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Abstract: Perovskite bismuth ferrite (BiFeO3) layer, which is widely recognized as a multiferroic material, was prepared on a c-axis-oriented strontium ferrite (SrFe12O19) layer by magnetron sputtering to form a BiFeO3/SrFe12O19 bilayer. Direct observations of the magnetic and electric domains originating from the magnetism coincident with the ferroelectricity of BiFeO3 in the bilayer were achieved through magnetic force microscopy and electrostatic force microscopy, respectively. Simultaneous existence of magnetic and electric domains was observed in the BiFeO3 phase. A pinning effect of BiFeO3 in relation to SrFe12O19 was suggested from the magnetic hysteresis curves, although BiFeO3 layer exhibits a small magnetization. By applying a magnetic field to the BiFeO3/SrFe12O19 bilayer, the electric domains in the BiFeO3 layer sensitively respond, which implies that ferroelectric polarization in BiFeO3 layer can be magnetically controlled. [Copyright &y& Elsevier]

Abstract: Sm–Co and Nd–Fe-B thin films have been prepared by sputtering. Particular efforts are concentrated on the perpendicular texture growth of the films. The Sm–Co and Nd–Fe–B thin films with perpendicular magnetic anisotropy can be prepared on Cu and W underlayer, respectively. Those underlayers play an important role to prevent oxidation and improve crystal lattice orientation. Perpendicular coercivity and remanent squareness ratio are higher than 10kOe and almost 1.0, respectively, in both films prepared under optimum conditions. [Copyright &y& Elsevier]

Abstract: Pt, Pd, and Pt–Pd alloy underlayers were used to deposit c-axis oriented barium ferrite (BaM) thin films by a facing target sputtering system. All of the BaM thin films grown on these three underlayers show c-axis orientation normal to the film plane. But the grain size of BaM layer is strongly manipulated by the underlayer grain size. It is found that Pt–Pd alloy underlayer is effective to achieve c-axis oriented barium ferrite films with small grain size. [Copyright &y& Elsevier]

Abstract: A novel process to prepare hexagonal ferrite films with dot arrays has been proposed. Two immiscible elements, Al and Si, were first deposited onto a Si (111) substrate at various temperatures. The microstructure of this kind of film depends on the concentration and deposition temperature. Scanning electron microscopy (SEM) results show that structures with Al dot arrays, in the size range of 30–50nm, embedded into an amorphous Si matrix can be obtained by precise control of the sputtering conditions. Amorphous Ba–Fe–O films were deposited onto the dot array films at room temperature and then annealed to crystallize in part. Experimental results indicate that amorphous Ba–Fe–O films on Al dots can be crystallized by flash annealing the samples at 700°C for 60s. However, those on the amorphous Si keep the amorphous state. A structure with magnetic dot arrays embedded into a nonmagnetic matrix has been achieved by this process. The magnetic properties of the samples have been discussed. [Copyright &y& Elsevier]

Abstract: BaFe12− x (Mn0.5Cu0.5Zr) x /2O19 hexaferrites with x=1, 2 and 3 were prepared by sol–gel process. The ferrite powders possess hexagonal shape and are well separated from one another. The powders of these ferrites were mixed with polyvinylchloride (PVC) plasticizer to be converted into a microwave absorbing composite ferrite with a thickness of 1.8mm. X-ray diffractometer (XRD), scanning electron microscope (SEM), ac susceptometer, vibrating sample magnetometer and vector network analyzer were used to analyze its structure, electromagnetic and microwave absorption properties. The results showed that magnetoplumbite structures for all samples were formed. The sample with higher magnetic susceptibility and coercivity exhibits a larger microwave absorbing ability. Also the present investigation demonstrates that a microwave absorber using BaFe12− x (Mn0.5Cu0.5Zr) x /2O19 (x=2 and 3)/PVC with a matching thickness of 1.8mm can be fabricated for applications over 15GHz, with reflection loss more than −25dB for specific frequencies, by controlling the molar ratio of the substituted ions. [Copyright &y& Elsevier]

Abstract: FePt films were prepared by RF sputtering using Ne, Ar, and Kr as sputtering gas. The effects of sputtering gas on the microstructure and magnetic properties were studied. Both magnetic and crystallographic properties show that Kr gas promotes the formation of L10 phase. The films prepared by using Ar and Ne gas have random orientation, whereas the films prepared by using Kr gas show preferential c-axis perpendicular to the film plane orientation. [Copyright &y& Elsevier]

Abstract: Patterned magnetic media have been considered as one of the promising candidates for future ultra-high-density magnetic recording. In this paper, a new kind of patterned medium based on hexagonal ferrite have been studied. We have successfully fabricated strontium ferrite dot arrays by electron beam lithography. Their magnetic properties are evaluated by magnetic force microscopy (MFM) and superconducting quantum interference device (SQUID). The results show the dot arrays have perpendicular anisotropy. Dots with the lateral size larger than 500nm show multidomain magnetization configuration in the initial magnetization state. However, with dot size decreased to 500nm, all the dots have single-domain configuration both in the initial magnetization state and remanent magnetization state. [Copyright &y& Elsevier]

Abstract: A new technique, which utilizes the interlayer diffusion, for preparation of self-assembled nanodot magnetic structures has been proposed. L10-phase Pt/FeCu and Pt/FeAg films have been successfully synthesized by this technique. Both the coercivity of Pt/FeCu and Pt/FeAg films exhibited, respectively 4.1 and 8.0kOe in perpendicular direction. Pt/Fe and Pt/FeAg films show positive values, while Pt/FeCu shows negative value in δm plot. The results indicate that the exchange coupling between the grains has been decoupled in the self-assembled nanodot structure in Pt/FeCu film. [Copyright &y& Elsevier]

Abstract: TiN thin film is prepared by DC reactive sputtering in Ar+N2 atmosphere and its suitability as underlayer and overlayer for TbFeCo perpendicular recording media as well as its effect on the magnetic properties of the latter have been studied. Only 5nm TiN overlayer and 20nm under layer can successfully protect the TbFeCo film from oxidation. Initially the coercivity is increased sharply from about 2 to 6kOe for an increase of underlayer thickness to 60nm then the increasing rate of coercivity becomes very slow. The saturation magnetization remains almost constant with the underlayer thickness. The remanent squareness ratio remains constant at 1.0 with the underlayer thickness up to 60nm then decreases. [Copyright &y& Elsevier]

Abstract: Strontium ferrite (SrM) thin films were deposited on thermally oxidized silicon wafer with Au underlayer. Gold underlayers were prepared at various substrate temperatures by using a magnetron sputtering system. C-axis oriented SrM perpendicular films and preferred (111) orientation of underlayer have confirmed by X-ray diffraction patterns. The intensity of (111) diffraction line for Au and that of (00 l) diffraction line for strontium ferrite decrease with increase in substrate temperature (T u) The maximum coercivity and remanent squareness ratio in perpendicular direction, at T u of 500°C, are 5.4kOe and 0.68, respectively. The strength of the intergranular interaction of SrM magnetic particles is described by the parameter Δm. The SrM/Au films prepared at T u above 100°C have smaller Δm peak values than that for SrM/Au films prepared at T u of room temperature. This behavior is related to low magnetostatic coupling between the magnetic particles separated by the non-magnetic amorphous phase. [Copyright &y& Elsevier]

Abstract: Strontium ferrite (SrM) thin films deposited on thermally oxidized silicon wafer (SiO2/Si) and single crystal sapphire with (00 l) orientation (Al2O3(00 l)) substrate using Pt underlayer were prepared by DC magnetron sputtering system. It was found that the intensity of (111) line for Pt and that of (00 l) diffraction line for SrM increases with increasing substrate temperature, Tu . The c-axis dispersion angle, Δθ 50, of SrM(008) depends on that of Pt underlayer. Both dispersion angle of Pt(111) and SrM(008) decrease with increasing temperature. It was observed that the saturation magnetization of SrM/Pt deposited on SiO2/Si is higher than that of Al2O3 substrate. The coercivity and remanent squareness ratio in perpendicular direction are higher than that in in-plane direction. The maximum of coercivity in perpendicular direction of SrM/Pt films deposited on single crystal Al2O3 is about 4.2kOe. [Copyright &y& Elsevier]

Abstract: Strontium ferrite SrFe12O19 (SrM) thick films have been synthesized using a spinning coating sol–gel process. The coating sol was formed from SrFe12O19 powders dispersed in the strontium ferrite raw sol. XRD, TEM, SEM, vibrating sample magnetometer (VSM) and ac susceptometer were employed to evaluate the structure, composition and magnetic properties of SrFe12O19 thick films. The results indicated that a uniform and crack-free coating of Strontium ferrite with ∼15μm thickness can be produced with a good deal of consistency. The magnetization hysteresis loops were almost the same for magnetic fields both applied in parallel and perpendicular. [Copyright &y& Elsevier]

Highlights • Spintronic devices based on domain wall (DW) devices have attracted great interest. • Domain wall racetrack memory has the potential for high-density storage. • Precise control of domain wall motion is a challenge. • We have studied the use of nanoscale compositional variation to pin the domain walls. • To achieve nanoscale compositional mixing, Cr crossbars were used. • Moreoever, we have carried out a novel minor loop investigation of magnetoresistance. • Minor loop study has provided a better understanding of the underlying physics. Abstract Magnetic domain wall memory technology, wherein the information is stored in magnetic domains of multiple magnetic nanowires, is a potential concept proposed to store the large amount of digital data in the near future, which is generated due to the widespread use of social media and computing devices. However, one of the technological challenges which remains to be solved in domain wall memory is the controllable pinning of the domain walls at the nanometer scale. Here, we demonstrate the possibility to stabilize domain walls with nanoscale modification of magnetic properties by using thermal diffusion of elements from crossbar configuration. We have inspected and evaluated the magnetic properties of the nanowires using Kerr microscopy. The pinning field induced by Cr diffusion of our Ni 80 Fe 20 nanowire was estimated to be about 8 kA/m as determined from minor loop (magnetoresistance vs. magnetic field) measurements. The proposed concept can potentially be used in future domain wall memory applications. [ABSTRACT FROM AUTHOR]

Highlights • Prepared Nd-Fe-B films with perpendicular magnetic anisotropy at lower temperature. • Improved magnetic anisotropy and c-axis orientation by Tb additions. • Demonstrated correlations between as-deposited amorphous crystallized films. • Revealed the origination of crystallographic properties of annealed Nd-Fe-B films. Abstract Nd-Fe-B films with perpendicular magnetic anisotropy are important for various applications. Most common process to prepare Nd-Fe-B thin films with perpendicular magnetic anisotropy is the heteroepitaxy process. Here, Nd-Fe-B thin films with perpendicular magnetic anisotropy were prepared by a two-step process. Amorphous and magnetically soft thin films were first deposited. Crystallized, magnetic hard thin films were obtained by rapid thermal annealing of the as-deposited films. A clear correlation between perpendicular magnetic anisotropy of annealed state and the domain configuration in the as-deposited state was noticed. Films prepared without substrate heating, with additions of Tb show perpendicular coercivity which is larger than 24 kOe. [ABSTRACT FROM AUTHOR]

Due to the good stability and high mobility, magnetic skyrmions are considered for information carriers in future racetrack memory and spintronic devices. Here, we study the effect of the barrier at the edges on the dynamics of skyrmions in the Co/Pt bilayer racetrack, where the barrier is induced by a higher perpendicular magnetic anisotropy due to the hard magnetic material attached to the racetrack edges. In particular, we study the dynamics of skyrmions in the racetrack with a rectangular notch on one side of the boundary barrier. We systematically investigate the effect of the boundary barrier on the longitudinal velocity of the skyrmion. Compared with the model with no boundary force, it is found that when the repulsive effect of the boundary barrier just overcomes the Magnus force, the longitudinal velocity of the skyrmion can be increased significantly. We also find that a rectangular notch at the edge can be used to enrich the dynamics of the skyrmion. Based on the dynamic behaviors of skyrmions, we realize the skyrmion-based logic AND, OR, NOT, NAND and NOR gates and the diode in the same racetrack. In particular, the logic NOT, NAND and NOR gates are implemented in a reconfigurable way. Our results may be helpful for understanding the dynamics of skyrmions and may contribute to the design of non-volatile spintronic devices with integrated multiple functions and ultra-low energy consumption. [ABSTRACT FROM AUTHOR]

Abstract: In this study Cu x Mg0.5−x Zn0.5Fe2O4 (x=0–0.5) nanoparticles and thin films were prepared by sol–gel processing. The morphologies of nanoparticles were observed by transmission electron microscope (TEM). The Mössbauer spectroscopy (MS) was employed to determine the site preference of the constitutive elements. Magnetic dynamics of the nanoparticles was studied by the measurement of AC magnetic susceptibility versus temperature at different frequencies. The phenomenological Néel–Brown and Vogel–Fulcher models were employed to distinguish between interacting or non-interacting system. Results exhibited that there is strong interaction between fine particles. X-ray diffraction (XRD) patterns of the thin films indicate the formation of single-phase cubic spinel structure. Atomic force microscope (AFM) was employed to evaluate the surface morphologies of the prepared thin films. Vibrating sample magnetometer (VSM) was employed to probe magnetic properties of samples. It was found that with an increase in the amount of copper, the saturation of magnetization and initial permeability increase. [Copyright &y& Elsevier]

• Antiskyrmion manipulated by voltage-controlled magnetic anisotropy gradient. • The skyrmion hall effect suppressed using the bilayer antiskyrmions. • The bilayer antiskyrmions move faster than the skyrmion-antiskyrmion pair. • The relations of antiskyrmion velocities and the coupling strength are explored. Magnetic skyrmions could serve as information carriers in next-generation information storage and processing devices. Effective manipulation of the skyrmion motion is a vital task for realizing skyrmion-based applications. Skyrmion motion driven by voltage-controlled magnetic anisotropy (VCMA) has been proposed, of which the investigation is mostly focused on the dynamics of skyrmions. Here, using micromagnetic simulations we show that antiskyrmions can be effectively driven by the VCMA gradient in the presence of the anisotropic Dzyaloshinskii-Moriya interaction. We find that the antiskyrmion shows a transverse motion, i.e., the skyrmion Hall effect, induced by the VCMA gradient. As the skyrmion number of an antiskyrmion is opposite to that of a skyrmion, the anisotropy gradient-induced motion of ferromagnetically coupled skyrmion-antiskyrmion pair and antiferromagnetically coupled skyrmion-skyrmion and antiskyrmion-antiskyrmion pairs do not show the skyrmion Hall effect. We find that the velocity-driving force relations of these three combinations are different. Our results may provide guidelines for building future skyrmion-based information processing applications. [ABSTRACT FROM AUTHOR]