Challenges and recent developments associated with writability issues in high-anisotropy perpendicular recording media are reviewed. The writing field is limited by the high coercivity caused by the high anisotropy. S...Challenges and recent developments associated with writability issues in high-anisotropy perpendicular recording media are reviewed. The writing field is limited by the high coercivity caused by the high anisotropy. Some new alterna- tives are proposed to solve the writability issues, including texture-tilting-assisted, domain-wall-assisted, energy-assisted magnetic recording technologies, and so on, In addition, we propose new alternatives for the next-generation of magnetic recording media.展开更多
The magnetic properties of exchange coupled composite (ECC) media that are composed of perpendicular magnetic recording media FePt MgO and two kinds of soft layers have been studied by using an x-ray diffractometer,...The magnetic properties of exchange coupled composite (ECC) media that are composed of perpendicular magnetic recording media FePt MgO and two kinds of soft layers have been studied by using an x-ray diffractometer, a polar Kerr magneto-optical system (PMOKE) and a vibrating sample magnetometer (VSM). The results show that ECC media can reduce the coercivities of perpendicular magnetic recording media FePt-MgO. The ECC media with granular-type soft layers have weaker exchange couplings between magnetic grains and the magnetization process, for ECC media of this kind mainly follow the Stoner Wohlfarth model.展开更多
(FePt/Ag)n nano-multilayers were deposited on MgO (100) single crystal with laser ablation and then subjected to annealing. FePt L1o grains with (001) texture and thus a large perpendicular magnetic anisotropy constan...(FePt/Ag)n nano-multilayers were deposited on MgO (100) single crystal with laser ablation and then subjected to annealing. FePt L1o grains with (001) texture and thus a large perpendicular magnetic anisotropy constant Ku of the order of 106 J/m3 were formed. A thick Ag layer is found to be favorable for decreasing the dispersion of the easy axis for magnetization. The measurement of time decay of magnetization gave rise to a small activation volume of the order of 10-25m3, showing the promising of being the recording medium for future high density perpendicular recording.展开更多
The studies were made on the preparation processes of the rare earth metal and alloy target materials and their characterization. In this work the rare earth metals were prepared by electrolysis of the oxide in molten...The studies were made on the preparation processes of the rare earth metal and alloy target materials and their characterization. In this work the rare earth metals were prepared by electrolysis of the oxide in molten salt for Nd metal and metallothermic reduction of the fluorides for Gd, Tb, Dy metals. After vacuum refining and distillation purification these rare earth metals were used for manufacturing the element targets, mosaic targets and as the starting materials of preparing the rare earth-transition metal (RE-TM) alloy targets. The four kinds of Dy-FeCo, NdDy-FeCo, Tb-FeCo and GdTb-FeCo alloy targets with diameter of 100 mm and thickness of 3 mm were prepared using powder metallurgical technique. The oxygen content and microstructure of the prepared RE-TM cast alloys and sintered targets were analyzed. The features and requirements of the RE-TM alloy sputtering target materials were also discussed.展开更多
Single phase Fe 5C 2 intermetallic compound was prepared by mechanical alloying method. The phase and crystal structure of sample were analyzed with X ray differaction spectrum. The decomposing temperature of the F...Single phase Fe 5C 2 intermetallic compound was prepared by mechanical alloying method. The phase and crystal structure of sample were analyzed with X ray differaction spectrum. The decomposing temperature of the Fe 5C 2 compound is 596.4℃ determined by the DSC curve. It is further shown that the size of nanometer crystal grain is an important condition for carrying out the solid state reaction at room temperature and normal pressure.展开更多
A reduction in the track width of magnetic recording systems results in a welcome increase in Areal Density(AD),but can severely deteriorate system performance in the unfortunate appearance of extreme Inter-Track Inte...A reduction in the track width of magnetic recording systems results in a welcome increase in Areal Density(AD),but can severely deteriorate system performance in the unfortunate appearance of extreme Inter-Track Interference(ITI).The effect of severe ITI may be mitigated by using coding schemes.In this paper,therefore,we present a rate-5/62-Dimensional(2D)modulation code based on a proposed Single-Reader/Two-track Reading(SRTR)technique to cope with this serious problem in staggered Bit-Pattemed Magnetic Recording(BPMR)systems.We then evaluate the Bit-Error Rate(BER)performance of the proposed system in the presence of media noises,e.g.,position and size fluctuations.Our simulation results indicate that,at the same User Density(UD),the proposed system performs better than an uncoded system by about 1.0 dB at the BER of 105 and is also superior to the conventional recording system.展开更多
In the present work, a series of Ta/Ru/Co- 23 at%Pt thin films with varied Ru underlayer thicknesses were fabricated by magnetron sputtering. All of the films show c-axis preferred orientation perpendicular to the fil...In the present work, a series of Ta/Ru/Co- 23 at%Pt thin films with varied Ru underlayer thicknesses were fabricated by magnetron sputtering. All of the films show c-axis preferred orientation perpendicular to the film surface. The drop of c/a ratio and lattice expansion of Co- Pt layer with the increase in Ru underlayer thickness was revealed by X-ray diffraction (XRD). The coercivity of the Ta/Ru/Co-Pt thin films increases drastically with Ru underlayer thickness increasing, due to the enhancement of effective magneto-crystalline anisotropy constant and exchange decoupling of magnetic nano-grains. The enhancement of effective magneto-crystalline anisotropy constant is ascribed to the lattice deformation of Co-Pt layer by mismatching the Ru layer and Co-Pt surface. Moreover, the exchange decoupling of magnetic nanograins is attributed to the further isolation of magnetic nano-grains.展开更多
In this paper, ternary Co-Pt-P thin films were prepared by Co-P chips pasted on the cobalt target. The structure magnetron sputtering with platinum and home-made and magnetic properties were investigated by X-ray diff...In this paper, ternary Co-Pt-P thin films were prepared by Co-P chips pasted on the cobalt target. The structure magnetron sputtering with platinum and home-made and magnetic properties were investigated by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM), respectively. With increasing phosphor content, the coercivities of Co-12 at.% Pt-P films increase from 1034 to 1525 Oe owing to the exchange decoupling among magnetic grains. The decrease of inter-granular exchange coupling was confirmed by delta-M curve measurement and magnetic force microscopy (MFM). Transmission electronic microscopy (TEM) with nano- beam composition analysis shows that phosphor segregated at cobalt-based grain boundaries is responsible for the exchange decoupling. It is thus suggested that the phosphor addition is effective to tune the exchange coupling of magnetic grains, particularly for perpendicular recording media.展开更多
A series of hexagonal close-packed (HCP) Co-W thin films were deposited by sputtering on surface oxidized silicon substrates at 300 ℃. A linear dependency of saturation magnetization (Ms) on W content was found u...A series of hexagonal close-packed (HCP) Co-W thin films were deposited by sputtering on surface oxidized silicon substrates at 300 ℃. A linear dependency of saturation magnetization (Ms) on W content was found up to about 9 at. pct W, and then it underwent an increased Ms vs. W content curve as compared to the initial linear dependency. The thermal magnetization technique was used to confirm that the ino creased Ms behaviour is correlated to the phase separation of the Co-W thin films. The phase separation behaviour was also found to be dependent on W content and the reason was discussed in detail. Finally an interesting composition range was suggested to be about 13 at. pct-17 at. pct W for the Co-W thin films, in which they exhibit much higher magnetic anisotropy energy than Co-Cr thin films and improved phase separation.展开更多
The microstructure and magnetic properties of Co/Cr bilayer films were examined before and after postdeposition annealing by using transmission electron microscopy (TEM), X-ray diffraction (XRD) technique and vibr...The microstructure and magnetic properties of Co/Cr bilayer films were examined before and after postdeposition annealing by using transmission electron microscopy (TEM), X-ray diffraction (XRD) technique and vibrating sample magnetometer (VSM). A model of grain boundary (GB) Cr-rich phase growth involving GB diffusion derived from the Cr underlayer was proposed to elucidate the kinetics of the paramagnetic Cr-rich phase growth along Co GBs within the Co layer. The correlation of the GB Cr-rich phase formation with the magnetic Co grain isolation and accordingly, improvement of magnetic properties was experimentally investigated and discussed in detail. Our analysis results are well consistent with previous micromagnetic simulations on the improvement of magnetic properties by the magnetic grain isolation. The results provide some insights into the processing-structure-property relationships of the Co/Cr bilayer films, and thus suggest that the magnetic grain isolation be feasible not only in longitudinal recording media, but also be effective in tuning the exchange coupling of magnetic grains in perpendicular recording media via the GB diffusion from underlayer and/or overlayer.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51025101,51101095,and 11274214)the Program for Changjiang Scholars and Innovative Research Team in University,China(Grant No.IRT1156)+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20121404130001)the Shanxi Province Foundations,China(Grant Nos.2011021021-1,[2012]10,and[2013]9)
文摘Challenges and recent developments associated with writability issues in high-anisotropy perpendicular recording media are reviewed. The writing field is limited by the high coercivity caused by the high anisotropy. Some new alterna- tives are proposed to solve the writability issues, including texture-tilting-assisted, domain-wall-assisted, energy-assisted magnetic recording technologies, and so on, In addition, we propose new alternatives for the next-generation of magnetic recording media.
基金Project supported by the Japanese Storage Research Consortium (SRC)the Grant-in-Aid for Scientific Research (A) of the Japanese Ministry of Education, Culture, Sports, Science and Technology (Grant No 14205049)
文摘The magnetic properties of exchange coupled composite (ECC) media that are composed of perpendicular magnetic recording media FePt MgO and two kinds of soft layers have been studied by using an x-ray diffractometer, a polar Kerr magneto-optical system (PMOKE) and a vibrating sample magnetometer (VSM). The results show that ECC media can reduce the coercivities of perpendicular magnetic recording media FePt-MgO. The ECC media with granular-type soft layers have weaker exchange couplings between magnetic grains and the magnetization process, for ECC media of this kind mainly follow the Stoner Wohlfarth model.
基金The present work has been partially supported by the Japanese Storage Research ConsortiumSupport by Beijing Science and Technology Nova Project(Grant No.H020821290120)is also appreciated.
文摘(FePt/Ag)n nano-multilayers were deposited on MgO (100) single crystal with laser ablation and then subjected to annealing. FePt L1o grains with (001) texture and thus a large perpendicular magnetic anisotropy constant Ku of the order of 106 J/m3 were formed. A thick Ag layer is found to be favorable for decreasing the dispersion of the easy axis for magnetization. The measurement of time decay of magnetization gave rise to a small activation volume of the order of 10-25m3, showing the promising of being the recording medium for future high density perpendicular recording.
基金Former the Ministry of Metallurgical Industry of China (BJ95-06-01)
文摘The studies were made on the preparation processes of the rare earth metal and alloy target materials and their characterization. In this work the rare earth metals were prepared by electrolysis of the oxide in molten salt for Nd metal and metallothermic reduction of the fluorides for Gd, Tb, Dy metals. After vacuum refining and distillation purification these rare earth metals were used for manufacturing the element targets, mosaic targets and as the starting materials of preparing the rare earth-transition metal (RE-TM) alloy targets. The four kinds of Dy-FeCo, NdDy-FeCo, Tb-FeCo and GdTb-FeCo alloy targets with diameter of 100 mm and thickness of 3 mm were prepared using powder metallurgical technique. The oxygen content and microstructure of the prepared RE-TM cast alloys and sintered targets were analyzed. The features and requirements of the RE-TM alloy sputtering target materials were also discussed.
文摘Single phase Fe 5C 2 intermetallic compound was prepared by mechanical alloying method. The phase and crystal structure of sample were analyzed with X ray differaction spectrum. The decomposing temperature of the Fe 5C 2 compound is 596.4℃ determined by the DSC curve. It is further shown that the size of nanometer crystal grain is an important condition for carrying out the solid state reaction at room temperature and normal pressure.
基金This work was patially supported by the Thailand Research Fund under the grant number RSA6080051,College of Advanced Manufacturing Innovation(AMD),and King Mongkut's Institute of Technology Ladkrabang(KMIIL),Thailand.
文摘A reduction in the track width of magnetic recording systems results in a welcome increase in Areal Density(AD),but can severely deteriorate system performance in the unfortunate appearance of extreme Inter-Track Interference(ITI).The effect of severe ITI may be mitigated by using coding schemes.In this paper,therefore,we present a rate-5/62-Dimensional(2D)modulation code based on a proposed Single-Reader/Two-track Reading(SRTR)technique to cope with this serious problem in staggered Bit-Pattemed Magnetic Recording(BPMR)systems.We then evaluate the Bit-Error Rate(BER)performance of the proposed system in the presence of media noises,e.g.,position and size fluctuations.Our simulation results indicate that,at the same User Density(UD),the proposed system performs better than an uncoded system by about 1.0 dB at the BER of 105 and is also superior to the conventional recording system.
基金financially supported by the National Natural Science Foundation of China(No.51525101)the Fundamental Research Funds for the Central Universities(Nos.120309001 and 140904002)
文摘In the present work, a series of Ta/Ru/Co- 23 at%Pt thin films with varied Ru underlayer thicknesses were fabricated by magnetron sputtering. All of the films show c-axis preferred orientation perpendicular to the film surface. The drop of c/a ratio and lattice expansion of Co- Pt layer with the increase in Ru underlayer thickness was revealed by X-ray diffraction (XRD). The coercivity of the Ta/Ru/Co-Pt thin films increases drastically with Ru underlayer thickness increasing, due to the enhancement of effective magneto-crystalline anisotropy constant and exchange decoupling of magnetic nano-grains. The enhancement of effective magneto-crystalline anisotropy constant is ascribed to the lattice deformation of Co-Pt layer by mismatching the Ru layer and Co-Pt surface. Moreover, the exchange decoupling of magnetic nanograins is attributed to the further isolation of magnetic nano-grains.
基金supported by the Program for New Century Excellent Talents in University (No. NCET-09-0272)the Liaoning Program for Excellent Talents in University (No. 2009R23)One of authors, B. Yang appreciates Northeastern University Research Foundation for Excellent Doctor Candidates (No. 200904)
文摘In this paper, ternary Co-Pt-P thin films were prepared by Co-P chips pasted on the cobalt target. The structure magnetron sputtering with platinum and home-made and magnetic properties were investigated by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM), respectively. With increasing phosphor content, the coercivities of Co-12 at.% Pt-P films increase from 1034 to 1525 Oe owing to the exchange decoupling among magnetic grains. The decrease of inter-granular exchange coupling was confirmed by delta-M curve measurement and magnetic force microscopy (MFM). Transmission electronic microscopy (TEM) with nano- beam composition analysis shows that phosphor segregated at cobalt-based grain boundaries is responsible for the exchange decoupling. It is thus suggested that the phosphor addition is effective to tune the exchange coupling of magnetic grains, particularly for perpendicular recording media.
基金supported by the National Natural Science Foundation of China(No50671020)Ministry of Education of China (No108039)
文摘A series of hexagonal close-packed (HCP) Co-W thin films were deposited by sputtering on surface oxidized silicon substrates at 300 ℃. A linear dependency of saturation magnetization (Ms) on W content was found up to about 9 at. pct W, and then it underwent an increased Ms vs. W content curve as compared to the initial linear dependency. The thermal magnetization technique was used to confirm that the ino creased Ms behaviour is correlated to the phase separation of the Co-W thin films. The phase separation behaviour was also found to be dependent on W content and the reason was discussed in detail. Finally an interesting composition range was suggested to be about 13 at. pct-17 at. pct W for the Co-W thin films, in which they exhibit much higher magnetic anisotropy energy than Co-Cr thin films and improved phase separation.
基金supported by the National Natural Sci-ence Foundation of China (No 50671020)the Chinese Ministry of Education (Nos 108039 and IRT0713)
文摘The microstructure and magnetic properties of Co/Cr bilayer films were examined before and after postdeposition annealing by using transmission electron microscopy (TEM), X-ray diffraction (XRD) technique and vibrating sample magnetometer (VSM). A model of grain boundary (GB) Cr-rich phase growth involving GB diffusion derived from the Cr underlayer was proposed to elucidate the kinetics of the paramagnetic Cr-rich phase growth along Co GBs within the Co layer. The correlation of the GB Cr-rich phase formation with the magnetic Co grain isolation and accordingly, improvement of magnetic properties was experimentally investigated and discussed in detail. Our analysis results are well consistent with previous micromagnetic simulations on the improvement of magnetic properties by the magnetic grain isolation. The results provide some insights into the processing-structure-property relationships of the Co/Cr bilayer films, and thus suggest that the magnetic grain isolation be feasible not only in longitudinal recording media, but also be effective in tuning the exchange coupling of magnetic grains in perpendicular recording media via the GB diffusion from underlayer and/or overlayer.