共查询到20条相似文献,搜索用时 31 毫秒
1.
N.V. Rama Rao R. Gopalan M. Manivel Raja V. Chandrasekaran D. Chakravarty R. Sundaresan R. Ranganathan K. Hono 《Journal of magnetism and magnetic materials》2007
SmCo5+x wt% Fe (x=0, 5 and 10) nanocomposite powders were synthesized by mechanical milling and were consolidated into bulk shape by spark plasma sintering (SPS) technique. The evolution of structure and magnetic properties were systematically investigated in milled powders as well as in SPS samples. A maximum coercivity of 8.9 kOe was achieved in spark plasma sintered SmCo5+5 wt% Fe sample. The exchange spring interaction between the hard and soft magnetic phases was evaluated using δM–H measurements and the analysis revealed that the SPS sample containing 5 wt% Fe had a stronger exchange coupling between the magnetic phases than that of the sample with10 wt% Fe. 相似文献
2.
The magnetization reversal behaviour for SmCo6.8Zr0.2 and SmCo6.8Zr0.2/α-(Fe,Co) nanocrystalline magnets at low temperature
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This paper reports that the SmCo 6.8 Zr 0.2 nanocrystalline permanent magnets and SmCo 6.8 Zr 0.2 /α-(Fe,Co) nanocomposite permanent magnets are successfully produced by mechanical alloying and subsequently annealing at 700 C for 10 minutes.The x-ray diffraction results show that the phase structure of SmCo 6.8 Zr 0.2 nanocrystalline permanent magnets is composed of SmCo 7 phase and SmCo 6.8 Zr 0.2 /α-(Fe,Co) nanocomposite permanent magnets is composed of SmCo 7 and α-(Fe,Co) phases.The mechanism of magnetization reversal is mainly controlled by inhomogeneous domain wall pinning in SmCo 6.8 Zr 0.2 and SmCo 6.8 Zr 0.2 /α-(Fe,Co) magnets.The inter-grain exchange interaction at low temperature is investigated,which shows that the inter-grain exchange interaction of SmCo 6.8 Zr 0.2 /α-(Fe,Co) magnets increases greatly by the decrease of the measured temperature.According to Δm irr-H/H cj,Δm rev-H/H cj and χ irr-H/H cj curves at room temperature and 100 K,the changes of irreversible and reversible magnetization behaviours of SmCo 6.8 Zr 0.2 and SmCo 6.8 Zr 0.2 /α-(Fe,Co) magnets with the decreasing temperature are analysed in detail.The magnetic viscosity and the activation volume of SmCo 6.8 Zr 0.2 and SmCo 6.8 Zr 0.2 /α-(Fe,Co) magnets at different temperatures are also studied. 相似文献
3.
Fabrication and Characterization of SmCo5/Fe65Co35 and SmCo5/Fe Composite Spring Exchange Magnets
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SmCo5/Fe65Co35 and SmCo5/Fe spring exchange magnets are fabricated by dc magnetron sputtering on MgO substrates and 100-nm-thick Si3N4 membranes, respectively. The base pressure of sputtering chamber is kept below 10^-7 Tort, and Ar pressure is 3 to 8mTorr. The samples are characterized by an x-ray diffractometer, a superconducting quantum interference magnetometer, and high resolution magnetic soft x-ray microscopy. We obtain the complete exchange coupling and single phase behaviour of composite magnets. The (BH)max value achieved is 28.8 MGOe. 相似文献
4.
Toru Asahi Isao Koizumi Yuta Kikuchi Masahiro Yoshino Atsushi Sugiyama Jiro Hokkyo Tetsuya Osaka 《Journal of magnetism and magnetic materials》2008
An SmCo5 alloy is a promising candidate for ultra-high density magnetic recording media because of its strong uniaxial magnetocrystalline anisotropy, whose constant, Ku, is more than 1.1×108 erg/cm3. Recently, we successfully obtained high perpendicular magnetic anisotropy for a sputter-deposited SmCo5 thin film by introducing a Cu/Ti dual underlayer. However, it is necessary to improve magnetic properties and read/write (R/W) characteristics for applying SmCo5 thin films to perpendicular magnetic recording media. In this study, we focused on reduction of magnetic domain size and change of a magnetization reversal process of SmCo5 perpendicular magnetic thin films by introducing carbon (C) atoms into the constituent Cu underlayer. The magnetic domain size became small and the ratio of coercivity (Hc) against magnetic anisotropy (Hk) which is an index of the magnetization reversal process was increased by adding C atoms. We also evaluated the R/W characteristics of SmCo5 double-layered media including C atoms. The medium noise was decreased and signal-to-noise ratio increased by introducing the C. The addition of C into the Cu underlayer is effective for changing the magnetization reversal process, reducing medium noise and increasing SNR. 相似文献
5.
Toru Asahi Yuko Egawa Atsushi Sugiyama Takanori Kiya Kazuhiro Ouchi 《Journal of magnetism and magnetic materials》2010,322(23):3784-3788
SmCo5 alloy is a promising candidate for ultra-high-density perpendicular magnetic recording (PMR) media because of its high uniaxial magnetocrystalline anisotropy Ku of more than 1.1×108 erg/cm3. Previously, we successfully achieved high Ku in a sputter-deposited SmCo5 thin film by introducing a Cu/Ti dual underlayer. However, in order to apply the SmCo5 films to practical PMR media, it is necessary to decrease medium noise. A granulated magnetic film comprising of small and magnetically decoupled grains is effective in reducing the medium noise. In this paper, we have proposed a new granular film that is fabricated by partial thermodiffusion of Cu between the Sm-Co continuous layer and the Cu underlayer, which is granulated using compositional segregation caused by the addition of Ta2O5. We have analyzed the magnetic properties, magnetic domain size, and magnetization reversal process of the proposed SmCo5 film. The magnetic domain size decreased and the magnetization reversal process changed from the magnetic-wall-motion mode to a coherent rotation mode to some extent on isolation of magnetic grains. The read/write characteristics of granulated SmCo5 double-layered media were also evaluated. The medium noise decreased and the signal-to-noise ratio increased for the granulated double-layered (PMR) medium. 相似文献
6.
Dapeng Wang Narayan Poudyal Chuanbing Rong Ying Zhang M.J. Kramer J. Ping Liu 《Journal of magnetism and magnetic materials》2012
Nanoscale hybrid magnets containing SmCo5 and Nd2Fe14B hard magnetic phases have been produced via a novel “in-one-pot” processing route. The grain size of the processed bulk composite materials is controlled below 20 nm. The refinement of the nanoscale morphology leads to effective inter-phase exchange coupling that results in single-phase like magnetic properties. Energy product of 14 MGOe was obtained in the isotropic nanocomposite magnets at room temperature. At elevated temperatures, the hybrid magnets have greatly improved thermal stability compared to the Nd2Fe14B single-phase counterpart and have substantially increased magnetization and energy products compared to the single-phase SmCo5 counterpart. 相似文献
7.
H. Oesterreicher 《Applied Physics A: Materials Science & Processing》1978,15(4):341-354
Crystallographically partly randomized materials with high magnetic anisotropy exhibit anisotropy and exchange fluctuations.
Possibly the most dramatic consequence of these interaction fluctuations is the presence of giant intrinsic magnetic hardness
observed, especially at cryogenic temperatures. This magnetic hardness (resistance to demagnetization) is anintrinsic solid state property, quite in contrast with hardness in technologically important materials based on the presence of fine particles or precipitate
phases. It introduces rather a further variety in the phenomenology of interaction fluctuation materials such as spin glasses,
representing the extreme case of high anisotropy and high moment concentrations. In this paper the phenomenon of strong intrinsic
magnetic hardness is reviewed, and some new experimental data are presented for homogeneous pseudobinary regions of composition
on the basis of such compounds as SmNi5, SmCu5, SmCo5, TbFe2 and others. Magnetic hardness in some of these cases reaches the highest values found so far for any class of materials.
For instance, maximum values of coercive force of aboutH
c=230 kOe are observed for SmCo5−xNix. Even higher values are extrapolated in other cases. Maximum values ofH
c are observed in materials with ordering temperatures of order 60–200 K. A strong temperature and a weaker time dependence
ofH
c is observed and discussed on the basis of theories involving thermal activation of domain propagation. Comparisons are drawn
with effects generally observed in magnetically hard materials, and the relationship of intrinsic magnetic hardness to technologically
interesting materials is discussed. Tentative conclusions as to the details of the origins of giant intrinsic magnetic hardness
are drawn and areas of future interest are indicated.
This study was supported by a grant from the National Science Foundation. 相似文献
8.
We have investigated the influence of composition and annealing conditions on the magnetic properties and microstructural features of SmCox films that were prepared by sputtering and subsequent annealing. A huge in-plane coercivity of 5.6 T was obtained from an optimally annealed Sm–Co film, which was attributed to the nanometer sized polycrystalline microstructure of the highly anisotropic SmCo5 phase. Although a high density of planar defects were observed in the films that were annealed at high temperatures, they did not act as strong pinning sites for domain wall motion. The effect of Cu on [SmCo4.5(9 nm)/Cu(xnm)]10 multilayer thin films was also studied. An appropriate Cu content increased the coercivity. 相似文献
9.
P. Saravanan S.V. KamatB. Sreedhar 《Journal of magnetism and magnetic materials》2012,324(6):1201-1204
In this study, we investigated the microstructure, phase evolution and magnetic properties of nanogranular films of Sm-Co compounds processed by the sol-gel method. By controlling the compositional ratio of Sm:Co precursor concentration, nanogranular films consisting of three distinct hard magnetic phases namely, Sm2Co7, SmCo5 and Sm2Co17 with coercivity values of 1.78, 2.94 and 2.12 kOe, respectively, were obtained through this technique. 相似文献
10.
《Journal of magnetism and magnetic materials》2001,233(3):257-273
The magnetic and microstructural properties and magnetic domain configuration of exchange-spring model bilayer samples based on L10-type magnetically-hard CoPt and magnetically soft Co were examined and analyzed. Bilayers of varying thicknesses and annealing conditions were examined with room-temperature and elevated-temperature SQUID magnetometry, X-ray diffraction, transmission electron microscopy and magnetic force microscopy. While lower-temperature (300°C ⩽T⩽400°C) annealing treatments produced little change in the domain configuration, it did produce subtle change in the microstructure and a noticeable increase in the degree of exchange coupling of the bilayers. Higher-temperature (T=550°C) annealing treatments produced profound changes in all parameters: the magnetic reversal behavior, the remanence ratio and the magnetic domain configuration. These changes were accompanied by distinct changes in the bilayer phase constitution and proportions of hard and soft phases produced by interdiffusion of the Co and CoPt layers which altered the overall anisotropy and associated magnetic behavior of the system. To support these conjectures micromagnetic modeling of different conditions of the bilayer properties showed that changing the relative proportions of the hard and soft layers could indeed lead to changes in the magnetic behavior similar to those observed in the experimental systems. Both the experimental and modeling-derived results of this work demonstrate that the bulk technical properties of a hard/soft magnetic nanocomposite material depend on the relative proportions of the phases present, the degree of exchange coupling across the interface between those phases as well as on the physical and magnetic properties of those phases. Changing the physical properties of the phases in systematic ways allows the magnetic properties of the ensemble to be tailored. 相似文献
11.
Chun Feng Ning Li Shuai Li Qianming Huo Minghua Li Qian Zhan Baohe H. Li Jinhua Yin Yong Jiang Guanghua Yu 《Applied Physics A: Materials Science & Processing》2012,106(1):125-129
High thermal stability and tunable magnetic exchange interaction (MEI) in SmCo materials have been the critical problem in
applications to magnetic recording media and nanocomposite permanent magnets. We constructed SmCo films with a high thermal
stability and tunable MEI by controlling the phase transformation through properly increasing the Sm concentration (20.5–37.7
at.%) and controlling the annealing process. Microstructure studies show that the SmCo5 phases ensure that the film has a high thermal stability. Moreover, we manipulated the MEI in the film with non-magnetic
precipitated SmCo2 particles in the vicinity of SmCo5 particles. These results provide a novel way to tune the MEI in SmCo materials while maintaining a high thermal stability. 相似文献
12.
Weiming Cheng Wenwu Liu Xiao Wang Yifan Dai Xiaomin Cheng Xiangshui Miao 《Journal of magnetism and magnetic materials》2012
A new seed layer TiW is proposed for SmCo5 films with perpendicular magnetic anisotropy. The influence of a TiW seed layer on the microstructure and the surface morphology of Cu underlayer are studied. The grain size and surface roughness dependence of Cu underlayer on the thickness and the annealing of the TiW seed layer are also investigated. The improvement in the perpendicular magnetic properties of SmCo5 film from the TiW seed layer is approved. The results show that a 5 nm Ti3W7 seed layer improves the microstructure and surface morphology of Cu underlayer, and significantly improves the perpendicular magnetic properties of SmCo5 film. The diffusion barrier and a high melting point of the TiW seed layer are regarded as the physical mechanism of the improvement for SmCo5 film with perpendicular magnetic anisotropy. 相似文献
13.
Juliane Thielsch Dietrich Hinz Ludwig Schultz Oliver Gutfleisch 《Journal of magnetism and magnetic materials》2010,322(20):3208-3213
Textured composite samples consisting of Nd13.6Fe73.6Ga0.6Co6.6B5.6 (MQU-F™) and micron-sized Fe particles with weight ratios from 100:0 to 70:30 have been prepared by hot deformation. Microstructure studies revealed a layered structure of both phases with the layer normal parallel to the pressing direction. Magnetic measurements showed single-phase hysteresis curves for all samples when measured along the pressing direction, which is also the easy axis of magnetization. Coercivity decreased drastically from 1.32 T for pure NdFeB samples to 0.154 T for a sample with 30 wt% Fe. Magneto-optical Kerr microscopy with a digitally enhanced imaging technique has been used to examine the evolution of magnetic domains in the hard and soft phase during demagnetizing a sample consisting of 70 wt% NdFeB and 30 wt% Fe. It is shown that demagnetization takes place via domain rearrangements within the soft phase, which lead to and support the nucleation of reversed interaction domains at phase boundaries. Also nucleation of interaction domains within the hard magnetic phase could be revealed. 相似文献
14.
P. Saravanan A.N. Sharma V. Chandrasekaran 《Journal of magnetism and magnetic materials》2009,321(19):3138-3143
Highly anisotropic SmCo5 nanocrystalline powders with grain size in the range 5-20 nm were processed through surfactant and magnetic field-assisted milling. The SmCo5 nanocrystalline powders so obtained by this method possess unusual characteristics such as reduction in particle size, platelet-structure and high remanence values. A possible mechanism for achieving remanence enhancement with the surfactant-coated SmCo5 powders has been discussed. Besides, the resin-bonded magnets processed with the surfactant-coated SmCo5 powders showed relatively higher density, induction remanence and energy product with strong anisotropic behavior than those of the magnets processed with the conventionally milled SmCo5 powders. Maximum values of Hci (16 kOe), Br (4.66 kG) and (BH)max (5.5 MG Oe) were achieved for the resin-bonded magnets processed with the surfactant-coated powders. 相似文献
15.
采用直流溅射和热处理技术制备了两个各向同性的纳米结构Fe-Pt永磁合金薄膜系列,并研究了它们的结构和磁性.研究表明,在富Fe双相纳米结构Fe-Pt永磁合金薄膜中,仅由硬磁的FePt相与软磁的Fe3Pt相组成;在同一系列中,随Fe层厚度的增加,饱和磁极化强度和剩磁明显增大.由Kelly-Henkel图研究指出,在上述Fe-Pt纳米结构永磁合金薄膜中,磁相互作用主要由近邻纳米晶粒间的铁磁交换相互作用控制.
关键词:
磁性薄膜
纳米结构
矫顽力 相似文献
16.
X.Y. Xiong C.B. RongS. Rubanov Y. ZhangJ.P. Liu 《Journal of magnetism and magnetic materials》2011,323(22):2855-2858
The microstructure and compositions of the bulk nanocomposite SmCo/Fe permanent magnet were studied using transmission electron microscopy and 3-dimensional atom probe techniques. The excellent magnetic properties were related to the uniform nanocomposite structure with nanometer α-Fe particles uniformly distributed in the SmCo phase matrix. The α-Fe phase contained ∼26 at% Co, and the SmCo phase contained ∼19 at% Fe, confirming that the interdiffusion of Fe and Co atoms between the two phases occurred. The formation of the α-Fe(Co) phase explained why the saturation magnetization of the nanocomposite permanent magnet was higher than that expected from the original pure α-Fe and SmCo5 powders, which enhanced further the maximum energy product of the nanocomposite permanent magnet. 相似文献
17.
Ersin Kantar 《哲学杂志》2013,93(6):431-450
AbstractIn this paper, a theoretical approach to evaluate the hysteresis behaviours of Ising-type segmented nanowire (ISN) comprising magnetic and diluted magnetic segments is defined. The dependency to the system parameters are calculated for optimising their performance in applications like magnetic sensors or recording media. The effects of the composition (p) and temperature (T) as well as crystal field on the hysteresis behaviours are investigated in detail. We studied the effect of the segment dimensions obtained from the exchange interactions. The coercivity (HC) and remanence (Mr) of the ISN are derived from hysteresis loops. The phase diagrams are presented in the different planes as function of HC and Mr to investigate the magnetic characteristics of the ISN. Under certain conditions, namely p = 0 and JD = 0, we also examined the effect of temperature on the nanowire with magnetic and non-magnetic segments. The distinct hysteresis properties and soft/hard the magnetic characteristics depending upon these factors are observed. We found that the magnetic hardness decreases case as the temperatures increase as well as p and crystal field (Δ) decrease. Moreover, when the p increase and Δ decrease the triple hysteresis loop behaviour occurs in the system. Comparisons between the observed theoretical results and some experimental works of nanowire with hysteresis behaviours are made and a very good agreement is obtained. 相似文献
18.
《Journal of magnetism and magnetic materials》2001,234(3):395-400
The phase transformation and magnetic properties of SmCo7−xBx (x=0, 0.2, 0.5 and 1) alloys prepared by mechanical alloying have been investigated systematically. The coercivities of the alloys without B increase with increasing annealing temperature, as a consequence of complete crystallization of TbCu7-type phase. The substitution of B for Co is favorable to the formation of Th2Zn17- and CaCu5-type phases when annealed at 650°C, accompanied by the enhancement of the coercivities. Increasing the annealing temperature causes the formation of soft magnetic phase Sm2Co14B in the B-substituted alloys. In the alloys with x=0.5 and 1 annealed at 850°C, the major phase is Sm2Co14B, which degrades the magnetic properties sharply. A remanence enhancement has been observed in the SmCo7−xBx alloys due to the exchange coupling of the nanoscale structure. 相似文献
19.
A systematic study on Ni-W alloy underlayers has shown that a highly textured (2 1 1)-Ni4W can be formed after deposition at room temperature. Highly textured (0 0 0 1)-SmCo5 with a high out-of-plane coercivity (over 10 kOe) and large perpendicular anisotropy can be obtained after deposition on the (2 2 1)-Ni4W underlayer probably due to a small mismatch between (2 2 1)-Ni4W and (0 0 0 1)-SmCo5. Our study indicates that the surface roughness of the underlayers also plays a crucial role, that a smooth surface is favorable for a good crystallinity and high coercivity of SmCo5. Moreover, we found that a highly textured Ni-(1 1 1) can be obtained on the top of the (2 1 1)-textured Ni4W. The film structure of SmCo5/Ni/Ni4W may be interesting as the hard/soft double-layered film for perpendicular magnetic recording or for other applications after a further development. 相似文献
20.
Zambano A. J. Oguchi H. Takeuchi I. Liu J. P. Lofland S. E. Bendersky L. A. Liu Y. Wang Z. L. 《Applied Physics A: Materials Science & Processing》2011,103(4):1183-1187
We use magnetic thin film hard/non/soft-magnetic trilayer systems to probe the nature of the hard–soft phase interaction and
the role played by dipolar fields in one-dimensional (d) magnetic systems. We have systematically investigated six wedge samples where the thickness of a Cu spacer layer (t
Cu) was gradually changed to create a varying interfacial effect on the interaction between a CoPt hard layer and a Fe soft
layer. Magneto-optical Kerr effect was used to obtain the magnetization loops at 28 points on each sample, and the nucleation
field (H
N
) as a function of t
Cu was employed to characterize the layer interaction as a function of t
Cu. H
N
(t
Cu) show a RKKY oscillatory behavior in addition to a non-negligible dipolar contribution, which had an exponential dependence.
The dipolar term, which cannot be always neglected, is affected by the interface roughness and also by the CoPt crystallinity.
Therefore, we cannot always consider exchange coupling to be the dominant interaction in one-d hard–soft magnetic bilayer systems, particularly, during magnetic reversal. 相似文献