SmCo/Co多层交换弹性纳米晶复合永磁薄膜的制备和磁耦合研究

利用磁控溅射的方法,在室温条件的Si基片上制备了[SmCo(25nm)/Co(x)]4/SmCo(25 nm)多层交换弹性纳米晶复合永磁薄膜(Co层厚度x=0～10 nm),经过550 ℃/20 min的真空退火处理使薄膜结晶后,进行磁性测试和磁耦合分析.结果表明:SmCo层厚度固定为25 nm时,调整Co层的厚度,从0至10 nm逐渐增加,矫顽力从2270.3 kA·m-1逐渐降低至1040.5 kA·m-1,同时,饱和磁化强度和剩磁随Co层厚度增加逐渐增加,上升了60％.当加入10 nm的Co层后,多层膜的最大磁能积比125 nm的单层SmCo薄膜增加了46％.另外,与SmCo/Co双层交换弹性薄膜在退磁过程中表现的零场附近的软硬磁双相行为相比,SmCo/Co多层交换弹性薄膜表现出单相反转行为,说明体系中的两种磁性层具有更好的磁耦合.经过磁耦合研究发现,当Co软磁层较薄时,薄膜中磁性颗粒以颗粒间交换耦合为主;当软磁层厚度增加时,颗粒间交换耦合减弱,静磁耦合增强,保证了软硬磁相之间的良好磁耦合作用.Co层的加入有效地提高了薄膜的磁性能.     

Crystal structure,microstructure and magnetic properties of SmCo-based films treated by different annealing methods

Effect of conventional thermal annealing(CTA) and rapid recurrent thermal annealing(RRTA) processes on crystal structure,mi-crostructure,and magnetic properties of the SmCo-based films were investigated.The results indicated that the CTA-treated films exhibited poor permanent magnetic properties,and a low intrinsic coercivity of 72.8 kA/m was observed.Wide hysteresis loop was obtained for the RRTA-treated films,providing better permanent magnetic properties.The intrinsic coercivity reached 312.0 kA/m.According to the X-ray diffraction(XRD) and atomic force microscopy(AFM) results,the magnetic properties of the CTA-treated films and RRTA-treated films were found to be correlated with the crystal structure and microstructure,which were strongly determined by the annealing treatment.CTA treatment led to poor crystallization effects for the films,and a rough surface(RMS=3.47 nm and P-V=35.42 nm) and large grain size of 92.7 nm were observed correspondingly.However,the RRTA treatment exhibited great contributions on the crystallization of the films,which is accountable for the smooth surface(RMS=2.047 nm and P-V=16.43 nm) and fine grain size of 60.8 nm.     

Magnetic property and microstructure of SmCo magnetic recording films

Cr/SmCo/Cr thin films with Sm concentration of 37.7 at.% were deposited on glass substrates by magnetron sputtering. Meas-urement of magnetic properties showed that the SmCo film possessed good magnetic anisotropy, a high coercivity of 3019 kA/m and low magnetic exchange coupling. Microstructure analysis showed that crystallized SmCo5 magnetic phase, non-magnetic SmCo2 phase and Sm2Co7 phase co-existed ill the film. The non-magnetic SmCo2 phase might function as isolator of SmCo grains, leading to a decrease of magnetic exchange coupling. Moreover, a Cr2)3 oxide layer which could protect the SmCo layer from oxidation formed at the surface of the Cr cap layer.     

Magnetic properties of SmCo-based permanent magnetic films during 25 to 300 ℃

Magnetic properties of the SmCo-based permanent magnetic films prepared on hot substrate with Mo and Cr underlayer without subsequent annealing process were investigated by vibrating sample magnetometer （VSM）, X-ray diffraction （XRD）, and en- ergy dispersive X-ray spectroscopy （EDS）. The results showed that the film thickness of the SmCo-based films presented complex effect on the intrinsic coercivity Hci. Optimal Hc~ for the films with Mo underlayer, Cr underlayer, and without underlayer was ob- served with different film thicknesses. Furthermore, the monotonous temperature dependence of Hci was found to be strongly corre- lated with the magnetic parameters for the 3.0 μm thick SmCo7 films with Mo underlayer. From 25 to 300 ℃, the Hci decreased from 281.6 to 211.2 kA/m with a temperature coefficient of-0.091%/℃, exhibiting good temperature stability.     

A Study of Two-Phase Nanocrystalline Nd_(8.5)Fe_(75)Co_5Cu_1Zr_3Nb_1B_(6.5)Permanent Magnet

Materialswithenhancedremanentmagneticpo larizationwereinitiallypreparedbyCoehoorn[1] frommelt spunNd3.8Fe77B19.2 ribbonsbyheattreatment .Thesimilarbehaviorwasalsoobservedfrommelt spuntwo phasesamplesofNd2 Fe14 Bandα Fe[2 ] .Themag neticpropertiesofisotropicnanocrystallinetwo phasepermanentsdependsensitivelyonmicrostructuralfea tures,suchasdistributionofmagneticallyhardandsoftphases ,meangrainsize ,particleshapeandgrainboundarytype[3] .Inordertoobtainhighmaximumenergyproduct ,itisnecessaryt…     

Effect of Ti cap layer thickness on microstructures and magnetic properties of Ti/Ni/Ti films

Nanogranular Ti(3 nm)/Ni(30 nm)/Ti(t nm )(t=1,3,5,7,10) films were prepared by facing magnetron sputtering from Ti and Ni onto glass substrates at room temperature.The structural and magnetic properties of films strongly depended on the Ti layer thickness.X-ray diffraction(XRD) patterns of all as-deposited films showed strong FCC Ni(111) peak.Vibrating sample magnetometer(VSM) measurements indicated that the perpendicular coercivity of the Ti(3 nm)/Ni(30 nm)/Ti(3 nm) film reached about 36 kA/m.With the increase of Co layer thickness,coercivity(Hc) first increased and then decreased.The grain size and magnetic clusters slightly increased and the value of roughness(Ra) was smallest at t=3 nm.     

Effect of cobalt substitution on magnetic properties and microstructure of nanocrystalline （NdDyTb）12.3（FeZrNbCu）81.7B6.0 ribbons

Effect of Co substitution and annealing treatment on the formation, magnetic properties and microstructure of (NdOyTb)12.3(FeZrNbCu)81.7CoxB6(x=0-15) ribbons prepared by rapid quenching and subsequent annealing was systematically investi-gated by means of differential scanning calorimeter (DSC), X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM) and vibrating sample magnetometer (VSM). Phase analysis revealed single-phase material. The remanence polarization Jr and maximum en-ergy product (BH)max increased with increasing x from 0 to 12 and then decreased for x=lS. The intrinsic coercivity Hci of (NdDyTb)12.3 (FeZrNbCU)81.7-xCoxB6 ribbons optimally processed decreased from 1308.7 kA/m for x=0 to 817.4 kA/m for x=15. Optimum magnetic properties with Jr=1.041 T, Hci=944.9 kA/m and (BH)max=155.1 kJ/m3 were achieved by annealing melt-spun ribbon (x=-12) at 675℃ for 10 min. There was no significant influence of Co substitution on microstructure.     

Preparation of Rapidly Quenching （ Nd, Pr ） 12 （ FeCoZr ）82 B6 Alloy and Magnetic Properties of Bonded Magnets

TheanisotropyfieldHAofPr2 Fe14 Bisabout 30 %higherthanthatofNd2 Fe14 Bwhichresultsinhighin trinsiccoercivityfornanocrystallineexchangecoupledcompositepermanentmagnets .SothePr basedisotropicbondedmagnetshavecurrentlyattractedmuchattentions[1～ 4 ] .Howeverthistypeofpermanentmagnethasnotbeenusedinpractice .Thereexistmagneticinteractionsbetweenadja centgrainseitherinnanocrystallinecompositemagnetsorinanassemblyofsinglehardmagneticphaseofrareearth transitionmetalintermetalliccompounds[5～ 8] …     

注射成形粘结钕铁硼磁体复合粉研究

磁体的注射成形是一种高效生产的近净成形技术。为了制备出具有较好综合性能的注射成形粘结钕铁硼永磁材料,研究了粘结剂对注射成形磁体的磁性能、加工性能及力学性能的影响;分析了硅烷系列的偶联剂、复合润滑剂和抗氧剂等添加剂对注射成形磁体性能的影响。结果表明,用MQP-B快淬钕铁硼磁粉和尼龙12粘结剂制备出了剩余磁感应强度为0.539 T,磁感矫顽力为345.37 k A/m,内禀矫顽力为681.02 k A/m,最大磁能积为47.37 k J/m3的注射成形钕铁硼磁体。     

Investigation on the magnetomechanical behavior of trilayered GM actuator

In this article, it was suggested a TbFe/Co/Dy trilayered GM （Giant Magnetostrictive） film type actuator and investigated the magnetomechanical characteristics of the actuator for micro application. The trilayered films were fabricated at different thickness ratios to get an optimized structure. TbFe had positive GM properties, and cobalt, dysprosium layers made the magnetostriction property of composite film increase in low magnetic field. To fabricate the Si based microactuator with trilayered film, micromachining processes including RIE （Reactive Ion Etching） and selective DC magnetron sputtering techniques were combined. The deposited film thicknesses were measured by X-ray diffraction （XRD）. As a result, the magnetization of the film on the fabricated actuator was observed to characterize the magnetic properties of the TbFe/Co/Dy film using VSM （Vibrating Sample Magnetometer）. The magnetostriction of the actuator was determined by measuring the differences of curvature of the film coated silicon substrates using the optical cantilever method, and the deflections were also estimated under the external magnetic field lower than 0.5T for micro-system applications.     

Effect of chromium interlayer on magnetic exchange coupling of SmCo/Cr/TbFeCo multilayer thin films

A series of SmCo/Cr/TbFeCo multilayer thin films with perpendicular anisotropy were prepared by RF- magnetron sputtering system, and the effects of Cr interlayer thickness on magnetic properties and interlayer exchange coupling were investigated. It was found that the magnetic properties varied with the thickness of Cr interlayer, especially the values of saturation magnetization Ms and the coercivity Hc fluctuated periodically with the thickness of Cr interlayer. STM images revealed that the variation of coercivity Hc was attributed to the microstructure change of SmCo layer influenced by Cr interlayer, and the variation of Ms was related to interlayer exchange coupling.     

晶间合金化Ga元素对烧结Nd-Fe-B磁性能与显微组织的影响

用晶间合金化方式直接在(NdPr)29.6(FeCuZr)69.2B1.0粉中加入0.3%Ga(质量分数,以下同),磁体的内禀矫顽力从943.5kA/m提高到1181.0kA/m。分别用晶间合金化方式和传统合金化方式在(Nd-PrDy)30.0(FeCuZr)69.0B1.0中加入0.2%Ga,前者的内禀矫顽力达到1224.0kA/m,远高于后者的971.5kA/m。显微组织结构分析表明:用晶间合金化方式加Ga后改善了边界结构,没加Ga时晶粒边界不平直,晶界处缺陷较多;加Ga后晶界平直光滑,Ga主要分布在晶界,而晶内Ga含量极低。     

Effect of annealing process on magnetic properties of Sm（Co0.6Fe0.27Cu0.1Zr0.03）7.5 ribbons

Sm(Co0.6Fe0.27Cu0.1Zr0.03)7.5 ribbons were prepared by melt-spun method. The results showed that the remnant magnetization Mr and intrinsic coercivity Hci had a rapid increase when the heating rate increased from 5 to 10℃/min. But the increase of Mr and Hci were observed to be very little when the heating rate was further increased to 20℃/min. 10℃/min was the critical heating rate for obtaining high magnetic properties. The maximum values of Mr and Hci reached 0.70 T and 780.1 kA/m when the annealing temperature and annealing time were optimized to be 800℃ and 1 h, respectively. Proper second-step heat treatment could suppress the decrease of Hci when the cooling rate increased from 0.7 to 5 ℃/min, which could reduce the cooling time effectively.     

Effect of Ti cap layer thickness on microstructures and magnetic properties of Ti/Ni/Ti films

Nanogranular Ti (3 nm)/Ni(30 nm)/Ti(t nm) (t=1, 3, 5, 7, 10) films were prepared by facing magnetron sputtering from Ti and Ni onto glass substrates at room temperature. The structural and magnetic properties of films strongly depended on the Ti layer thickness. X-ray diffraction (XRD) patterns of all as-deposited films showed strong FCC Ni(111) peak. Vibrating sample magnetometer (VSM) measurements indicated that the perpendicular coercivity of the Ti (3 nm)/Ni (30 nm)/Ti (3 nm) film reached about 36 kA/m. With the increase of Co layer thickness, coercivity (H_c) first increased and then decreased. The grain size and magnetic clusters slightly increased and the value of roughness (R_a) was smallest at t=3 nm.     

稀土磁性功能薄膜材料的研究现状

稀土磁性功能薄膜材料由于具有优异的性能和巨大的需求潜力,将在很多领域中发挥重要的作用。本文对各种稀土磁性功能薄膜材料进行了较为系统的综述,重点评述了稀土永磁薄膜、稀土磁光薄膜、稀土磁泡薄膜和稀土磁致伸缩薄膜等稀土磁性功能薄膜材料的研究状况和最新进展。最后指出了稀土磁性功能薄膜材料存在的问题,并展望了它的应用前景。     

Multilayer Magnets

After experimental evidence of intergrain exchange coupling was reported, nanocomposite magnets with high remanence and large energy products were predicted. However, the experimental values of the maximum magnetic energy product of nanocomposite bulk magnets have been much less than the theoretically predicted ones. We gave a brief review on advances in multilayer magnets. The exchange coupling and remanence enhancement were realized in nanocomposite (Nd,Dy)(Fe,Co,Nb,B)_5,5/α-Fe thin films prepared by sputtering and heat treatments. Well-designed multilayer films consist of magnetically hard Nd₂Fe₁₄B-type phase with the grain size of 40 nm and magnetically soft α-Fe phase existing in the form of the continuous layers. Furthermore, we reported the structural and magnetic properties of anisotropic Nd-Fe-B thin films. The effects of thickness, deposition rates, substrate temperature, annealing temperature were studied. A high maximum energy product of (BH)_max = 270 kJ/m³ was obtained for anisotropic Nd-Fe-B thin films.     

Study on preparation technique and properties of magnetostrictive epoxy bonded Tb1-xPrx(Fe0.4Co0.6)1.93 composites

The magnetic and magnetostrictive properties of epoxy bonded Tb1-xPrx(Fe0.4Co0.6)1.93 (0.85≤x≤1.00) composites, prepared with different epoxy proportions using cold compression-molding technique, were investigated. It is found that the optimal conditions were with a compaction pressure of 100 MPa and a mass ratio of resin to powder of 5:100. The Tb0.1Pr0.9(Fe0.4Co0.6)1.93 composite rod had a high magnetostriction of 770 ppm at an applied magnetic field of 960 kA/m, whereas the Pr(Fe0.4Co0.6)1.93 composite reached 500 ppm at 400 kA/m. The good magnetostrictive properties of Pr(Fe0.4Co0.6)1.93 composite at low-field (≤400 kA/m) could be explained by its low anisotropy. These results indicated that the epoxy bonded Tb1-xPrx(Fe0.4Co0.6)1.93 rod samples for high Pr content of x=0.9-1.0 were of practical value.     

Enhancement of terbium efficiency by gallium and copper co-doping in (Pr,Nd)-Fe-B sintered magnets

It is well known that Tb substitution for (Pr, Nd) in (Pr, Nd)-Fe-B based sintered magnetic materials is an effective way to increase intrinsic coercivity, but it is not quite clear whether the increment depends on the different matrix phases with various doping ingredient or not, which is essential to develop high quality magnets with high coercivity more efficiently and effectively with economic consumption of expensive Tb and other costly heavy rare earths. In this paper, we investigated the efficiency of Tb substitution for magnetic property in (Pr, Nd)-Fe-B sintered permanent magnets by co-doping Ga and Cu elements. It is shown that Ga and Cu co-doping can effectively improve the efficiency of Tb substitution to increase the thermal stability and the coercivity. The intrinsic coercivity increases up to 549 and 987 kA/m respectively by 1.5 wt% and 3.0 wt% Tb substitution in Ga and Cu co-doped magnets while the intrinsic coercivity increases up to only 334 and 613 kA/m respectively by the same amounts of Tb substitution in non-Ga and low-Cu magnets. In other words, it demonstrates that there is about 329–366 kA/m linear equivalent enhancement of intrinsic coercivity by 1.0 wt% Tb substitution for (Pr, Nd) in Ga and Cu co-doped magnets. The temperature coefficients of both intrinsic coercivity β and remanence α at 20–150 °C by 3.0 wt% Tb substitution for the magnets with Ga and Cu co-doping are −0.47%/K and −0.109%/K respectively, and in contrast those values are −0.52%/K and −0.116%/K respectively for the non-Ga and low-Cu magnets. It is the principal reason for more efficient enhancement of magnetic property by Tb substitution in the Ga and Cu co-doped magnets in which Tb atoms are expelled from triple junction phases (TJPs) to penetrate into the grain boundary phases (GB phases) and thus modify the grain boundary. It is prospected that the efficiency of Tb substitution would rely on different matrix phases with various doping constituents.     

晶界扩散Dy–Al–Ga对钕铁硼磁体的磁性能和微观组织的影响

通过晶界扩散Dy₇₀Al₁₀Ga₂₀合金研究了烧结Nd-Fe-B磁体的磁性能和热稳定性能.用NIM-500C高温永磁测量仪和MLA650扫描电镜测出了磁体在扩散前后的磁性能和微观组织的变化.结果表明，在Dy₇₀Al₁₀Ga₂₀合金扩散热处理后，磁体矫顽力从原始的1 080.968 kA/m显著提升到1 671.600 kA/m，提升幅度约为55 %，而剩磁下降很少. Dy、Al、Ga元素在晶界处扩散，很好地隔绝了磁交换作用，提升矫顽力. SEM图显示在扩散Dy₇₀Al₁₀Ga₂₀合金后，可以很明显地看到晶粒外延层有一层灰色的壳层包覆着主相晶粒，很好地起到了隔离晶粒的磁交换作用. XRD显示主相的峰普遍往右偏移，这归因于重稀土元素Dy进入晶粒外延层形成（Nd, Dy）₂Fe₁₄B核壳结构. Dy的原子半径比Nd小，导致峰往右移.      

Effect of film thickness on magnetic properties of Cr/SmCo/Cr films

Cr/SmCo/Cr films with different SmCo thickness were deposited on glass substrates by magnetron sputtering,followed by an annealing process at 550 °C for 20 min.Experimental results showed that the SmCo film of 30 nm exhibited two-phase behavior in the demagnetization process,the obvious kink was observed near zero.For the SmCo film of 50 nm,the kink was invisible,and a single phase like behavior was obtained in the demagnetization process.The reversal behavior became consistent in the thicker films.Moreover,the coercivity reduced and the saturated magnetization increased obviously with the increasing thickness.X-ray diffraction results indicated that the average grain size of SmCo 5 in the thicker films were almost 30 nm,but the quantity of SmCo 5 grains increased with the increasing thickness,which enhanced the intergrain exchange coupling(IEC) of the SmCo 5 hard phases.The increase of IEC improved the magnetic properties of SmCo films with increasing thickness.