Effect of annealing in external magnetic field on the microstructure and magnetic properties of FePt films

We have studied the influence of annealing in an external magnetic field on the microstructure and magnetic properties of a multilayer Si/Fe(2 nm)/Fe₅₀Pt₅₀(20 nm)/Pt(2 nm) structure synthesized by means of sequential RF magnetron sputtering of the components. The magnetic field was oriented perpendicular to layers of the structure. It is established that annealing in the external magnetic field leads to the formation of predominant (001) texture in the multilayer structure with L1₀-FePt phase. Thus, a method of obtaining multilayer structures based on FePt films required for the perpendicular magnetic recording has been developed.     

Effect of field annealing angle on the magnetic properties of an amorphous Fe-B-Si-C alloy

Annealing amorphous ribbons in a field in the plane at an angle to the long axis induces an easy axis also at an angle to the long axis and decreases the domain width. These effects result in a decrease in the 60-Hz losses and for domain rotations of less than approximately 5°, there is no increase in exciting voltamperes or decrease in remanence. For domain rotations of greater than about 5° the losses continue to decrease, but the exciting voltamperes increase and the remanance decreases. These effects are consistent with the domain rotation induced by the annealing.     

(Nd1-xPrx)10.5(FeCoZr)83.5B6合金显微结构和磁性能研究

采用部分过快淬加后续晶化退火工艺,制备出了最佳磁性能的(Nd1-xPrx)10.5(FeCoZr)83.5 B6(x=O、0.2、0.4、0.6、0.8、1.0)系列粘结磁体,研究了稀土Pr元素对快淬合金DTA曲线转折温度点、合金显微组织结构和粘结磁体磁性能的影响.Pr元素使合金非晶态的晶化转变温度和转化能降低,合金的显微组织结构变得较粗大和较不均匀,从而使快淬粘结磁体剩磁降低.随Pr含量的增加,磁体的内禀矫顽力Hci单调上升,剩磁Br单调下降,在x=0.6～0.8处(BH)m达到最大值70.6kJ·m3.     

微量Ti对Mg-2Nd二元合金的组织和性能的影响

研究了微量Ti对Mg-2％Nd（N2）二元合金组织和性能的影响．结果表明，在不影响N2铸造性能的情况下，微量Ti的加入大大细化了N2铸态合金的组织，提高了铸态合金N2在室温和高温的强度和塑性．微量Ti的加入也使N2合金在中温条件下的抗蠕变性能略有提高．使用二维点阵错配度模型研究了Ti对Mg-Nd二元合金的细化机理，结果表明α-Ti可以成为α—Mg凝固过程中的形核核心．     

Mo元素对铁镍热磁合金性能的影响

为了进一步提高铁镍热磁合金的性能,系统研究了Mo元素对铁镍热磁材料的磁滞回线、Ms-T曲线和热磁性能的影响规律.结果表明:随Mo含量的增加,Fe65.84-xNi34.16Mox(x＝2,3,4,5)合金的磁滞回线逐渐变得扁平,饱和磁感应强度值(Bm)、饱和磁化强度值(Ms)和居里温度(Tc)单调下降,温度系数△B/△T(0～100℃)值呈先升高后降低的趋势,并在Mo含量为4at%附近出现最高值5.86mT/℃.     

退火温度对FeGaGeBCu(P)非晶纳米晶合金组织结构和软磁性能的影响

用单辊旋淬法制备了Fe76Ga5Ge5B13-xPxCu1(x=0,3,5,7)合金带材,并研究了退火温度对合金晶化行为、结构演变和磁性能的影响.结果表明,P元素替换B元素后,合金的非晶形成能力有所降低,但是提高了二次晶化相的热稳定性.同时,P添加一方面细化了纳米晶尺寸,降低了合金矫顽力,P含量为7％(原子分数)的合金...     

Effects of high magnetic field on thermodynamic properties of pure Fe and Cu

By the use of PPMS (Physics Property Measurement System), specific heat values of pure Cu at 2–300 K were determined under the magnetic field of 0, 3, 6 and 9 T, respectively. Magnetization curves of pure Fe under the magnetic field of 0–9 Twere obtained at different temperature ranging from 5 to 300 K. Analyses of the experimental results indicate that below 300 K, magnetic fields have no effects on the specific heat values of diamagnetic Cu and very little effects on those of ferromagnetic Fe.     

Effect of annealing on magnetic properties and microstructure of electroless nickel-copper-phosphorus alloy deposits

The relationship between magnetic properties and microstructure of the as-deposited and heat-treated Ni-Cu-P alloy deposits has been studied by means of vibrating sample magnetometry, differential scanning calorimetry. X-ray diffractometry and hot-stage transmission electron microscopy. The Ni-Cu-P deposits consist of low-P Ni-Cu solid solution crystallites and high-P-low-Ni-Cu amorphous phase. When the deposits are annealed at elevated temperatures, the Ni-Cu crystallites grow rejecting P from themselves and absorbing Cu from the neighbouring amorphous phase, while the P-rich amorphous phase transforms into Ni₅P₂ phase or into Ni₅P₂ and Ni₃P phases. The metastable Ni₅P₂ phase finally transforms into the stable Ni₃P phase. The non-magnetism observed in Ni-Cu-P deposits having a copper content above 28% in both as-deposited and annealed states, is attributed to their Cu-rich Ni-Cu solid solution crystallites. Nickel phosphides which crystallize from the amorphous phase existing mixed with the Ni-Cu crystallites in the as-deposited state, do not affect the saturated magnetic moment of the deposits.     

Effects of high magnetic field on thermodynamic properties of pure Fe and Cu

By the use of PPMS (Physics Property Measurement System), specific heat values of pure Cu at 2–300 K were determined under the magnetic field of 0, 3, 6 and 9 T, respectively. Magnetization curves of pure Fe under the magnetic field of 0–9 T were obtained at different temperature ranging from 5 to 300 K. Analyses of the experimental results indicate that below 300 K, magnetic fields have no effects on the specific heat values of diamagnetic Cu and very little effects on those of ferromagnetic Fe.     

Magnetic and structural properties of NdFeB thin film prepared by step annealing

The crystallization of the amorphous phase into the tetragonal Nd₂Fe₁₄B (Φ) phase and the corresponding changes in magnetic properties have been examined by step annealing experiment using a 2 μm thick NdFeB film sample. Microstructural and magnetic analysis indicate that the film was magnetically soft as deposited with the coercivity H_ci⊥ <16 kA m⁻¹ and the remnant magnetization 4πM_r⊥ <0.02 T. Annealing at a temperature of 550 °C, a coercivity value around 784 kA m⁻¹ was developed and diffraction analysis showed evidence of Φ phase 002l peaks being aligned perpendicular to the film plane. At an optimum annealing temperature of 575 °C, the remnant magnetization of this anisotropic thin film is around 0.60 T with intrinsic coercivity of ∼1340 kA m⁻¹. Annealing the film sample at 200 °C≤T_ann≤750 °C showed variations in magnetic properties that were mostly due to the change in the perpendicular anisotropy. Based on 4πM_s⊥ values plotted against T_ann, a dip in 4πM_s⊥ values was observed as T_ann increased in the soft-to-hard magnetic characteristics transition region and rose as the hard crystalline phase started to form. The results show that the magnetic properties of the NdFeB film were slightly influenced by the presence of NdO, film surface roughening and the small increase in crystal size as a consequence of repeated heat treatment. At T_ann ∼300 °C, the nominal saturation magnetization indicated a certain degree of weak perpendicular magnetic anisotropy in the film sample considered to be essential in the enhancement of coercivity in crystallized films.     

外磁场对Ni-Mn-Ga磁性形状记忆合金相变应变及显微组织的影响

研究了外磁场对Ni52Mn24.6Ga23.4(%,原子分数)单晶马氏体相变及其相变应变的影响,并对磁场增强相变应变的微观机制进行了探讨。研究结果表明无外加磁场时,NiMnGa合金发生马氏体相变时可产生约0.3%的收缩形变,沿单晶[100]方向施加外磁场,其相变应变随磁场的增加而呈近线性增加。当外磁场强度为6.37×105A/m时,应变量达到最大值(3.5%)。磁场作用下冷却形成的马氏体虽然孪晶亚结构不变,但自协作组态消失,并伴随有孪晶板条的增厚。磁场对马氏体相变应变的增强效应来自于磁场作用下的马氏体变体的择优取向。     

高温退火对高饱和磁感应强度Fe-Co合金磁性能的影响

对具有高饱和磁感应强度的1J22型Fe-Co软磁合金进行高温退火实验,并研究了其质量、磁性能随退火温度及时间的变化.结果表明,合金在500℃以下退火时,质量无明显增加且磁体磁性能并无降低;而当合金在500℃以上退火后,合金增重速率增加,且磁性能明显下降.当合金在600℃退火后,合金饱和磁感应强度Bs降至2178mT,矫顽力Hc增至76.1A/m.微观结构研究表明,高温退火后合金晶粒尺寸及形貌无明显变化,而合金表面完全生成Fe3O4.合金磁性能的降低是由氧化物的增多及杂质的引入造成的.     

Microstructure and properties of A357 aluminium alloy treated by pulsed magnetic field

This study examined the effects of a pulsed magnetic field (PMF) on the solidified microstructure and properties of A357 aluminium alloy. Results showed that the solidified microstructure of the alloy treated by a PMF was refined. The treated alloy in the T6 state had superior mechanical properties, with the ultimate tensile strength, yield strength and elongation increasing by 48?MPa (18.5%), 46?MPa (16.4%) and 4.8% (142%), respectively, when compared with the untreated alloy. When testing at room temperature, with a strain amplitude of 1?×?10^?4 and at a frequency of 1?Hz, the damping capacity value was 14.2?×?10^?3 for the alloy subjected to a PMF treatment, which increased by nearly 170% when compared with the untreated alloy.     

Fabrication of CoZn alloy nanowire arrays: Significant improvement in magnetic properties by annealing process

Highly ordered arrays of Co_1−xZn_x (0 ≤ x ≤ 0.74) nanowires (NWs) with diameters of ∼35 nm and high length-to-diameter ratios (up to 150) were fabricated by co-electrodeposition of Co and Zn into pores of anodized aluminum oxide (AAO) templates. The Co and Zn contents of the NWs were adjusted by varying the ratio of Zn and Co ion concentrations in the electrolyte. The effect of the Zn content, electrodeposition conditions (frequency and pH) and annealing on the structural and magnetic properties (e.g., coercivity (Hc) and squareness (Sq)) of NW arrays were investigated using X-ray diffraction (XRD), scanning electron microscopy, electron diffraction, and alternating gradient force magnetometer (AGFM). XRD patterns reveal that an increase in the concentration of Zn ions of the electrolyte forces the hcp crystal structure of Co NWs to change into an amorphous phase, resulting in a significant reduction in Hc. It was found that the magnetic properties of NWs can be significantly improved by appropriate annealing process. The highest values for Hc (2050 Oe) and Sq (0.98) were obtained for NWs electrodeposited using 0.95/0.05 Co:Zn concentrations at 200 Hz and annealed at 575 °C. While the pH of electrolyte is found to have no significant effect on the structural and magnetic properties of the NW arrays, the electrodeposition frequency has considerable effects on the magnetic properties of the NW arrays. The changes in magnetic property of NWs are rooted in a competition between shape anisotropy and magnetocrystalline anisotropy in NWs.     

退火温度对SmCo永磁薄膜微结构及磁性能的影响

采用直流磁控溅射法制备SmCo薄膜,研究了退火温度对薄膜微结构及磁性能的影响。XRD分析结果表明,当退火温度为600℃时,SmCo5相析出,而Sm2Co17相在700℃析出。SEM照片可看出,退火温度高于900℃时,六方柱状的SmCo5相和菱方状的Sm2Co17相全部析出。随着退火温度的升高,晶粒尺寸增大,当温度达940℃时,晶粒尺寸减小,而在980℃时,晶粒尺寸又将增大。VSM测试表明,与制备态的薄膜相比,退火后的薄膜在垂直于膜面方向的矫顽力、剩余磁化强度及最大磁能积都增大。960℃时得到矫顽力和剩余磁化强度的最大值,800℃时得到最大磁能积的最大值。     

注射工艺对高磁粉装载量PPS/NdFeB粘结磁体磁性能的影响

高磁粉装载量PPS/NdFeB注射磁体的制备是目前国内外研究的重点.成功制备出磁粉装载量90％(质量分数)左右的PPS/NdFeB粘结磁体以及可实际应用永磁元器件,应用DSC、SEM和磁化曲线测量仪等表征了注射磁体微观结构和磁性能,并分析注射温度、速度和压力等工艺参数对粘结磁体微观结构和磁性能的影响规律和机理,结果表明...     

添加润滑剂对烧结钕铁硼磁体性能的影响

研究了烧结钕铁硼永磁材料的粉末流动性及添加润滑剂对粉末流动性与磁体取向度和磁性能的影响.结果表明:影响松装状态磁粉流动性的主要因素是粉末颗粒团聚,影响密实磁粉流动性的主要因素是颗粒间的摩擦力.添加适量的润滑剂可以防止粉末颗粒团聚、明显地减小摩擦力,改善粉末流动性,提高磁体的取向度、剩磁与磁能积.采用添加润滑剂和橡皮模等静压制成型工艺,批量生产的烧结钕铁硼磁体性能达到:Br=1.457 T,jHc=1148 kA/m(14.43 kOe),(BH)max=408 kJ/m3(51.3 MGOe).     

Nd对AM50力学性能及高温性能的影响

对加Nd的AM50镁合金铸态试样进行固溶处理(420℃/12 h),研究了Nd对其显微组织、力学性能和抗高温蠕变性能的影响.结果表明:Nd的加入细化了晶粒,导致AM50合金室温力学性能的提高.Nd在AM50合金中形成了Al11Nd3高温稳定相,Al11Nd3的存在使加Nd的AM50合金在200℃的稳态蠕变率及高温(150℃)力学性能大幅度提高.     

Effects of high-temperature annealing on magnetic properties of (Zn0.91Mn0.09)O thin films grown by RF magnetron sputtering

The (Zn_0.91Mn_0.09)O thin film annealed at 1000 °C for 60 min in N₂ atmosphere showed two kinds of Curie temperature (T_C) values of T_C1 around 130 K and T_C2 above 300 K while the as-grown (Zn_0.91Mn_0.09)O thin film showed typical ferromagnetism with the T_C of 108 K. It is expected that the increase of T_C up to T_C1 might be attributed to the enhancement of crystal magnetic anisotropy because the increases of (0 0 0 l) peak for X-ray diffraction patterns and Mn²⁺-related emission for photoluminescence spectra were observed for annealed (Zn_0.91Mn_0.09)O thin films. The increase of T_C above T_C2 might be originated from the formation of nano-sized (Zn_0.91Mn_0.09)O islands because it was confirmed that the nano-sized (Zn_0.91Mn_0.09)O islands were formed after annealing treatment and that they revealed clearly the magnetic domains at 300 K for the measurements of atomic force microscopy and magnetic force microscopy, respectively. The room temperature ferromagnetism in the nano-sized (Zn_0.91Mn_0.09)O islands is considered to be originated from the inhomogeneous distribution of Mn ions.