Calculated X-ray magnetic circular dichroism of the ordered and disordered FePd alloy

A theoretical investigation of the effect of disorder and substrate on the magnetic properties of the FePd alloy is presented. The magnetic moments at the Fe sites decrease as the c/a ratio decreases, while the induced Pd magnetic moments increase. The disorder effect seems to be more important for the X-ray magnetic circular dichroism (XMCD) of Fe and Pd edges than the strain effect induced by the substrate.     

Si3N4/FePd/Si3N4薄膜的晶体结构和磁性能研究

采用磁控溅射的方法制备了Si₃N₄/FePd/Si₃N₄三层膜, 研究了非磁性材料Si₃N₄作为插入层对磁记录FePd薄膜结构与磁性能的影响。结果表明, 热处理后Si₃N₄分布在FePd纳米颗粒之间, 抑制了FePd晶粒的生长, 与纯FePd薄膜相比, Si₃N₄/FePd/Si₃N₄薄膜的颗粒明显得到细化; 通过添加Si₃N₄层, FePd薄膜的晶体学参数c/a从0.960减小到0.946, 表明Si₃N₄可以有效促进FePd薄膜的有序化进程, 同时提升了矫顽力和剩磁比, 分别提高到249 kA/m、0.86; 随着600℃退火时间的进一步延长, 添加Si₃N₄的薄膜磁性没有迅速下降, 在较宽的热处理时间范围内磁性能保持在比较高的水平, 提高了抗热影响的能力。Si₃N₄作为插入层对FePd薄膜的磁性能具有较大的提升作用, 这对磁记录薄膜的发展具有重要意义。     

改变薄膜厚度对玻璃衬底上FePd薄膜的结构和磁性能的影响

采用磁控溅射方法在玻璃衬底上制备了不同厚度的FePd合金薄膜。研究了薄膜厚度对结构和磁性能的影响。实验表明,在FePd合金薄膜中有序化过程发生在更厚的薄膜中。随着薄膜厚度从d=22.5nm增加到67.5nm,面内矫顽力刚开始急剧增大,然后随着薄膜厚度的进一步增加矫顽力会减小。在d=67.5nm时面内矫顽力最大约为3200Oe。     

FePd合金超微粒子的制备与性能

研究了用惰性气体凝聚法制备FePd合金超微粒子(UFP),并测定其产物性能结果表明,母合金的成分及组元的活度系数对产物有重要的影响,只有蒸发N_(Fe)=0.5的合金,才能制得均匀的单相合金超微粒子,用XRD,TEM和DSC分析表明Fe_(50)Pd_(50)合金的UFP稳定性比Fe的UFP提高,其矫顽力较相同成分的粗粉提高几倍并可达4.30×10~4A/m以上     

溶剂热法制备FePd纳米颗粒及其性能研究

以对环境友好的Fe(acac)3和Pd(acac)2作为主反应物,PEG-400为还原剂,通过简易的溶剂热法制备了FePd纳米颗粒,并对其磁性能和电催化活性进行了研究。结果表明：合成态的样品中FePd纳米颗粒为fcc相,其磁性能表现为超顺磁性,并对乙醇氧化表现出了一定的电催化活性。经过95%Ar+5%H2气氛下热处理后,FePd纳米颗粒从fcc相转变为fct相,磁性能转变为硬磁性,内禀矫顽力达到1.8 kOe,而且样品对乙醇氧化的电催化活性较之热处理前明显提高,峰值电流密度达26.6 mA/mg。     

Electrochemical synthesis of compositionally modulated FexPd1−x nanowires

Fe_xPd_1−x nanowires were electrodeposited by template-directed growth from ammonium citrate baths by adjusting the current density and metal ions concentration ratio (Fe²⁺:Pd²⁺). A higher current density and ion ratio led to the synthesis of the amorphous Fe-rich FePd nanowires, whereas nanocrystalline Pd-rich FePd nanowires could be obtained by the low ion ratio and current density. To minimize the longitudinal compositional modulation in high aspect ratio pores, pulse current were applied instead of direct current. Also, based on the ability to vary the composition of FePd by adjusting average current density, compositionally modulated FePd nanowires were synthesized at fixed duty cycle.     

Structural and magnetic properties of FePd and CoPd alloy epitaxial thin films grown on MgO single-crystal substrates with different orientations

FePd and CoPd alloy thin films were prepared on MgO single-crystal substrates of (001)_B1, (110)_B1, and (111)_B1 orientations at 600 °C by ultra high vacuum rf magnetron sputtering. L1₀-FePd(001) films with the c-axis perpendicular to the substrate surface are obtained on MgO(001)_B1 substrates. FePd epitaxial films consisting of L1₀(110) and L1₀(011) crystals are formed on MgO(110)_B1 substrates. The c-axis of L1₀(110) crystal is parallel to the substrate surface, whereas that of L1₀(011) crystal is 44° canted from perpendicular direction. L1₀-FePd(111) films with the c-axis 54° canted from the perpendicular direction are formed on MgO(111)_B1 substrates. L1₀ ordering degree of these FePd films varies depending on the substrate orientation. On the other hand, disordered CoPd thin films of (001)_A1, (110)_A1, and (111)_A1 orientations epitaxially grow on MgO substrates of (001)_B1, (110)_B1, and (111)_B1 orientations, respectively. The magnetization properties of L1₀ ordered FePd and A1 disordered CoPd thin films are influenced by the crystal structure, the ordering degree, and the film orientation.     

Magnetocaloric effect in melt-spun FePd ribbon alloy with second order phase transition

Magnetic entropy change and refrigerant capacity for an applied magnetic field variation of 1.5 T have been determined in the temperature range of 293-700 K for the as-quenched polycrystalline Fe_73.2Pd_26.8 melt-spun ribbons alloy. Samples show a major magnetic phase with the fct crystal structure and a Curie temperature of 553 K, at which a second order magnetic phase transition occurs. A maximum magnetic entropy change of 1.04 J kg⁻¹ K⁻¹ was achieved at 550 K, while the maximum refrigerant capacity of 108 J/kg is attained at the applied field of 1.5 T. The field dependence of the magnetic entropy change for this material follows the phenomenological universal curve and at the temperature of the peak corresponds to a large field independent exponent of n = 0.84. Extrapolated value of field depending RC_Area at 5 T reach above 300 J/kg, which is comparable to that of some of the best-known Fe-doped GdSiGe coolant compounds.     

沉积厚度对L10-FePd颗粒膜结构和磁性能的影响

采用直流磁控溅射法在石英玻璃基片上制备不同厚度的FePd纳米颗粒膜,利用X射线衍射仪、X射线能谱仪、扫描电子显微镜、原子力显微镜和振动样品磁强计表征薄膜的结构和磁性能。结果表明,经过550℃热处理3h后,薄膜的X射线衍射谱中出现(002)超晶格衍射峰,表明薄膜中出现了四方有序结构。随着薄膜厚度的减小其有序化程度增加,在膜厚为47nm时,样品矫顽力达到3.5kOe,剩磁比达到0.94,最大磁能积((BH)_(max))达到17.6 MGOe。FePd薄膜的相转变温度降低,磁性能较好。     

Electrodeposition of iron–palladium thin films

FePd thin films were electrodeposited from ammonium citrate complex baths. The effects of various electrodeposition and post heat treatment conditions including pH, current density, bath concentrations, substrates and annealing temperature on composition, material, and magnetic properties were systematically investigated. In these baths, the deposited iron content increased linearly with an increase in current density from 1 to 5 mA cm⁻² producing films with compositions extending from Fe₇Pd₉₃ to Fe₉₁Pd₉. Magnetic saturation (M_S) of electrodeposited FePd thin films linearly increased with increase in deposited iron content (i.e. 1.8 T for Fe₈₂Pd₁₈ and 0.1 T for Fe₁₉Pd₈₁) which is similar to its bulk counterparts. The effects of post-heat treatment on the phase and crystal structure of near equiatomic FePd electrodeposits (i.e. Fe₄₈Pd₅₂) was investigated by subjecting electrodeposits to different annealing temperatures from 400 to 600 °C under reducing environment. L1₀ FePd phase was formed from nanocrystalline FePd solid solution and the crystallinity improved with increasing annealing temperatures.