Search

We demonstrate that perpendicular anisotropy can be induced in Co2FeAl0.5Si0.5 by depositing the Heusler alloy on a tungsten seed layer. This is increased by elevating the deposition temperature to a moderate value up to 335 K. These perpendicular layers can be implemented into GMR devices, showing layer-thickness dependent switching without the use of an antiferromagnetic pinning-layer. These layers can be implemented into the manufacturing process of read-heads, where temperatures are limited.

We have used polar Kerr microscopy to study the magnetic domain structure in an ultrathin Au/Co(1 nm)/Au layer with perpendicular magnetic anisotropy. We present our demagnetization method of the sample. In the demagnetized state, we observed a dendritic domain structure. We theoretically calculated the lateral domain size in the demagnetized state by using two different models and we saw that the prefactor x = 0.389 corresponds to the domain structure observed. We used polar magneto-optical Kerr effect magnetometry (PMOKE) to study the magnetization reversal and to extract an activation energy E a in zero field and the width of the distribution of the energy barriers σ w . We correlated the dendritic domain structure observed with the large value of σ w .

CoFeB/MgO-based perpendicular magnetic tunnel junctions (p-MTJ’s) with high anisotropy and low damping are critical for spin-torque transfer random access memory (STT-RAM). Most schemes of making the pinned CoFeB fully perpendicular require ferrimagnets with high damping constants, a high temperature-grown L10 alloy, or an overly complex multilayered synthetic antiferromagnet (SyAF). We report a compositional study of perpendicular CoxPd alloy-pinned Co20Fe60B20/MgO based MTJ stacks, grown at moderate temperatures in a planetary deposition system. The perpendicular anisotropy of the CoxPd alloy films can be tuned based on the layer thickness and composition. The films were characterized by alternating gradient magnetometry (AGM), energy-dispersive X-rays (EDX), and X-ray diffraction (XRD). Current-in-plane tunneling (CIPT) measurements have also been performed on the compositionally varied CoxPd MTJ stacks. The CoxPd alloy becomes fully perpendicular at approximately x = 30% (atomic fraction) Co. Full-film MTJ stacks of Si/SiO2/MgO (13)/CoXPd100−x (50)/Ta (0.3)/CoFeB (1)/MgO (1.6)/CoFeB (1)/Ta (5)/Ru (10), with the numbers enclosed in parentheses being the layer thicknesses in nm, were sputtered onto thermally oxidized silicon substrates and in-situ lamp annealed at 400 °C for 5 min. CIPT measurements indicate that the highest TMR is observed for the CoPd composition with the highest perpendicular magnetic anisotropy.

Here we propose a method of the excitation of perpendicular standing spin waves (PSSWs) of different orders in an optomagnonic microcavity by ultrashort laser pulses. The microcavity is formed by a magnetic dielectric film surrounded by dielectric non-magnetic Bragg mirrors. Optical cavity modes in the magnetic layer provide concentration and strongly non-uniform distribution of the optical power over the layer thickness and therefore induce the effective field of the inverse Faraday effect also spatially non-uniform. It results in excitation of PSSWs. PSSWs whose wavevector is closest to the wavevector characterizing distribution of the inverse Faraday effect field are excited most efficiently. Consequently, a key advantage of this approach is a selectivity of the PSSW excitation which allows to launch PSSWs of required orders only. All-optical operation of the optomagnonic cavities opens new possibilities for their applications for quantum technologies.

We present a study of perpendicular magnetic anisotropy in [Co/Ni(t)/Co/Pt]×8 multilayers for use as free layers in magnetic tunnel junctions (MTJ) and spin valves. The thickness t of the Ni sub-layer was varied and the resulting magnetic properties were investigated. As determined from magnetic force microscopy and magnetometry measurements, all multilayers exhibited a perpendicular magnetic anisotropy with an increase of saturation magnetization with thickness t. From the temperature dependence of the magnetization, well described by a Bloch law, we find that the spin-wave stiffness constant of the [Co/Ni(t)/Co/Pt]×8 multilayers is larger compared to (Co/Ni) multilayers. These multilayers could be the basis for spintronic devices where the reduction of total Pt content could help to reduce the damping constant while keeping the magnetic anisotropy energy relatively high. These are conflicting requirements needed for high performance magnetic memory devices.

Single phase e -Mn4N thin and ultrathin films are grown on MgO(001) using molecular beam epitaxy. Reflection high-energy electron diffraction and out-of-plane X-ray diffraction measurements are taken for each sample in order to determine the in- and out-of-plane strain for each sample. Vibrating sample magnetometry and superconducting quantum interference device measurements, which are performed on the thin and ultrathin films respectively, are used to plot the magnetization of each sample versus both in- and out-of-plane H → -fields and to determine the magnitude of perpendicular magnetic anisotropy in these films. Three significant components of perpendicular magnetic anisotropy are observed in these films and are attributed to sample strain (1 component) and shape (2 components). Among these components, the most significant component 0.8 – 4.9 Merg cm 3 is identified as a second term of shape anisotropy, which possesses a negative linear relationship with sample thickness over the range from 9 nm to 310 nm. Atomic (magnetic) force microscopy measurements show the presence of a surface localized magnetic polarization (22–82 % ), which increases with decreasing thickness, when the net magnetizations of the films are zero. The second term of shape anisotropy as well as the surface localized polarization, which each depend on sample thickness, are each regarded as a consequence of Ising domains overlapping out-of-plane in these films.

The perpendicular magnetic anisotropy (PMA) of the Pd/Co2MnSi(CMS)/Co3O4 and Pd/CMS/Pd/CMS/Co3O4/Pd multilayers has been studied in this paper. The Pd/CMS/ Co3O4 is a “heavy metal (HM)/ferromagnetic (FM) /antiferromagnetic (AFM) oxide” structure that has triple interfacial effects, which is HM/FM, FM/OX and FM/AFM. For Pd (6 nm)/CMS (t nm)/Co3O4 (0.6 nm) /Pd (6 nm) structure, the maximum magnetic anisotropy energy density (Keff) is 0.583 Merg/cm3 at t = 6 nm and the PMA can be maintained with the thickness of the CMS layer in a range of 3.5–8 nm. When the thickness of the Co3O4 layer varied from 0 to 1.3 nm, the multilayer structure also has PMA with 6 nm CMS layer. Inserting a Pd layer in the CMS to form Pd/CMS/Pd/CMS/Co3O4/Pd structure can enhance the PMA and the saturated magnetization. The maximum Keff of the Pd/CMS/Pd/CMS/Co3O4/Pd structure is 0.680 Merg/cm3 by inserting a 0.8 nm Pd layer, which is 15% larger than samples without inserting Pd layer in the CMS. The crystallization quality of Co3O4 relates to the power of sputtering deposition and furthermore affects the flatness of the interface and PMA of the multilayer film.

In this work we have investigated the influence of Ar sputtering pressure ( P Ar ) in the magnetic properties of polycrystalline sputtered Fe0.89Ga0.11 thin films. The structural characterization shows that the samples are composed by several fiber-like crystallographic textures in which the fiber axis is always along the growth direction, whereas their portion weights evolve with P Ar during the sputtering deposition. Magnetometry and ferromagnetic resonance (FMR) experiments evidence the existence of a perpendicular magnetic anisotropy (PMA) that increases systematically for increasing P Ar . By proposing a model that takes into account the interfacial, magnetoelastic and magnetocrystalline contributions to the magnetic free energy, we find that the magnetocrystalline one appears as the main responsible of the increasing PMA. The PMA values estimated from the model predict satisfactorily the experimental values obtained from FMR.

In order to achieve high track density in perpendicular recording, write-field leakage from the main pole to adjacent tracks needs to be minimized. We used a 3-D finite-element method to investigate the optimal writer design, which minimizes fringing fields. We also confirmed the results using experimentally by studying adjacent track interference (ATI) on a spinstand. According to both modeling and experimental data, we found that ATI performance can be clearly improved with a wrap-around-shielded (WAS) writer while maintaining enough write-ability. In order to reduce the fringing field, a WAS having thick throat, high permeability and high saturated magnetic flux density was required. We also confirmed that variations of ATI performance due to flare length distributions can be effectively suppressed with the WAS writer.

The use of patterned media is one of the proposed approaches for extending magnetic storage densities and delaying the problems imposed by the superparamagnetic limit. In this paper, we investigate the reliable recovery of data from patterned media with perpendicular anisotropy using a software tool developed to simulate the read channel. The bit error rate against signal-to-noise ratio (SNR) performance of various partial-response maximum-likelihood (PRML) channels is evaluated. It is shown that the PRML channels for perpendicular recording offer better performance than the conventional channels for longitudinal recording. In addition, simulations reveal that the use of run-length limited encoders and the existence of a soft magnetic underlayer contribute to an improved performance in terms of SNR.

A cylindrical magnetic storage system using perpendicular double-layered media has been developed. CoCrTa/CoZrNb deposited on a rotating cylindrical substrate shows perpendicular anisotropy and magnetic properties, which have almost the same characteristics as conventional disk-media. The fundamental read/write characteristics of perpendicular double-layered cylindrical media were measured using a single-pole-type (SPT) writer with a sliding-contact-type slider and a merged giant magneto-resistive (GMR) reader with a one-pad-type slider designed for use with cylindrical media. Preliminary studies for improving the characteristics of the recording layer are also described.

In this study, the deposition pressure dependence of the compositional ratio, magnetic domain structure, and perpendicular magnetic anisotropy (PMA) of B-containing PrFe- and PrCo-based films, which are rare-earth–transition-metal (RE–TM) films, was investigated. PrFe- and PrCo-based films were fabricated by magnetron sputtering. The film compositions were controlled in a wide range by varying the deposition pressure. On the basis of experimental results, the residual stress of the films was considered to be the possible origin of their PMA. The films showed strong magneto-optical effects over the entire wavelength range of 300–750 nm. Because of the excellent magnetic and magneto-optical (MO) properties of the films, they have high potential for MO applications at wavelengths of red and blue lasers.

Using a silicon micromechanical resonator as a sensitive magnetometer, the authors have studied both experimentally and theoretically the magnetic behavior of two isolated ferromagnetic nanotubes of perovskite La 0.67 Ca 0.33 MnO 3 . The article investigates the specific configuration where a magnetic field H is applied perpendicular to the magnetic easy axis of an isolated nanotube characterized by an uniaxial anisotropy constant K. In this situation, the magnetization M reduces the effective elastic constant k M of the resonator. This softening of the mechanical system is opposed to the hardening effect of M observed in a previous work, where H was applied parallel to the easy axis. Moreover, in this magnetic field configuration two distinct magnetization regimes are manifested, depending on the magnitude of H. For H ⪢ 2 K / M the magnetization is almost parallel to the applied magnetic field and for H ⪡ 2 K / M it is almost parallel to the easy axis of the nanotube. At a certain value of H there is a sharp transition from one regime to the other, accompanied by a peak in the energy dissipation.

Transition shift can create serious timing problems for high density recording environments. However, it is possible to use techniques such as write precompensation to offset the timing error introduced if the magnitude and the behaviour of the transition shift are properly understood. This paper introduces a 3D finite element method (FEM) to analyse the transition shift in perpendicular magnetic recording (PMR) quantitatively, allowing the combinational effects of the transition shifts from non-linear transition shift (NLTS), HTS, and neighbourhood-induced transition shift (NITS) to be examined. The consideration of all contributing factors to the final written transition position is important in determining the precompensation scheme of magnetic data recording, and 3D FEM can facilitate such quantitative analysis.

The microstructure of a CoNiFeB film for a soft magnetic underlayer of perpendicular recording media, which was deposited by electroless plating on a Si wafer, has been investigated by transmission electron microscopy and a three-dimensional atom probe. After the deposition of the CoNiFeB film on a Ni underlayer, H c decreased from about 62 to about 3 Oe. Based on the microstructure observation results, the decrease of H c was concluded to be the result of reduced magneto-elastic energy. The good adhesiveness between the soft underlayer (SUL) and the Si substrate was found to be due to the composition gradient.

The magnetization reversal process in perpendicularly biased [ Pt / Co ] 3 / d Pt Pt/IrMn and in-plane biased Co / d Pt Pt/IrMn multilayers with 0 nm ⩽ d Pt ⩽ 1.2 nm was investigated using Kerr magnetometry and Kerr microscopy. For the system with in-plane magnetic anisotropy, the exchange bias field decreases monotonically with Pt insertion layer thickness, while its coercivity remains constant. The samples with perpendicular magnetic anisotropy, on the other hand, exhibit maximum exchange bias and minimum coercivity for d Pt = 0.1 nm . In both cases, the existence of large exchange bias fields correlates with a high domain density during magnetization reversal. The interface exchange coupling energy is larger for the in-plane biased films than for the perpendicularly biased multilayers.

A soft-magnetic ferrite disk substrate was investigated as an underlayer of perpendicular double layer hard disk media for single-pole heads. Although a soft-magnetic thin-film is generally used for the underlayer, concern about the eddy current effect for a metallic underlayer in high-frequency operations. In order to avoid the eddy current, Co–Cr perpendicular media were prepared on the Mn–Zn ferrite substrate to examine their read/write performance. Experimental results with a single-pole writing head and an MR head showed that the ferrite substrate disk had better writing sensitivity and frequency response owing to its large volume and electrical resistivity.

Output results are presented for a shielded MR head reading from a double-layer, perpendicular medium. The integrals required for an exact Fourier solution are given as rapidly convergent series. An approximation is used to provide accurate PW 50 and D 50 results over a wide range of practical head dimensions. Simple, approximate PW 50 and D 50 formulae are derived and their range of validity discussed.

Conformal mapping was applied to derive the concept of the playback waveform equivalency between a shielded read head and a dual pole head utilized for reading from longitudinal and perpendicular media, respectively. The equivalency relationships between the respective head dimensions were defined. To support the concept in 3D, 3D-boundary element calculations were performed to calculate the sensitivity fields corresponding to both the head types.

In order to prepare the perpendicular magnetic recording tape, a small amount of Ta was added into the Co–Cr films and Kr was used instead of Ar as a sputtering gas. The recording and reproducing characteristics of the Co–Cr–Ta tape were evaluated using a one-half inch VCR. The reproduced output at the recording wavelength of 0.33 μm was 56 nVO-P/(μm T m/s). This value was almost equal to the reproduced output of MP tape at the recording wavelength of 0.66 μm.

To achieve the recording technology over 10 Gb/in 2 , quite short bit cells have to be written and read probably by an MR head. The resolutions of unshielded and shielded MR heads were estimated for perpendicular and longitudinal recording. Moreover, we designed and fabricated some samples of the MR/Inductive heads that have been developed for perpendicular magnetic recording, and evaluated them with a double-layered medium. The shielded MR head offered high D50 of 170 kFRPI and high-density readback signal of 500 kFRPI. However, when the recorded bit length became shorter than the MR-to-shield gap, the shield had little effect and the output of the shielded head was no longer roughly equal to that of the unshielded head. Even unshielded MR head has good high-density recording characteristics in case of the combination with a perpendicular medium.

The error events for PR2ML system in perpendicular magnetic recording using double-layered medium with additive white Gaussian noise, jitter-like noise and distortion due to low frequency cut-off are studied. The result shows that the error event “+−+00” extremely increases as the cut-off frequency becomes high. The error events obtained by computer simulation are also compared with those obtained by the R/W experiments. It is clarified that the simulated error events approximately correspond to the experimental results.

The static equilibrium magnetization and the spin waves of a magnetic stripe are numerically studied: the calculation is based on a finite element method. The variations of the magnetic properties versus the strength of an in-plane magnetic field applied perpendicularly to the stripe are investigated. Two phase transitions, showing critical fields H 1 and H 2 are evidenced: the first one corresponds to the vanishing of the parallel component of the static magnetization at the center of the section, the second one is defined by the vanishing of this component at the corners of the section. These two phase transitions induce a softening of some eigen frequencies as well as a drastic modification of the profile of the lowest eigen modes.

When the thin film of high-quality magnetic fluid is subjected to a perpendicular magnetic field, a separation of particles from the liquid matrix will occur, leading to a phase transition with a phase that is concentrated in particles separating from a dilute phase. The concentrated phase makes up the cylindrical columns that can form two-dimensional lattices. We have explored the field-induced lattices with optical microscopy, digital imaging and computer-video techniques in this study, to classify the ordering property in terms of bond-orientation order.

A model for the behaviour of transverse initial susceptibility as a function of dc applied field is developed for the case of thin films exhibiting simultaneous in-plane and perpendicular anisotropy. It is used to deduce in-plane and perpendicular anisotropy fields in a very simple way from transverse susceptibility measurements made by the transverse Kerr effect. The results obtained are cross-checked by those obtained from magnetization curves.

The dynamic state diagram for spin current-induced magnetization dynamics is presented for an out-of-plane magnetized (perpendicular) polarizer and an in-plane magnetized (planar) free layer as obtained from macrospin simulations. The state boundaries are compared upon using a constant spin polarization factor with an angular-dependent spin polarization factor g ( θ MP ) as introduced by Slonczewski. While two critical boundaries remain unaffected by the angular dependence of the polarization, the transition from precession to an out-of-plane stable state is drastically shifted and shows a strong asymmetry with respect to the sign of the spin-polarized current.

In this work, we have utilized ZnCl 2 –dimethylsulfone (DMSO 2 ) as the electrolyte for preparing a perpendicular Gd x (FeCo) y magnetic thin film by the pulse potential with a voltage of −0.001 V and pulse ratio ( t on / t off ) of 0.1 and 0.2. A perpendicularly magnetic property of the thin film was investigated by alternating gradient magnetometer (AGM). Moreover, a crystal structure and cross-section of the thin film were observed by transmission electron microscope (TEM).

To achieve high-throughput fabrication of Co-Cr/Ni-Fe double-layer perpendicular media, the optimum conditions for continuous preparation and construction of a new dc magnetron sputtering target have been investigated with respect to the aperture shield mask position and the magnetic circuit. The perpendicular magnetic tape media fabricated in a roll-coater equipped with the improved target showed high reproduced voltage at high densities.

To serve the needs of high linear bit density recording and high data transfer rate, a new perpendicular recording hard disk media constitution is proposed. In the new hard disk media, a Co-Cr layer is directly deposited on a soft-magnetic Mn-Zn single-crystal ferrite substrate. The ferrite substrate hard disk showed superior high-frequency response to a conventional Co-Cr/Fe-Ni-Nb double-layered hard disk with glass substrate. This improvement in high frequencies is brought about by suppressing the eddy current losses because of high electric resistivity of the ferrite substrate.

One of the origins of perpendicular magnetic energy of Fe-Zr films may be attributed to the structural inhomogeneity of Fe-rich alloy crystallites in a Fe-Zr amorphous matrix. Fe-Ni-Zr films deposited on PEN tape substrates at about 90°C exhibited large K u with appropriately large 4π M s suitable for flexible recording media.

Future trends for high-density video data storage of 1 T bits/in 3 in multimedia service are discussed in this paper. A magnetic recording tape with CoCrTa/NiFe multilayer has been prepared using a facing targets sputtering system. Read/write characteristics and digital video recording characteristics of this tape have been investigated using a modified conventional VCR. It has been proven that the tape should be highly efficient in high-density recording of 1 T bits/in 3 .

An instrument for magnetic anisotropy determination based on perpendicular magnetization measurement is described. The principal advantages compared with the usual torsion magnetometers are a much simpler construction and operation. In addition it is possible to measure high anisotrpies, the overall sensitivity in torque is ≈ 10 dyne cm. Some experimental torque curves obtained with the apparatus are also given.

CoCrPt– SiO 2 -based granular perpendicular media with dual-Ru intermediate layers were studied in the paper. The effects of gas pressures, such as argon pressure for the top Ru layer, oxygen partial pressure ratio and the total gas pressure for the magnetic layer, on the magnetic properties and recording performance of the media were systematically investigated. The results show that all these gas pressure parameters have significant effects on the magnetic properties and recording performance of the media to different extents. Combined with the results by X-ray diffraction, transmission electron microscopy, magnetic force microscopy, magneto-optical polar Kerr magnetometer and Guzik spin-stand tester, the growth mechanism of the perpendicular media and the functions of the gas pressure parameters for certain individual layer were demonstrated.

SmCo5 thin films with Cu seedlayer exhibiting perpendicular magnetic anisotropy were studied. The perpendicular magnetic anisotropy was enhanced using the Sm–Co layer formed by laminating Co and Sm sub-layers alternately. The Co/Sm laminate structure promoted the crystallization of SmCo5 and the preferred orientation of its c-axis. The perpendicular magnetic anisotropy was further improved by suppressing the surface roughness of the Cu seedlayer. The SmCo5 thin film prepared in this study possesses an adequate corrosion resistance when judged by an electrochemical analysis.

Applying a magnetic field on the magnetic fluid thin film perpendicularly, leads a phase separation that is concentrated in particles separating from a dilute phase. The concentrated phase forms cylindrical columns that construct two-dimensional lattices. This kind of artificial lattice is a novel mesoscopic system and has been explored with optical microscope, CCD, and digital imaging analysis. We explore the ordering evolution of the two-dimensional extraordinary lattice by varying the applied field. The ordering of these lattices is analyzed in terms of translational and bond-orientation correlation functions to address the two-dimensional melting.

The magnetoresistance (MR) of layered metal systems with the current in a direction perpendicular to the plane of the layers (CPP) is studied. The technique for measuring the resulting very small resistances utilises a SQUID to act as a high-precision current comparator. The samples are Co/Cu multilayers grown by molecular beam epitaxy (MBE) in ultrahigh vacuum (UHV). Perpendicular resistance measurements are reported for Nb/Cu/X/Cu/Nb where X is the Co/Cu multilayer. The Co is fixed at a nominal value of 1.5 nm while the Cu is varied between 1 and 5 nm. These measurements show large oscillations in the CPP-MR as the Cu thickness in increased. A comparison is made between MBE and sputtered samples.

A spinning-sample magnetic alignment (SSMA) method has been used to align the basal planes of non-uniaxial Y2Fe17 and Gd2Fe17 compounds parallel to each other. The magnetocrystalline anisotropy fields of magnetically aligned Y2Fe17 and Gd2Fe17 were determined, for the first time, in the temperature range from 4.2 K to the Curie temperature using the SPD technique in a pulsed-field magnetometer.

Multilayered magnetic thin films, grown on mica by vapour deposition, were studied by X-ray diffraction, electron microscopy, vibrating sample and torque magnetometry techniques. The various structural characteristics were found to affect strongly the magnetic properties. Depending on the profile of the modulation period, for Pd m -Ni or Cu m -Ni n , perpendicular anisotropy and enhanced magnetisation were observed as well as a peculiar reversal of the hysteresis.

The Ar pressure dependence of both the microstructure and the magnetic properties of sputter-deposited Co-Cr film is investigated. As the Ar pressure decreases, the structural binding between columns in the film becomes denser and stronger. The columnar structure has no relation to the crystal orientation. A domain structure change is suggested.

Thin films of Nd-Fe prepared by rf sputtering are shown to exhibit marked perpendicular anisotropy. Hysteresis loops with a sqaureness ratio of essentially 1.0 with large coercivities and significant polar Kerr rotations are reported for films with 60 at% Nd.

Multilayered films consisting of layer stacks with different anisotropies are studied by vector magnetometry i.e. simultaneous measurement of the components M x , M y along and perpendicular to the applied field respectively. The quantity M x 2 + M y 2 is used as measure of the homogeneity of the reversal. For the [Co(6 A)/Pt(15 A)] 4 /(Pt(s))/[Co(10 A)/Pt(15 A)] 4 with s = 0–45 A series consisting of a perpendicular anisotropy bottom four-bilayer-stack coupled to a planar anisotropy top four-bilayer-stack a peak of the M y component is clearly observed at the M x coercivity. This is a sign of homogeneous reversal but it can be shown that similar effects can arise by decoupling of two layers with different (in-plane/perpendicular) anisotropies which is the case for s > 15 A. In order to study the latter effect, a [Co(6 A)/Pt(15 A)] 4 /W(15 A)/Co(24 A) sample is used as a reference as it consists of a perpendicular anisotropy bottom four-bilayer-stack coupled to a vanishing anisotropy top Co layer through a W layer (which creates a magnetically inactive interface permitting only dipolar coupling). In contrast for [Co(5 A)/Pt(10 A)] 6 /Pt(s)/[Ni(15 A)/Pt(5 A)] 6 series consisting of two different coercivity stacks which both have perpendicular anisotropy the decoupling does not manifest by appearance of peaks in the M y component.

In order to analyze the performance of magnetic device which operate at high temperature and high pressure, such as submersible motor, oil well transformer, the electrical resistivity of non-oriented silicon steel sheets is necessary for precise analysis. But the reports of the examination of the measuring method suitable for high temperature up to 180 °C and high pressure up to 140 MPa are few. In this paper, a measurement system based on four-probe method and Archimedes spiral shape measurement specimens is proposed. The measurement system is suitable for measuring the electrical resistivity of unconventional specimens under high temperature and high pressure and can simultaneously consider the influence of the magnetic field on the electrical resistivity. It can be seen that the electrical resistivity of the non-oriented silicon steel sheets will fluctuate instantaneously when the magnetic field perpendicular to the conductive path of the specimens is loaded or removed. The amplitude and direction of the fluctuation are not constant. Without considering the effects of fluctuations, the electrical resistivity of the non-oriented silicon steel sheets is the same when the magnetic field is loaded or removed. And the influence of temperature on the electrical resistivity of the non-oriented silicon steel sheet is still the greatest even though the temperature and the pressure are coupled together. The measurement results also show that the electrical resistivity varies linearly with temperature, so the temperature coefficient of resistivity is given in the paper.

The effect of the applied tensile stress during annealing on the structural anisotropy expressed by the shift in peak position is studied in situ using synchrotron XRD. The evolution of the diffraction spectra during in situ nanocrystallization for ribbons annealed with and without stress is also shown. There is a clear difference between the peaks in the parallel and perpendicular directions in the d-spacing between (2 0 0) planes for the stress-annealed sample while the difference is somewhat insignificant for the sample annealed without stress. The structural anisotropy for the sample annealed without stress decreases from 0.01° to 0.001° while the structural anisotropy first increased from 0.48° to 0.54° between 675 s and 828 s, decreased gradually to 0.5° after 2187 s, then decreased sharply to 0.43° as the sample is cooled to room temperature for the stress annealed sample. The (2 0 0) lattice spacing is elongated in the direction parallel to the applied stress for the stress-annealed sample. No observed elongation in the (2 0 0) lattice spacing for the sample annealed without stress. This shows that the origin of the stress-induced anisotropy is in agreement with the magnetoelastic theory.

A new colloidal composite formed by specially synthesized dimethylphenyl ferrite particles and a nematic liquid crystal (LC) is presented. By applying a small magnetic field during polarizing optical microscopy observations, it was found that the magnetic moment of the synthesized ferrite is perpendicular to the director of the LC. The optical transmission of laser light across the ferronematic was investigated under magnetic field. The critical magnetic field corresponding to the Freedericksz transition was obtained and discussed according to the Burylov and Raikher theory.

High-frequency permeability spectra of magnetic films were measured over a wideband frequency range of 0.1–30 GHz using a shielded and short-circuited microstrip line jig. In this measurement, spurious resonances had to be suppressed up to the highest frequency. To suppress these resonances, characteristic impedance of the microstrip line should approach 50 Ω at the junction between connector and microstrip line. The main factors dominating these resonances were structures of the jig and the sample. The dimensions were optimized in various experiments, and results demonstrated that the frequency could be raised to at least 20 GHz. For the transverse electromagnetic mode to transmit stably along the microstrip line, the preferred sample was rectangular, with the shorter side parallel to the line and the longer side perpendicular to it, and characteristic impedance strongly depended on the signal line width of the jig. However, too small a jig and sample led to a lower S/N ratio.

Magnetic skyrmions are topological spin textures that have attracted significant attention owing to their diverse physical characteristics. Recently, various applications utilizing the Brownian motion of skyrmions have been reported. However, the diffusion of skyrmions is suppressed by pinning sites in magnetic thin films, which can limit computing speed. In this paper, we explore the stochastic dynamics and diffusion coefficient of skyrmions under a perpendicular alternating current (AC) magnetic field. The skyrmion diffusion coefficient increased exponentially as the AC magnetic field was increased owing to the stretching motion of the string-shaped skyrmions. This study may provide a technological framework for the realization of low-power-consumption Brownian devices.

The transmission properties of a one-dimensional photonic crystal containing graphene mono-layers are studied using the transfer matrix method. It is shown that the structure can be used as a polarization-selective nonreciprocal device which discriminates between the two circularly polarized waves with different handedness impinging in the same direction. This structure may be utilized in designing optical isolators for the circularly polarized waves due to the gyrotropic behavior of the graphene mono-layers under the perpendicularly applied external magnetic field. Moreover, the effect of an external magnetic field and the chemical potential of the graphene mono-layers on the band gap of the structure are investigated.

We developed an advanced particulate magnetic tape using fine barium ferrite (BaFe) particles for magnetic-tape storage systems. The new tape showed a signal-to-noise ratio (SNR) that was 3.5 dB higher than that of the commercially available BaFe tape used for the Linear Tape Open generation 6 tape-storage system, at a linear density of 300 kfci measured with a giant magnetoresistive head with a reader width of 0.45 µm. Such significant increase in SNR was achieved by reducing the magnetic particle volume from 1950 to 1350 nm 3 , while maintaining a sufficiently high thermal stability, improving the perpendicular squareness ratio from 0.66 to 0.83, and improving the surface roughness from 2.5 to 2.0 nm when measured by atomic force microscopy and from 2.4 to 0.9 nm when measured by optical interferometry. This paper describes the characteristics of the new BaFe particles and media, which are expected to be employed for future high-capacity linear-tape systems.

A scanning magnetic microscope based on an off-diagonal magnetoimpedance sensor is presented. As a sensor, we use a 4 mm segment of glass covered microwire, having a metallic core diameter of 13.5 μm and CoFeCrSiB composition and a pick-up coil wound around the microwire containing 70 turns. The magneto-impedance sensor is fixed perpendicular to the surface of the sample, in such a way that the distance between the tip of the microwire and the sample is about 200 μm. The relative movement of the sample and the GMI sensor is carried out using a non-magnetic X-Y positioner. Measurements are taken inside the magnetic screen. For test measurements, samples in the form of the letters IWMW – of the conference abbreviation are used. The samples were made based on thin copper wire, Fe-rich amorphous ferromagnetic microwires and printed by laser-jet printer. Clear magnetic images were obtained on all samples, which demonstrates the high practical potential of the proposed method.

Micromagnetic simulations have been performed to investigate the suppression of the skyrmion Hall effect in nanotracks with their magnetic properties strategically modified. In particular, we study two categories of magnetically modified nanotracks. One of them, repulsive edges have been inserted in the nanotrack and, in the other, an attractive strip has been placed exactly on the longest axis of the nanotrack. Attractive and repulsive interactions can be generated from the engineering of magnetic properties. For instance, it is known that the skyrmion can be attracted to a region where the exchange stiffness constant is decreased. On the other hand, the skyrmion can be repelled from a region characterized by a local increase in the exchange stiffness constant. In order to provide a background for experimental studies, we vary not only the magnetic material parameters (exchange stiffness, perpendicular magnetocrystalline anisotropy and the Dzyaloshinskii-Moriya constant) but also the width of the region magnetically modified, containing either a local reduction or a local increase for each one of these magnetic properties. In the numerical simulations, the skyrmion motion was induced by a spin-polarized current and the found results indicate that it is possible to transport skyrmions around the longest axis of the nanotrack. In practice, the skyrmion Hall effect can be completely suppressed in magnetic nanotracks with strategically modified magnetic properties. Furthermore, we discuss in detail 6 ways to suppress the skyrmion Hall effect by the usage of nanotracks with repulsive edges and nanotracks with an attractive strip.