules of C23 and C53 induced by a void-defect. They have carbon pentagon ring within a hexagon network. Single void has three radical carbons, holding six spins. Those spins make several spin-states, which affects to molecular structure and molecular vibration, finally to infrared spectrum. The stable spin state was triplet, not singlet. This suggests magnetic pure carbon molecule. It was a surprise that those molecules show close infrared spectrum with astronomically observed one, especially observed on carbon rich planetary nebulae. We could assign major band at 18.9 micrometer, and sub-bands at 6.6, 7.0, 7.6, 8.1, 8.5, 9.0 and 17.4 micrometer. Also, calculated spectrum roughly coincides with that of laboratory experiment by the laser-induced carbon plasma, which is an analogy of cosmic carbon creation in interstellar space. [To be published on Journal of the Magnetics Society of Japan (2021), e-mail to Norio Ota: n-otajitaku@nifty.com ]","PeriodicalId":36791,"journal":{"name":"Journal of the Magnetics Society of Japan","volume":"31 1","pages":"41-49"},"PeriodicalIF":0.0,"publicationDate":"2021-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78252325","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}
We investigated both the Seebeck and anomalous Nernst e ff ects in NiCo 2 O 4 (001) epitaxial films with a preferential magnetization direction normal to the film plane. Since the thermoelectric signals were extremely small, we custom-built a measurement system to detect the weak voltage signals. To suppress spurious voltage signals originating from the electrical contacts in the measurement circuit, we employed the following measures. We reduced the number of electrical contacts between the output of a commercial cryostat with a superconducting magnet and the nano-voltmeters. We employed silver soldering while making the electrical contacts to reduce the thermal electromotive force voltages at the remaining contacts. By adopting these measures, we have succeeded in detecting thermoelectric voltages as small as 5 nV. The observed thermoelectric e ffi ciency of NiCo 2 O 4 is quite small compared to conventional ferromagnetic metals.
{"title":"Anomalous Nernst and Seebeck Effects in NiCo2O4 Films","authors":"H. Koizumi, A. Hidaka, T. Komine, H. Yanagihara","doi":"10.3379/MSJMAG.2103R006","DOIUrl":"https://doi.org/10.3379/MSJMAG.2103R006","url":null,"abstract":"We investigated both the Seebeck and anomalous Nernst e ff ects in NiCo 2 O 4 (001) epitaxial films with a preferential magnetization direction normal to the film plane. Since the thermoelectric signals were extremely small, we custom-built a measurement system to detect the weak voltage signals. To suppress spurious voltage signals originating from the electrical contacts in the measurement circuit, we employed the following measures. We reduced the number of electrical contacts between the output of a commercial cryostat with a superconducting magnet and the nano-voltmeters. We employed silver soldering while making the electrical contacts to reduce the thermal electromotive force voltages at the remaining contacts. By adopting these measures, we have succeeded in detecting thermoelectric voltages as small as 5 nV. The observed thermoelectric e ffi ciency of NiCo 2 O 4 is quite small compared to conventional ferromagnetic metals.","PeriodicalId":36791,"journal":{"name":"Journal of the Magnetics Society of Japan","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87890600","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}
We examine a medium layer structure in three-dimensional heat-assisted magnetic recording (3D HAMR) at 2 Tbpsi per layer (total density of 4 Tbpsi) where the medium consists of a high Curie temperature (HC) layer and a low Curie temperature (LC) layer. We perform a heat transfer simulation for 3D HAMR media including the isolation layer. To evaluate the grain error distribution, the expected value of the magnetization is calculated using the grain error probability. The error threshold and the time dependence of the bit error rate are discussed for 10 years of archiving. The information stability in the HC layer while writing in the LC layer is estimated using the temperature profile calculated by the heat transfer simulation. An LC (upper, namely, surface) / HC (lower) layer structure is compared with an HC (upper) / LC (lower) layer structure. The former is disadvantageous in relation to the medium surface temperature as regards writing in the HC layer. The latter may be disadvantageous in relation to the difference between the thermal gradients for HC and LC writing.
{"title":"Medium Layer Structure in Three-Dimensional Heat-Assisted Magnetic Recording","authors":"T. Kobayashi, Y. Nakatani, Y. Fujiwara","doi":"10.3379/msjmag.2103r03","DOIUrl":"https://doi.org/10.3379/msjmag.2103r03","url":null,"abstract":"We examine a medium layer structure in three-dimensional heat-assisted magnetic recording (3D HAMR) at 2 Tbpsi per layer (total density of 4 Tbpsi) where the medium consists of a high Curie temperature (HC) layer and a low Curie temperature (LC) layer. We perform a heat transfer simulation for 3D HAMR media including the isolation layer. To evaluate the grain error distribution, the expected value of the magnetization is calculated using the grain error probability. The error threshold and the time dependence of the bit error rate are discussed for 10 years of archiving. The information stability in the HC layer while writing in the LC layer is estimated using the temperature profile calculated by the heat transfer simulation. An LC (upper, namely, surface) / HC (lower) layer structure is compared with an HC (upper) / LC (lower) layer structure. The former is disadvantageous in relation to the medium surface temperature as regards writing in the HC layer. The latter may be disadvantageous in relation to the difference between the thermal gradients for HC and LC writing.","PeriodicalId":36791,"journal":{"name":"Journal of the Magnetics Society of Japan","volume":"40 10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89977696","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}
Void-defect is a possible origin of ferromagnetic-like feature of pure carbon material. Applying density functional theory to void-defect induced graphene-nano-ribbon (GNR), a detailed relationship between multiple-spin-state and structure change was studied. An equilateral triangle of an initial void having six electrons is distorted to isosceles triangle by re-bonding carbon atoms. Among possible spin-states of Sz=0/2, 2/2, 4/2 and 6/2, the most stable state was Sz=2/2. The case of Sz=4/2 is remarkable that initial flat ribbon turned to three dimensionally curled one having highly polarized spin configuration at ribbon edges. Total energy of Sz=4/2 was very close to that of Sz=2/2, which suggests coexistence of flat ribbon and curled ribbon. As a model of three dimensional graphite, bi-layered AB stacked GNR was analyzed for cases of different void position of α-site and β-site. Spin distribution was limited to the surface layer, nothing to the back layer. Distorted void triangle show 60degree clockwise rotation from αto β-site, which was consistent with experimental observation using the scanning tunneling microscope. This study revealed that void-defect in GNR induces unusual polarized spin state, different with usual ferromagnetic one. [ To be published on Journal of the Magnetics Society of Japan (2021), e-mail to Norio Ota: n-otajitaku@nifty.com ]
{"title":"Void-Defect Induced Magnetism and Structure Change of Carbon Materials -Ⅰ: Graphene Nano Ribbon","authors":"N. Ota, L. Nemes","doi":"10.3379/MSJMAG.2103R005","DOIUrl":"https://doi.org/10.3379/MSJMAG.2103R005","url":null,"abstract":"Void-defect is a possible origin of ferromagnetic-like feature of pure carbon material. Applying density functional theory to void-defect induced graphene-nano-ribbon (GNR), a detailed relationship between multiple-spin-state and structure change was studied. An equilateral triangle of an initial void having six electrons is distorted to isosceles triangle by re-bonding carbon atoms. Among possible spin-states of Sz=0/2, 2/2, 4/2 and 6/2, the most stable state was Sz=2/2. The case of Sz=4/2 is remarkable that initial flat ribbon turned to three dimensionally curled one having highly polarized spin configuration at ribbon edges. Total energy of Sz=4/2 was very close to that of Sz=2/2, which suggests coexistence of flat ribbon and curled ribbon. As a model of three dimensional graphite, bi-layered AB stacked GNR was analyzed for cases of different void position of α-site and β-site. Spin distribution was limited to the surface layer, nothing to the back layer. Distorted void triangle show 60degree clockwise rotation from αto β-site, which was consistent with experimental observation using the scanning tunneling microscope. This study revealed that void-defect in GNR induces unusual polarized spin state, different with usual ferromagnetic one. [ To be published on Journal of the Magnetics Society of Japan (2021), e-mail to Norio Ota: n-otajitaku@nifty.com ]","PeriodicalId":36791,"journal":{"name":"Journal of the Magnetics Society of Japan","volume":"39 1","pages":"30-36"},"PeriodicalIF":0.0,"publicationDate":"2021-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89652661","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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