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Effects of Pt buffer layer and Sr content on the structure, surface morphology, ferroelectric, and magnetic properties of Bi1-xSrxFeO3 (BSFO) polycrystalline films on glass substrates at reduced temperature of 450 °C have been investigated. Perovskite single phase is present in the studied BSFO films ( x = 0.05 –0.15) on 10–30 nm thick Pt(111) electrodes. The grain size and surface roughness of BSFO films is closely related to the morphology of Pt(111) electrodes. Further refined microstructure with reduced surface roughness is found with the increase of Sr content x . BSFO polycrystalline thin films display good ferroelectric properties with the remanent polarization (2Pr) of 77–103 \mu \textC /cm2 and electrical coercive field ( Ec) of 380–490 kV/cm. In addition, the enhanced ferromagnetic properties with magnetization ( Ms ) of 8.7–11.2 emu/cm3 and coercivity ( Hc ) of 1211–1299 Oe are attained. [ABSTRACT FROM AUTHOR]

Structure and ferroelectric properties of multiferroic \BiFeO3 (BFO) films prepared by pulse laser deposition (PLD) with different substrates of \Pt/\Ti/\SiO2/{\Si}(100) and Pt/glass have been studied. Isotropic perovskite BFO phase is obtained in the 200-nm-thick BFO films deposited on both substrates at reduced substrate temperature Ts=400\-500^\circ{\C}. Uniformly finer grains and smoother surface are obtained for BFO films grown on Pt(111)/glass as compared to \Pt/\Ti/\SiO2/{\Si}(100) substrate. This difference may be related to the distinct BFO/Pt interface morphology. After postannealing, the Pt layer grown on glass substrates has very smooth surfaces consisting of (111) grains, while it contains cracks in the \Pt/\Ti/\SiO2/{\Si}(100). As a result, lower leakage current density and better ferroelectric properties of 2Pr=15.1\-78.6~\mu \C/cm^{2} and Ec=383\-514~\kV/cm are obtained in the BFO films deposited on Pt(111)/glass substrates. Nevertheless, high deposition temperature of 550 ^\circ\C leads to the formation of large amount of BFO into \Bi2{\O}3, \Bi2{\Fe}4{\O}9, and \Fe2{\O}3 phases, and therefore, no ferroelectric behavior is observed. [ABSTRACT FROM PUBLISHER]

The photovoltaic (PV) property of multiferroic \BiFeO_3 (BFO) nanocrystalline films with different textures on glass substrates has been studied. Highly textured BFO(001) films were obtained on ferromagnetic L1_0-FePt(001) bottom electrodes by sputtering, while the isotropic polycrystalline BFO films were prepared on 20-nm-thick Pt(111) bottom electrodes by pulse laser deposition. All studied BFO films exhibited significant PV effect under laser illumination with wavelength of 405 nm, and the short-circuit photocurrent density was increased with the increase of laser intensity. Large photocurrent density (Jsc) of 5.9~\mu\A/\cm^2 at laser power of 220~\mW/\cm^2 was obtained in the BFO(001) film grown on 20-nm-thick FePt electrode, and the value was larger than that of the isotropic single phase BFO film by a factor more than 1.7. This difference could be explained by the depolarization effect along different lattice orientations. Furthermore, it was found that the larger compressive residual strain in the BFO(001) film leads to a 34% decrement in Jsc, which was believed to result from the widened band gap. PV property was also sensitive to phase and roughness, the formation of \Bi2{\O}_3, and a roughened surface suppresses PV effect. [ABSTRACT FROM PUBLISHER]

Magnetic properties of directly quenched \R9.5{\Fe}72.5\-y{\Ti}2.5{\Zr}0.5{\Cr}_y{\B}15 \-x{\C}_x (\R=\Nd, Pr, and mischmetals (MM); x=0\-0.5; y=0\-1) bulk magnets with a diameter of 0.9-1.1 mm and a length of 15 mm have been studied. Thermal magnetic analyses show that large amount of 2:14:1 phase together with a slight \alpha\-\Fe phase are found for most of the developed magnets. Besides, a slight substitution of C for B and Cr for Fe in \Nd9.5{\Fe}72.5{\Ti}2.5{\Zr}0.5{\B}15 magnets can effectively refine the grain size of the bulk magnet, resulting in the remarkable enhancement of the magnetic properties. The optimal magnetic properties of \Br = 5.9~\kG, i\Hc=8.2~\kOe and (\BH)\max=7.2~\MGOe could be attained in \Nd9.5{\Fe}71.5{\Ti}2.5{\Zr}0.5{\Cr}_1{\B}14.5{\C}0.5. In addition, for \R9.5{\Fe}71.5{\Ti}2.5{\Zr}0.5{\Cr}_1{\B}14.5{\C}0.5 magnets, even though the magnets with \R=\MM exhibit slightly lower \Br and (\BH)\max than the magnet with \R=\Nd, magnetic properties of \Br=5.6\-5.7~\kG, i\Hc=10.3 \-11.4~\kOe, and (\BH)\max=6.0\-6.9~{\MGOe} can also be achieved for the magnets with \R = MM(A) and MM(B). [ABSTRACT FROM PUBLISHER]

Phase evolution, microstructure, and magnetic properties of Nd9.5 - 1.5xFebal.Ti2.5Zr0.5B15 + 2x (x=0\-4) rod magnets with a diameter of 0.9 mm have been investigated. For the as-cast magnets, large amount of 2:14:1 phase exists for x = 0, while an additional amorphous phase appears for x=1\--2, yet large amount of orthorhombic Fe3 B (o-Fe3B) phase is easily formed together with slight 2:14:1 and amorphous phases for x=3\--4. The appearance of amorphous phase with x=1\--2 results in the reduction of permanent magnetic properties drastically, which implies that annealing is necessary to improve the hard magnetic properties of these rod magnets. After annealing the magnets with x=1\--2, the amorphous phase is crystallized into 2:14:1 and Fe3 B phases, as a result, the magnetic properties were improved from Br = 4.7\--5.2 kG,i Hc =2.7\--10.9 kOe, and (BH)\max =1.1\--3.7 MGOe for the as-cast magnets to Br =5.7\--6.8 kG,i Hc =6.2\--7.4 kOe, and (BH)\max =5.5\--5.6 MGOe. For the magnets with x=3 and 4, annealing treatment is not necessary due to the existence of large amount of orthorhombic Fe3 B (o-Fe3B) in the as-cast state, consequently, exhibit extremely low permanent magnetic properties. [ABSTRACT FROM AUTHOR]

The magnetic properties and crystal structure of melt spun SmCo7-xSn_x (x=0–0.6) ribbons have been investigated. The XRD patterns of ribbons spun at a high wheel speed of 40 m/s show that a pure TbCu7-type structure is formed only for x=0.1, while a mixture of CoSn appears at the grain biundary for x\geqq 0.2 and 2:17 phase appears for x\geqq 0.4. The Rietvield refinement result shows that Sn prefers to occupy the 2e sites in TbCu7-type structure, which is similar to Ge. The coercivity of melt spun SmCo7-xSn_x ribbons is enhanced from 1.9 kOe for x=0 to 8.4 kOe for x=0.3. The grain size is reduced with Sn substitution from 100–400 nm for SmCo7 ribbons to 50–100 nm for SmCo6.7Sn0.3 ribbons, which also contributes the coercivity in addition to the enhancement of magnetic anisotropy field by the occupation of Sn atoms at 2e sites. [ABSTRACT FROM AUTHOR]

CoPt and CoPt/Au films prepared by magnetron sputtering were studied in this paper. The films were deposited at room temperature followed by a post annealing at temperatures (Ta) from 400°C to 800°C. Ordering of the CoPt and CoPt/Au films occurred at Ta = 600°C and 500° C, respectively, which results in magnetic hardening. With the increase of Ta up to 700° C, coercivity of the both films increased to a maximum value of about 12 kOe. As Ta reached 800°C, a drastic magnetic softening occurs in both samples; meanwhile, the diffraction data indicate a corresponding phase change from tetragonal to cubic. Scanning electron microscopy results revealed an intensive grain growth from 70 nm at 700°C to 160 nm at 800°C for CoPt/glass film and from 110 nm at 700°C to 250 nm at 800°C for CoPt/Au/glass sample. The relation between the abnormal phase change and intensive grain growth indicates that the formation of the cubic phase is driven by large biaxial tensile stress. Further investigations support this explanation and reveal that the cubic phase may be chemically ordered. [ABSTRACT FROM AUTHOR]

Fe53Pt47 and Fe58Pt42 thin films with 300 am in thickness prepared using magnetron sputtering were investigated. The films were deposited on heated glass substrates and annealed at 400°C and 800°C for different time. Single phase FePt films with similar chemical ordering but different substructure size were produced in the two series of samples. The effect of microstructure refinement results in significant enhancement in remanence (Mr) of about 38.1% and 30.8% in the Fe53Pt47 and Fe58Pt42 films, respectively. The energy product, (BH)max, also showed a large increase of 25% and 72%; the maximum value of the two series of films are 16.2 MGOe and 19.6 MGOe, respectively. The large (BH)max was found to originate from the enhancement of Mr and steep slope of demagnetization curve at coercive point (α). As the theoretical predictions, in an isotropic magnet, the magnetic moments in the transition region of magnetization near grain boundary are easy to be aligned by applied field. In this study, it is found that by increasing the magnetic transition region through microstructure refining, the remanence can be effectively enhanced meanwhile facilitate the collective magnetic reversal. Domain structure confirms that the refinement of microstructure effectively reduces the domain size. [ABSTRACT FROM AUTHOR]

The magnetic properties and phase evolution of Pr-lean and boron-enriched Pr8.5Feγ9.5M2B10 (M = Cr, Nb, V, Ti, and Zr) melt-spun ribbons have been studied. Based on thermal magnetic analysis (TMA), a slight substitution of the selected refractory elements (Cr, Nb, V, TI, and Zr) for Fe in Pr8.5Feγ9.5M2B10 not only suppresses the formation of metastable Pr2Fe23B3 and Fe3B phases but also leads to the presence of large amount of Pr2 Fe14B and α-Fe phases of fine grain size (<30 nm). Exchange coupling effect is found to exist in all nanocomposites, which is attributed to their finer grain size if suitable crystallization treatment is employed. As a result, the magnetic properties of the ribbons are Improved remarkably. The optlmum magnetic properties of Br = 9.6 kG, iHc = 8.5 kOe, and (BH)max = 17.8 MGOe are achieved in Pr8.5Feγ9.5Tl2B10, while the highest coercivity of iHc = 9.9 kOe (Br = 9.2 kG and (BH)max = 16.9 MGOe) is obtained in Pr8.5Feγ9.5Nb2B10. [ABSTRACT FROM AUTHOR]

Effect of Ag segregation on magnetic and structural properties of (FePt)77 Ag23 single-layer films were studied. Thin films were first sputtered on the heated glass substrates and cooled to room temperature, a post annealing at temperatures (Tp) from 200 C to 4000 C for 60 mm was then applied. Ll0 structure formed as substrate temperature (Tp) equals to 600 °C and 700 °C. For those ordered films, Ag was observed to precipitate as particles on the film surface and grow with the increasing Ts. After post annealing at 400 °C for 60 mm, those silver particles dissolved into the film, leading to changes in reversal behavior. The optimum condition is obtained in the = 600 °C, Ts = 400 °C sample. Drastic reduction in coercive squareness ratio (from >0.8 to 0.41) and enhanced coercivity (from 4.7 to 6.4 kOe) indicate the reversal behavior alters from cooperative to independent. Negative δM curve suggests that this independent rotation results from the reduction of exchange interactions. [ABSTRACT FROM AUTHOR]

FePt/SiO2 nanogranular thin films have been prepared by molecular-beam epitaxy system on MgO (001) substrates with the method of insertion dual SiO2 layers into Fe/Pt multilayer films. We report the relationships between the inserting thickness of SiO2 layers and the microstructural and magnetic properties of FePt thin films. It indicated the nanogranular FePt thin films were successfully formed by inserting amorphous SiO2 layers into the Fe/Pt films. The reduction of grain/domain size and isolation of FePt particles can be achieved by such insertion and maintain (001) texture. The average grain size of FePt films with 5-nm SiO2 insert layers is estimated to be around 8 nm, while domain rotation is enhanced depicting a decoupling of intergrain interaction. The isolated grains are less magnetically coupled in the rotation mode and the reversal of magnetization is more independent. [ABSTRACT FROM AUTHOR]

The magnetic properties, phase evolution, and microstructure of melt-spun Pr9Fe88.5-xTi2.5Bx(x = 7 to 15) nanocomposites have been investigated. From thermal magnetic analysis (TMA), the volume fraction of Pr2Fe14B phase increases and α-Fe phase decreases with increasing x, giving rise to the increment of iHc and the decrement of Br. But the average grain size of the ribbons is slightly decreased with the increment of boron content x, from 15-30 nm for x = 7 to 10-20 nm for x = 15. As a result, the optimum magnetic properties of Br = 9.5 kG, iHc = 10.8 kOe, and (BH)max = 17.8 MGOe can be achieved in Pr9Febal. Ti2.5B11. In addition, further substituting Co for Fe in Pr9Fe77.5-yCoyTi2.5B11 ribbons not only increases the Curie temperature of magnetic phases 2:14:1 and α-Fe, but also improves the thermal stability of the ribbons. Higher magnetic properties of Br = 9.7 kG, iHc= 11.3 kOe, and (BH)max = 18.5 MGOe are obtained in Pr9Fe67.5Co10Ti2.5B11 ribbons. [ABSTRACT FROM AUTHOR]

Single-layer polycrystalline Fe52Pt48 alloy thin films were deposited on preheated natural-oxidized (100) silicon wafer b y conventional sputtering method at room temperature. The as-deposited films are soft fcc FePt phase. After suitable temperature annealing and furnace cooling, the as-deposited films are transformed from disordered soft fcc FePt phase into ordered fct L10 FePt phase. The ordering temperature of L10 FePt phase could be reduced to about 350 °C by preheating substrate to 300 °C followed by furnace cooling treatment. The grain size of FePt was found to decrease as the ordering temperature of L10 FePt phase was reduced. After annealing at 350 °C for 1 h, the in-plane coercivity (Hc11) of the 100-nm Fe52Pt48 alloy thin film is about 6 kOe, and the average grain size is about 6 nm. [ABSTRACT FROM AUTHOR]